Unilateral Approach to Bilateral Clipping of Intracranial Aneurysms: A Case Series

Unilateral Approach to Bilateral Clipping of Intracranial Aneurysms: A Case Series | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Unilateral Approach to Bilateral Clipping of Intracranial Aneurysms: A Case Series Chaurasia Puja, Jha Rajiv, Alfredo Conti, Bipin Chaurasia This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6371541/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Multiple intra-cranial aneurysms whose incidence ranges 7–45% pose significant management issues, often due to the necessity of multiple sequential treatments. We present a consecutive series of patients undergoing unilateral surgical approach to clipping of bilateral intracranial aneurysms and their peri-operative outcome. Methods This is a retrospective case series of ten patients who presented to the National neurosurgical referral center, National academy medical sciences, Nepal between March 2020 and April 2024 with multiple aneurysms. The patients were evaluated and diagnosed based on clinical judgement as well as using CT/MR/DS angiography as imaging modality. Patients admitted with diagnosis of multiple aneurysms, who underwent unilateral approach to bilateral clipping of aneurysms, were included in the study. Results 10 patients underwent unilateral approach to bilateral clipping of intracranial aneurysms. Nine aneurysms were clipped without intra-operative complications, one had mild intra-operative rupture of the ipsilateral aneurysm. The post-operative CT angiography showed obliteration of ipsi- and contralateral aneurysms with no additional morbidity due to prolonged and more extensive dissection. Morphological parameters used to evaluate feasibility of bilateral clipping included limited length of the contralateral A1-M1, size and morphology of the aneurysms, tightness of the subarachnoid space due to hemorrhagic adhesion. Conclusions Contralateral approach is an effective technique to treat bilateral aneurysms with a single surgery, being cost-effective with a reasonable risk profile, provided that a correct preoperative planning is done. cerebral aneurysm approach microsurgery clipping outcome Figures Figure 1 Figure 2 Introduction Intracranial aneurysms are common vascular malformations presenting as multiple lesions in 7–45% of cases. Bilateral aneurysms pose a unique challenge due to the need for multiple treatments involving bilateral craniotomies or combined endovascular and surgical treatments. As an alternative to this strategy, a single unilateral craniotomy for the clipping of both ipsilateral and contralateral aneurysms is possible [ 1 , 2 ], as a technique that reduces surgical burden while maintaining the efficacy of treatment [ 3 ]. The feasibility of this approach depends on various factors, including aneurysm size, location, and the degree of vascular tortuosity, always bearing the preferences and experience of the neurosurgeon in mind [ 4 ]. Meticulous preoperative planning by three-dimensional digital subtraction angiography (3D-DSA), allow a preoperative evaluation of the feasibility of this strategy increasing the safety and efficacy of the procedure. This study explores the clinical and surgical outcomes of a consecutive series of patients who underwent unilateral craniotomy for bilateral aneurysm clipping, with a focus on neurological outcomes, procedural challenges, and postoperative complications. Materials and Methods Study Cohort This retrospective case series includes 10 patients treated at the National Neurosurgical Referral Center, National Academy of Medical Sciences, Nepal between March 2020 and April 2024. All patients were diagnosed with multiple intracranial aneurysms through a combination of clinical assessment and imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and digital subtraction angiography (DSA). A second series of 10 patients undergoing bilateral surgical treatment was collected for comparison of radiological characteristics . Variables Patients were selected based on specific inclusion criteria, which required adequate preoperative imaging confirming the feasibility of the contralateral approach, a favorable surgical corridor, and the absence of significant brain swelling or midline shift. The severity of subarachnoid hemorrhage (SAH) was classified using the Hunt and Hess (HH) grading scale, while the modified Miller Fisher (MF) [ 8 ] grading system was used to predict the risk of symptomatic vasospasm. Neurological outcomes were assessed using the modified Rankin Scale (mRS) before and after surgery. Radiological Characterization The relevant radiographic images (computed tomographic angiography [CTA], magnetic resonance angiography, digital subtraction angiography) were retrieved from the hospital’s digital archiving system. For all patients, we (a) measured the maximal length, neck width, and size of the aneurysms and (b) evaluated the presence of calcifications, irregularities, complex anatomy and secondary pouches, shape (saccular vs fusiform), and the projection of the aneurysm dome in relation to the parent artery and sylvian fissure [ 5 – 7 ]. Radiological Evaluation of the Microsurgical Corridor We measured the height in millimeters of each internal carotid artery (ICA) bifurcation above the planum sphenoidale, as well as the lengths of the contralateral anterior cerebral artery proximal segment (A1) and the middle cerebral artery proximal segment (M1). Additionally, the distance between both ICA bifurcations and their respective ipsilateral MCA aneurysms were recorded. We determined these distances via coronal CTA at the level of the ICA bifurcation and also compared them with 3-D CTA reconstruction models Treatment The surgical procedure involved a pterional craniotomy on the non-dominant hemisphere or the side with the aneurysm being at higher risk of rupture. After dural opening, cerebrospinal fluid (CSF) drainage was performed to facilitate brain relaxation. Aneurysms were clipped in sequence, with ipsilateral aneurysms addressed first. The contralateral aneurysms were then accessed by retracting the frontal lobe and utilizing the interoptic, prechiasmatic, or trans-sylvian corridor for visualization and dissection. Postoperative angiography was performed in all patients to confirm complete aneurysm occlusion (Fig. 1 ). Outcome The outcome for both groups was assessed by a neurosurgeon at discharge and at 3 months follow-up. The outcome was classified according to the modified Rankin Scale (mRS) as good (mRS 0–3) or poor (mRS 4–6), based on the ability to walk without assistance. Ethics Informed consent was obtained from all participants in accordance with ethical guidelines. Given the retrospective nature of this study, ethical committee approval was waived, as permitted by local institutional review board regulations. Results Clinical Characteristics of Patients The study cohort consisted of ten patients, including eight females and two males, with a mean age of 51.2 years. Table 1 summarizes demographic and clinical characteristics of patients. Nine patients had aneurysms located in the anterior circulation, while one had an aneurysm in the posterior circulation. Preoperative imaging revealed SAH in nine cases, with one patient presenting with SAH complicated by intracerebral hemorrhage (ICH). Table 1 Essential clinical characteristics of patients at presentation Patient Age Sex Presentation H&H MF 1 57 F SAH 2 2 2 36 M SAH 3 3 3 60 M SAH 2 2 4 46 F SAH 2 2 5 56 F SAH 2 2 6 51 F SAH 3 2 7 34 F SAH + ICH 2 4 8 66 F SAH 4 3 9 50 F SAH 2 2 10 56 F SAH 3 2 Abbr.: SAH: subarachnoid hemorrhage. ICH: intracerebral hemorrhage. HHç Hunt Hess. MF: Miller Fisher Neurological grading using the Hunt and Hess scale indicated that six patients were classified as grade 2, three as grade 3, and one as grade 4 at the time of admission. Modified Miller Fisher grading demonstrated a predominance of grade 2 findings, suggesting a moderate risk of vasospasm. The timing of surgery ranged from two to seven days after ictus, with most procedures performed between the second- and fourth day following hemorrhage. Size and Morphology of Aneurysms Table 2 summarizes the distribution of size, morphology, projections, and characteristics of the aneurysms. The median neck diameter of the ipsilateral aneurysm was 3.55 mm (range: 3–5 mm) and the median size of the aneurysm dome was 6.1 mm (range: 5–10 mm), whereas the median neck diameter of the contralateral aneurysm was 2.45 mm (range: 2–3 mm) and the median length of then contralateral aneurysm dome was 4.8 mm (range: 4–6 mm). All contralaterally approached aneurysms were unruptured. Table 2 Summary of the distribution of size, morphology, projections, and characteristics of the aneurysms Patient Neck size of ipsilateral aneurysm (mm) Dome size of ipsilateral aneurysm (mm) Shape Margins Projection Neck size of contralateral aneurysm (mm) Dome size of contralateral aneurysm (mm) Shape Margin Projection 1 3 6 lobulated Irregular Superior 2 5 Single sac unruptured regular Superolateral 2 3.5 5 lobulated Irregular Anteroinferior 2 4 Single sac unruptured regular Anterosuperior 3 3 5 Single sac ruptured Regular Posterior 3 5 Single sac unruptured regular Superomedial 4 5 10 Single sac ruptured Regular Inferolateral 3 6 Single sac unruptured regular Superomedial 5 4 6 Single sac ruptured Irregular Anterolateral 2 5 Single sac unruptured regular Anterior 6 3 5 Single sac ruptured Irregular Anteroinferior 2.5 5 Single sac unruptured regular Anteroinferior 7 3.5 6 Single sac ruptured Irregular Anterior 3 5 Single sac unruptured regular Anterolateral 8 3 5 Single sac ruptured Irregular Superior 2 4 Single sac unruptured regular Anterior 9 3.5 6 Single sac ruptured Irregular Anteroinferior 3 5 Single sac unruptured regular Anterosuperior 10 4 7 Single sac ruptured irregular Superior 2 4 Single sac unruptured regular Anterolateral Radiological Characteristics of Vessels Anatomy and Microsurgical Corridor Morphological characteristics of aneurysms were unilobar (80%), multilobar (20%). None presented calcifications or complex anatomy including direct branching from the aneurysm sac. To better understand characteristics of the surgical corridor for unilateral approach, we compared anatomical features including length of ipsilateral ICA, ipsi- and contralateral A1, contralateral M1 and distance of ipsilateral ICA bifurcation from the contralateral aneurysm and compared measures with those of a second population of patients, retrospectively selected, with bilateral aneurysm but undergoing bilateral surgical treatment. Table 3 summarizes relevant data of all 20 patients. Table 3 Summary of Aneurysm location and distribution of length of ipsilateral ICA, ipsi- and contralateral A1, contralateral M1 and distance of ipsilateral ICA bifurcation from the contralateral aneurysm in patients undergoing unilateral or bilateral approach Patient No. Approach Ipsilateral aneurysm (ruptured) Contralateral aneurysm (unruptured) ICA length ipsilateral (mm) A1 segment (ipsilateral/contralateral) (mm) Distance from ipsilateral bifurcation to contralateral aneurysm (mm) 1 Unilateral Right MCA ACA (A2) 36 12/10 34 2 Unilateral Right MCA MCA (M1) 24 10/8 30 3 Unilateral Right MCA ICA-PCOM 26 10/8 30 4 Unilateral Left MCA ICA 30 10/9 32 5 Unilateral Right ACOM ACA (A2) 25 10/8 34 6 Unilateral Left MCA MCA 27 8/7 31 7 Unilateral Right ICA MCA 23 8/7 34 8 Unilateral Right MCA MCA 22 7/7 35 9 Unilateral Left MCA MCA(M1) 22 7/7 34 10 Unilateral Left ACOM, ICA ICA 26 11/9 27 11 Bilateral Left ICA Right Pericallosal 22 10/12 61 12 Bilateral Right ICA Left MCA 20 10/11 57 13 Bilateral Right ACA (A2) Left MCA (M3) 22 14/13 64 14 Bilateral Right ICA-PCom Left MCA (M3) 18 10/12 62 15 Bilateral Right ACA Left ACA 24 17/15 59 16 Bilateral Right ICA Left A2-A3 21 14/15 60 17 Bilateral Right MCA Left ACA (A4) 23 15/15 62 18 Bilateral Right choroidal Left M2 23 13/14 54 19 Bilateral Left supracallosal (A4) Right MCA (M3) 28 6/5 53 20 Bilateral Right ICA-PCom Left ACA (A2-A3) 30 15/13 50 Table 4 summarizes the median and interquartile range (IQR) for each surgical corridor variable by surgical approach. Median length of the ICA was 25.5mm; IQ 3.5 in the unilateral craniotomy group and 22.5mm, IQR 2.5mm, in the bilateral craniotomy group. Median length of the ipsilateral A1 was 10mm, IQR 2, in the unilateral craniotomy group and 13.5mm, IQR 4.75mm, in the bilateral craniotomy group. Median length of the contralateral A1 was 8mm, IQ 1.75, in the unilateral craniotomy group and 13mm, IQ 2.75mm, in the bilateral craniotomy group. The median distance of the contralateral aneurysm from the ipsilateral ICA bifurcation was 33mm, IQR 3.75mm, in the unilateral craniotomy group and 50.5mm, IQR 7mm, in the bilateral craniotomy group (Fig. 1 ). Table 4 Median and interquartile range (IQR) for each surgical corridor variable by surgical approach. Variable Approach Median IQR ICA Length Unilateral craniotomy 25.50 3.50 ICA Length Bilateral craniotomy 22.50 2.50 A1 Segment (Ipsilateral) Unilateral craniotomy 13.50 4.75 A1 Segment (Ipsilateral) Bilateral craniotomy 10.00 2.00 A1 Segment (Contralateral) Unilateral craniotomy 13.00 2.75 A1 Segment (Contralateral) Bilateral craniotomy 8.00 1.75 Distance to Contralateral Aneurysm Unilateral craniotomy 59.50 7.00 Distance to Contralateral Aneurysm Bilateral craniotomy 33.00 3.75 Table 4 Surgical approach and patient’s outcome Ictal day Approach Ipsilateral aneurysm (ruptured) Contralateral aneurysm (unruptured) Symptomatic Vasospasm(yes/no) Hospital stay Outcome 2 Right MCA ACA (A2) No 8 Good 2 Right MCA MCA (M1) No 9 Good 3 Right MCA ICA-PCOM No 12 Good 4 Left MCA ICA No 14 Good 3 Right ACOM ACA (A2) No 10 Good 6 Left MCA MCA No 10 Good 3 Right ICA MCA No 9 Good 2 Right MCA MCA No 8 Good 3 Left MCA MCA(M1) No 12 Good 7 Left ACOM, ICA ICA Yes 4 Poor The statistical analysis showed no significant difference of ICA length in the two groups (P = 0.08). On the other hand, ipsilateral A1 length was shorter in the unilateral group (P = 0.03), so well as the contralateral A1 length (P = 0.002), and the distance between the ipsilateral ICA to contralateral aneurysm (P = 0.002) (Table 5 ) Table 5 Mann-Whitney U tests were used to compare distributions between the two surgical approaches Variable U Statistic P-Value ICA Length 73.00 0.0869 A1 Segment (Ipsilateral) 22.00 0.0334 A1 Segment (Contralateral) 10.00 0.0026 Distance to Contralateral Aneurysm 0.00 0.0002 Treatment and Outcome All patients underwent successful clipping of ipsi- and contralateral aneurysms. Postoperative angiography confirmed complete occlusion in all cases. One patient experienced a mild intraoperative ipsilateral aneurysm rupture, which was promptly managed with temporary clipping and controlled hypotension. Severe vasospasm was observed in one patient postoperatively, leading to mortality on the third postoperative day despite aggressive medical management. The remaining nine patients demonstrated favorable neurological recovery, with an improvement in mRS scores at follow-up (table 6). The mean hospital stay was 9.6 days, reflecting a relatively expedited recovery process compared to traditional bilateral craniotomy approaches. Discussion The management of multiple intracranial aneurysms remains a subject of debate, with surgical clipping and endovascular coiling being the two primary treatment modalities. While endovascular coiling offers a minimally invasive alternative, it is often limited by anatomical constraints, particularly in cases of wide-necked aneurysms or those with complex branching patterns. Microsurgical clipping, on the other hand, provides definitive aneurysm occlusion and remains the preferred approach in most patients with ruptured aneurysms. In general, it is widely accepted to clip all accessible aneurysms through a single approach [ 8 – 10 ]. Nonetheless, the optimal strategy depends on the clinical condition of the patient, radiological parameters of the aneurysms and the microsurgical corridors, resources and previous experience of the surgeon and overall Institution. A unilateral approach to bilateral aneurysm clipping offers several advantages, including the elimination of a second craniotomy, reduced operative morbidity, and shorter hospitalization. All aneurysms treated through a contralateral approach in our series were unruptured, in concordance with previous literature underscoring that ruptured aneurysms should be approached from the ipsilateral side [ 8 , 11 ]. All aneurysms treated in this series were smaller than 15 mm. According to previous authors, the size of the aneurysm for safe contralateral clipping should be less than 15 mm [ 8 – 12 ]. Complex aneurysms including multilobar, calcified, those for which direct branching from the sac is suspected, as well as those for which a difficult dissection is predictable should be treated by ipsilateral approach [ 13 ]. Furthermore, a contralateral microsurgical approach should not be attended in patients presenting with severe SAH, tight brain, and edema; avoiding the risk to produce additional injuries to the surrounding neurovascular structures because of excessive brain retraction and difficult dissection. Adequate brain relaxation is critical for safe contralateral exposure, and this was achieved through CSF drainage, mannitol administration, and controlled anesthesia to optimize brain compliance. The choice of surgical corridor depends on the location of the contralateral aneurysm. The distance of dissection and the size of the contralateral surgical corridor depend on the length of both A1 and contralateral M1 segments. In our series of contralaterally approached aneurysms, the median A1 length of 14.22 mm (range: 12-16.1 mm) and M1 length of 14.97 mm (range: 12.2–17 mm) agreed with previous anatomic and radiological findings. [ 8 , 14 – 17 ]. The median distance of the contralateral aneurysm from the ipsilateral ICA bifurcation was 33mm, IQR 3.75mm. When compared with patients undergoing bilateral craniotomy, this distance was 50.5mm, IQR 7mm (P = 0.002) (Fig. 1 ). Our results suggest that we can consider 30–35 mm reasonable for attempting bilateral clipping. Nonetheless, independently from those measures, an M1 and MCA bifurcation aneurysm neck may remain only approximately 1.5 cm and 3 cm away from the anterior communicating artery, as the approach is from more anterior than lateral, and the absolute distance can be possibly less than the sum of the lengths of A1 and M1, making preoperative measurements not necessarily an absolute indication not to attempt bilateral clipping. Understandably, a greater work and attention in opening sylvian fissures is required, because this needs to be more extensive and distal. As a narrative notice, we perceived that a contralateral MCA trunk directing downward increased the feasibility to expose the aneurysm while more distally placed MCA bifurcations are curved around the insula making their exposure difficult because a direct line of sight is lost for distally placed bifurcations. One of the disadvantages of the contralateral approach is the need of frontal lobe retraction. Nevertheless, it should be noted that olfactory dysfunction is recorded in 58% in ipsilateral pterional craniotomy, suggesting a high risk of anosmia in bilateral approaches [ 18 ]. The internal carotid artery (ICA) bifurcation represents the highest point of the circle of Willis (Fig. 2), and its height may be related to the need of frontal lobe retraction for aneurysms beyond the contralateral ICA bifurcation. In our series, a median height of the ICA bifurcation of 50.72 mm (range: 35.8–63 mm) allowed a safe approach without excessive frontal lobe retraction. Despite the technical complexity, the overall complication rate in this study was low. One case of intraoperative rupture was successfully managed, and only one patient succumbed to vasospasm-related complications. These findings align with previous reports suggesting that unilateral clipping can be performed safely in appropriately selected cases. Altogether, the abovementioned parameters serve as a guide for the preoperative selection of the contralateral approach for bilateral aneurysms and to support a policy to perform a unilateral approach from the first attempt provided that the surgical team has extensive experience in microsurgical techniques. The limitations of this study include its small sample size and retrospective design, which may limit the generalizability of the findings. Additionally, long-term follow-up was not included in the present analysis, making it difficult to assess the potential for aneurysm recurrence or delayed complications. Future studies with larger patient cohorts and prospective designs will be essential to further validate the safety and efficacy of this approach. Conclusion A unilateral craniotomy for bilateral aneurysm clipping is a viable and effective alternative to traditional staged surgeries, offering reduced morbidity and hospital stay. This technique requires careful patient selection, precise preoperative planning, and advanced microsurgical skills to ensure favorable outcomes. While the approach is not universally applicable, it represents a valuable addition to the armamentarium of neurosurgeons managing complex aneurysm cases. Further research and long-term follow-up studies are warranted to establish its broader applicability and refine surgical strategies. Declarations Ethics Informed consent was obtained from all participants. This consent included consent to participate any clinical retrospective study and consent to publish results. Given the retrospective nature of this study, ethical committee approval was waived, as permitted by local institutional review board regulations (National Academy of Medical Sciences of Kathmandu [NAMSK] Ethical Committee). Availability of data and materials Clinical data public use is restricted Funding : This research was funded by Next Generation EU – PNRR M6C2, project number: PNRR-TR1-2023-12377246 Informed Consent Statement: Written informed consent has been obtained from the patient to publish this paper Conflicts of Interest: The authors declare no conflicts of interest References Bishnoi I (2021) Contralateral Aneurysm Clipping. In: Kato Y, Zhang X, Dai J, Ansari A (eds) Recent Progress in the Management of Cerebrovascular Diseases. Springer, Singapore. https://doi.org/10.1007/978-981-16-3387-4_11 Muirhead WR, Layard Horsfall H, Khan DZ, Koh C, Grover PJ, Toma AK, Castanho P, Stoyanov D, Marcus HJ, Murphy M (2022) Microsurgery for intracranial aneurysms: A qualitative survey on technical challenges and technological solutions. Front Surg 9:957450. 10.3389/fsurg.2022.957450 PMID: 35990100; PMCID: PMC9386123 Panigrahi M, Patel C, Koradia P, Chandrasekhar YBVK (2022) Contralateral Clipping of Multiple Intracranial Aneurysms. Adv Tech Stand Neurosurg. ;44:161–173. 10.1007/978-3-030-87649-4_8 . PMID: 35107678 Arrese I, Sarabia R (2012) Contralateral approach for middle cerebral artery aneurysms with long M1 segment: report of 2 cases. Neurocirugia (Astur) 23(3):122–126. 10.1016/j.neucir.2012.02.001 Epub 2012 May 2. PMID: 22561020 Dashti R, Hernesniemi J, Niemela M et al (2007) Microneurosurgical management of middle cerebral artery bifurcation aneurysms. Surg Neurol 67(5):441–456 Dashti R, Rinne J, Hernesniemi J et al (2007) Microneurosurgical management of proximal middle cerebral artery aneurysms. Surg Neurol 67(1):6–14 Elsharkawy A, Lehecka M, Niemela M et al (2013) A new, more accurate classification of middle cerebral artery aneurysms: computed tomography angiographic study of 1,009 consecutive cases with 1,309 middle cerebral artery aneurysms. Neurosurgery 73(1):94–102 discussion 102 Rodriguez-Hernandez A, Gabarrós A, Lawton MT (2012) Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique. Neurosurgery 71(1 suppl operative):116–123 discussion 123–124 McMahon JH, Morgan MK, Dexter MA (2001) The surgical management of contralateral anterior circulation intracranial aneurysms. J Clin Neurosci 8(4):319–324 Inci S, Akbay A, Ozgen T (2012) Bilateral middle cerebral artery aneurysms: a comparative study of unilateral and bilateral approaches. Neurosurg Rev 35(4):505–517 discussion 517–518 de Oliveira E, Tedeschi H, Siqueira MG et al (1996) Anatomical and technical aspects of the contralateral approach for multiple aneurysms. Acta Neurochir (Wien) 138(1):1–11 discussion 11 de Sousa AA, Filho MA, Faglioni W Jr, Carvalho GT (2005) Unilateral pterional approach to bilateral aneurysms of the middle cerebral artery. Surg Neurol 63(suppl 1):S1–S7 Andrade-Barazarte H, Kivelev J, Goehre F, Jahromi BR, Noda K, Ibrahim TF, Kivisaari R, Lehto H, Niemela M, Jääskeläinen JE, Hernesniemi JA (2015) Contralateral Approach to Bilateral Middle Cerebral Artery Aneurysms: Comparative Study, Angiographic Analysis, and Surgical Results. Neurosurgery. ;77(6):916 – 26; discussion 926. 10.1227/NEU.0000000000000930 . PMID: 26308631 Rodriguez-Hernandez A, Gabarrós A, Lawton MT (2012) Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique. Neurosurgery 71(1 suppl operative):116–123 discussion 123–124 Inci S, Akbay A, Ozgen T (2012) Bilateral middle cerebral artery aneurysms: a comparative study of unilateral and bilateral approaches. Neurosurg Rev 35(4):505–517 discussion 517–518 Oshiro EM, Rini DA, Tamargo RJ (1997) Contralateral approaches to bilateral cerebral aneurysms: a microsurgical anatomical study. J Neurosurg 87(2):163–169 Rhoton AL Jr (2002) The supratentorial arteries. Neurosurgery 51(4 suppl):S53–S120 Cho et al (2017) Comparison of Unilateral and Bilateral Craniotomy for the Treatment of Bilateral Middle Cerebral Artery Aneurysms: Anatomic and Clinical Parameters and Surgical Outcomes. World Neurosurg 108:627–635 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6371541","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":475598427,"identity":"d84658fe-cf2a-486c-bec5-411ec14bb151","order_by":0,"name":"Chaurasia Puja","email":"","orcid":"","institution":"National academy of medical sciences","correspondingAuthor":false,"prefix":"","firstName":"Chaurasia","middleName":"","lastName":"Puja","suffix":""},{"id":475598428,"identity":"2ea1bb8b-2c91-466c-ae66-5bc92ad8aabf","order_by":1,"name":"Jha Rajiv","email":"","orcid":"","institution":"National academy of medical sciences","correspondingAuthor":false,"prefix":"","firstName":"Jha","middleName":"","lastName":"Rajiv","suffix":""},{"id":475598429,"identity":"ca23fcf2-e1c7-40a5-a1d0-c7b0093a137d","order_by":2,"name":"Alfredo Conti","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIie3PMQrCMBSA4Rce1CXaNYv1CimCU/EsKUInBydxLBR00V1v0U3cLBm61HoAlxyhbgoqRlDBoenqkH9JMny8FwCb7R9rEQXgvB9iFgAg1TduIIj8Q0gsiuhDDOaHkLnU54sYxrgJOlU1DcBdrHKlnGO4bbUzBZNbLWEScbMuI2BFGcaCnsJd0hlx42LSldjW+3A29mPBTmEq6YCZSE9PwfuX8LKZ8BchXyL2zcTXhCzLiLKi8NdiP+qnUv9F8H4t8fIE4TINPHex5OfrY9hNj4dMVTev/vvv6O9TNAKbzWazmXoC2F5NTfMBFP8AAAAASUVORK5CYII=","orcid":"","institution":"Università di Bologna","correspondingAuthor":true,"prefix":"","firstName":"Alfredo","middleName":"","lastName":"Conti","suffix":""},{"id":475598430,"identity":"373ef8aa-7b81-4ef3-b6a0-a94c2648b727","order_by":3,"name":"Bipin Chaurasia","email":"","orcid":"","institution":"Neurosurgery Clinic","correspondingAuthor":false,"prefix":"","firstName":"Bipin","middleName":"","lastName":"Chaurasia","suffix":""}],"badges":[],"createdAt":"2025-04-03 18:38:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6371541/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6371541/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85617360,"identity":"17dc0c63-56fa-4ef5-9444-ae179cbd7859","added_by":"auto","created_at":"2025-06-29 14:45:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":571971,"visible":true,"origin":"","legend":"\u003cp\u003eBilateral MCA bifurcation aneurysms in a patient with subarachnoid hemorrhage (SAH).\u003c/p\u003e\n\u003cp\u003eThe ruptured aneurysm (right sided) was approached via the ipsilateral side. The contralateral aneurysm was deemed suitable for simultaneous clipping based on its size, morphological characteristics, MCA branching, and dome orientation. Postoperative CTA demonstrated complete obliteration of both aneurysms.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6371541/v1/ee3d49b7c3ea104b42cdef69.png"},{"id":85617355,"identity":"deb7ee7a-9c67-4743-ac5e-2ac884024109","added_by":"auto","created_at":"2025-06-29 14:45:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":488279,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6371541/v1/b1099db6204274764fd9ac83.jpg"},{"id":86363719,"identity":"037c9ace-ea42-4adb-8e00-a4aa66b5ccff","added_by":"auto","created_at":"2025-07-09 20:01:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2053056,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6371541/v1/bea1b9bf-aba4-40d2-87d1-c823ae77d1bd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Unilateral Approach to Bilateral Clipping of Intracranial Aneurysms: A Case Series","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIntracranial aneurysms are common vascular malformations presenting as multiple lesions in 7\u0026ndash;45% of cases. Bilateral aneurysms pose a unique challenge due to the need for multiple treatments involving bilateral craniotomies or combined endovascular and surgical treatments. As an alternative to this strategy, a single unilateral craniotomy for the clipping of both ipsilateral and contralateral aneurysms is possible [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], as a technique that reduces surgical burden while maintaining the efficacy of treatment [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe feasibility of this approach depends on various factors, including aneurysm size, location, and the degree of vascular tortuosity, always bearing the preferences and experience of the neurosurgeon in mind [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Meticulous preoperative planning by three-dimensional digital subtraction angiography (3D-DSA), allow a preoperative evaluation of the feasibility of this strategy increasing the safety and efficacy of the procedure.\u003c/p\u003e \u003cp\u003eThis study explores the clinical and surgical outcomes of a consecutive series of patients who underwent unilateral craniotomy for bilateral aneurysm clipping, with a focus on neurological outcomes, procedural challenges, and postoperative complications.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Cohort\u003c/h2\u003e \u003cp\u003eThis retrospective case series includes 10 patients treated at the National Neurosurgical Referral Center, National Academy of Medical Sciences, Nepal between March 2020 and April 2024. All patients were diagnosed with multiple intracranial aneurysms through a combination of clinical assessment and imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and digital subtraction angiography (DSA). \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eA second series of 10 patients undergoing bilateral surgical treatment was collected for comparison of radiological characteristics\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eVariables\u003c/h3\u003e\n\u003cp\u003ePatients were selected based on specific inclusion criteria, which required adequate preoperative imaging confirming the feasibility of the contralateral approach, a favorable surgical corridor, and the absence of significant brain swelling or midline shift. The severity of subarachnoid hemorrhage (SAH) was classified using the Hunt and Hess (HH) grading scale, while the modified Miller Fisher (MF) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] grading system was used to predict the risk of symptomatic vasospasm. Neurological outcomes were assessed using the modified Rankin Scale (mRS) before and after surgery.\u003c/p\u003e\n\u003ch3\u003eRadiological Characterization\u003c/h3\u003e\n\u003cp\u003eThe relevant radiographic images (computed tomographic angiography [CTA], magnetic resonance angiography, digital subtraction angiography) were retrieved from the hospital\u0026rsquo;s digital archiving system. For all patients, we (a) measured the maximal length, neck width, and size of the aneurysms and (b) evaluated the presence of calcifications, irregularities, complex anatomy and secondary pouches, shape (saccular vs fusiform), and the projection of the aneurysm dome in relation to the parent artery and sylvian fissure [\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eRadiological Evaluation of the Microsurgical Corridor\u003c/h3\u003e\n\u003cp\u003eWe measured the height in millimeters of each internal carotid artery (ICA) bifurcation above the planum sphenoidale, as well as the lengths of the contralateral anterior cerebral artery proximal segment (A1) and the middle cerebral artery proximal segment (M1). Additionally, the distance between both ICA bifurcations and their respective ipsilateral MCA aneurysms were recorded. We determined these distances via coronal CTA at the level of the ICA bifurcation and also compared them with 3-D CTA reconstruction models\u003c/p\u003e\n\u003ch3\u003eTreatment\u003c/h3\u003e\n\u003cp\u003eThe surgical procedure involved a pterional craniotomy on the non-dominant hemisphere or the side with the aneurysm being at higher risk of rupture. After dural opening, cerebrospinal fluid (CSF) drainage was performed to facilitate brain relaxation. Aneurysms were clipped in sequence, with ipsilateral aneurysms addressed first. The contralateral aneurysms were then accessed by retracting the frontal lobe and utilizing the interoptic, prechiasmatic, or trans-sylvian corridor for visualization and dissection. Postoperative angiography was performed in all patients to confirm complete aneurysm occlusion (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eOutcome\u003c/h2\u003e \u003cp\u003eThe outcome for both groups was assessed by a neurosurgeon at discharge and at 3 months follow-up. The outcome was classified according to the modified Rankin Scale (mRS) as good (mRS 0\u0026ndash;3) or poor (mRS 4\u0026ndash;6), based on the ability to walk without assistance.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEthics\u003c/h3\u003e\n\u003cp\u003e Informed consent was obtained from all participants in accordance with ethical guidelines. Given the retrospective nature of this study, ethical committee approval was waived, as permitted by local institutional review board regulations.\u003c/p\u003e \u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eClinical Characteristics of Patients\u003c/h2\u003e \u003cp\u003eThe study cohort consisted of ten patients, including eight females and two males, with a mean age of 51.2 years. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes demographic and clinical characteristics of patients. Nine patients had aneurysms located in the anterior circulation, while one had an aneurysm in the posterior circulation. Preoperative imaging revealed SAH in nine cases, with one patient presenting with SAH complicated by intracerebral hemorrhage (ICH).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEssential clinical characteristics of patients at presentation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresentation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eH\u0026amp;H\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMF\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u0026thinsp;+\u0026thinsp;ICH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSAH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eAbbr.: SAH: subarachnoid hemorrhage. ICH: intracerebral hemorrhage. HH\u0026ccedil; Hunt Hess. MF: Miller Fisher\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eNeurological grading using the Hunt and Hess scale indicated that six patients were classified as grade 2, three as grade 3, and one as grade 4 at the time of admission. Modified Miller Fisher grading demonstrated a predominance of grade 2 findings, suggesting a moderate risk of vasospasm. The timing of surgery ranged from two to seven days after ictus, with most procedures performed between the second- and fourth day following hemorrhage.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSize and Morphology of Aneurysms\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarizes the distribution of size, morphology, projections, and characteristics of the aneurysms. The median neck diameter of the ipsilateral aneurysm was 3.55 mm (range: 3\u0026ndash;5 mm) and the median size of the aneurysm dome was 6.1 mm (range: 5\u0026ndash;10 mm), whereas the median neck diameter of the contralateral aneurysm was 2.45 mm (range: 2\u0026ndash;3 mm) and the median length of then contralateral aneurysm dome was 4.8 mm (range: 4\u0026ndash;6 mm). All contralaterally approached aneurysms were unruptured.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of the distribution of size, morphology, projections, and characteristics of the aneurysms\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNeck size of ipsilateral aneurysm (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDome size of ipsilateral aneurysm (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eShape\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMargins\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eProjection\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNeck size of contralateral aneurysm (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDome size of contralateral aneurysm (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eShape\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eMargin\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eProjection\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003elobulated\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSuperior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eSuperolateral\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003elobulated\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnteroinferior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterosuperior\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRegular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePosterior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eSuperomedial\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRegular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eInferolateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eSuperomedial\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnterolateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterior\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnteroinferior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnteroinferior\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnterior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterolateral\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSuperior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterior\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIrregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAnteroinferior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterosuperior\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingle sac ruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eirregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSuperior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSingle sac unruptured\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eregular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eAnterolateral\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eRadiological Characteristics of Vessels Anatomy and Microsurgical Corridor\u003c/h2\u003e \u003cp\u003eMorphological characteristics of aneurysms were unilobar (80%), multilobar (20%). None presented calcifications or complex anatomy including direct branching from the aneurysm sac.\u003c/p\u003e \u003cp\u003eTo better understand characteristics of the surgical corridor for unilateral approach, we compared anatomical features including length of ipsilateral ICA, ipsi- and contralateral A1, contralateral M1 and distance of ipsilateral ICA bifurcation from the contralateral aneurysm and compared measures with those of a second population of patients, retrospectively selected, with bilateral aneurysm but undergoing bilateral surgical treatment. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes relevant data of all 20 patients.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of Aneurysm location and distribution of length of ipsilateral ICA, ipsi- and contralateral A1, contralateral M1 and distance of ipsilateral ICA bifurcation from the contralateral aneurysm in patients undergoing unilateral or bilateral approach\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eApproach\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIpsilateral aneurysm (ruptured)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eContralateral aneurysm (unruptured)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eICA length ipsilateral (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eA1 segment (ipsilateral/contralateral) (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eDistance from ipsilateral bifurcation to contralateral aneurysm (mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eACA (A2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12/10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA (M1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA-PCOM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Left\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eACOM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eACA (A2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Left\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8/7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8/7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Right\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7/7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Left\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA(M1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7/7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e10\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral Left\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eACOM, ICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11/9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e11\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft ICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight Pericallosal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e12\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft MCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e13\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ACA (A2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft MCA (M3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e14\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ICA-PCom\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft MCA (M3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10/12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e15\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ACA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft ACA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17/15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e16\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft A2-A3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14/15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e17\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight MCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft ACA (A4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15/15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e18\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight choroidal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft M2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13/14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e19\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft supracallosal (A4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight MCA (M3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6/5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e20\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight ICA-PCom\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft ACA (A2-A3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e summarizes the median and interquartile range (IQR) for each surgical corridor variable by surgical approach. Median length of the ICA was 25.5mm; IQ 3.5 in the unilateral craniotomy group and 22.5mm, IQR 2.5mm, in the bilateral craniotomy group. Median length of the ipsilateral A1 was 10mm, IQR 2, in the unilateral craniotomy group and 13.5mm, IQR 4.75mm, in the bilateral craniotomy group. Median length of the contralateral A1 was 8mm, IQ 1.75, in the unilateral craniotomy group and 13mm, IQ 2.75mm, in the bilateral craniotomy group. The median distance of the contralateral aneurysm from the ipsilateral ICA bifurcation was 33mm, IQR 3.75mm, in the unilateral craniotomy group and 50.5mm, IQR 7mm, in the bilateral craniotomy group (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMedian and interquartile range (IQR) for each surgical corridor variable by surgical approach.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eApproach\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eIQR\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eICA Length\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eICA Length\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eA1 Segment (Ipsilateral)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eA1 Segment (Ipsilateral)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eA1 Segment (Contralateral)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eA1 Segment (Contralateral)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDistance to Contralateral Aneurysm\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e59.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDistance to Contralateral Aneurysm\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBilateral craniotomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSurgical approach and patient\u0026rsquo;s outcome\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIctal day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eApproach\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIpsilateral aneurysm (ruptured)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eContralateral aneurysm (unruptured)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSymptomatic Vasospasm(yes/no)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eHospital stay\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eOutcome\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eACA (A2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA (M1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA-PCOM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eACOM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eACA (A2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMCA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMCA(M1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLeft\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eACOM, ICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eICA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePoor\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe statistical analysis showed no significant difference of ICA length in the two groups (P\u0026thinsp;=\u0026thinsp;0.08). On the other hand, ipsilateral A1 length was shorter in the unilateral group (P\u0026thinsp;=\u0026thinsp;0.03), so well as the contralateral A1 length (P\u0026thinsp;=\u0026thinsp;0.002), and the distance between the ipsilateral ICA to contralateral aneurysm (P\u0026thinsp;=\u0026thinsp;0.002) (Table \u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMann-Whitney U tests were used to compare distributions between the two surgical approaches\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eU Statistic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP-Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eICA Length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e73.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0869\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1 Segment (Ipsilateral)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e22.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0334\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1 Segment (Contralateral)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0026\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance to Contralateral Aneurysm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eTreatment and Outcome\u003c/h2\u003e \u003cp\u003eAll patients underwent successful clipping of ipsi- and contralateral aneurysms. Postoperative angiography confirmed complete occlusion in all cases. One patient experienced a mild intraoperative ipsilateral aneurysm rupture, which was promptly managed with temporary clipping and controlled hypotension. Severe vasospasm was observed in one patient postoperatively, leading to mortality on the third postoperative day despite aggressive medical management. The remaining nine patients demonstrated favorable neurological recovery, with an improvement in mRS scores at follow-up (table 6). The mean hospital stay was 9.6 days, reflecting a relatively expedited recovery process compared to traditional bilateral craniotomy approaches.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe management of multiple intracranial aneurysms remains a subject of debate, with surgical clipping and endovascular coiling being the two primary treatment modalities. While endovascular coiling offers a minimally invasive alternative, it is often limited by anatomical constraints, particularly in cases of wide-necked aneurysms or those with complex branching patterns. Microsurgical clipping, on the other hand, provides definitive aneurysm occlusion and remains the preferred approach in most patients with ruptured aneurysms. In general, it is widely accepted to clip all accessible aneurysms through a single approach [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Nonetheless, the optimal strategy depends on the clinical condition of the patient, radiological parameters of the aneurysms and the microsurgical corridors, resources and previous experience of the surgeon and overall Institution.\u003c/p\u003e \u003cp\u003eA unilateral approach to bilateral aneurysm clipping offers several advantages, including the elimination of a second craniotomy, reduced operative morbidity, and shorter hospitalization. All aneurysms treated through a contralateral approach in our series were unruptured, in concordance with previous literature underscoring that ruptured aneurysms should be approached from the ipsilateral side [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. All aneurysms treated in this series were smaller than 15 mm. According to previous authors, the size of the aneurysm for safe contralateral clipping should be less than 15 mm [\u003cspan additionalcitationids=\"CR9 CR10 CR11\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Complex aneurysms including multilobar, calcified, those for which direct branching from the sac is suspected, as well as those for which a difficult dissection is predictable should be treated by ipsilateral approach [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Furthermore, a contralateral microsurgical approach should not be attended in patients presenting with severe SAH, tight brain, and edema; avoiding the risk to produce additional injuries to the surrounding neurovascular structures because of excessive brain retraction and difficult dissection. Adequate brain relaxation is critical for safe contralateral exposure, and this was achieved through CSF drainage, mannitol administration, and controlled anesthesia to optimize brain compliance.\u003c/p\u003e \u003cp\u003eThe choice of surgical corridor depends on the location of the contralateral aneurysm. The distance of dissection and the size of the contralateral surgical corridor depend on the length of both A1 and contralateral M1 segments. In our series of contralaterally approached aneurysms, the median A1 length of 14.22 mm (range: 12-16.1 mm) and M1 length of 14.97 mm (range: 12.2\u0026ndash;17 mm) agreed with previous anatomic and radiological findings. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The median distance of the contralateral aneurysm from the ipsilateral ICA bifurcation was 33mm, IQR 3.75mm. When compared with patients undergoing bilateral craniotomy, this distance was 50.5mm, IQR 7mm (P\u0026thinsp;=\u0026thinsp;0.002) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Our results suggest that we can consider 30\u0026ndash;35 mm reasonable for attempting bilateral clipping. Nonetheless, independently from those measures, an M1 and MCA bifurcation aneurysm neck may remain only approximately 1.5 cm and 3 cm away from the anterior communicating artery, as the approach is from more anterior than lateral, and the absolute distance can be possibly less than the sum of the lengths of A1 and M1, making preoperative measurements not necessarily an absolute indication not to attempt bilateral clipping. Understandably, a greater work and attention in opening sylvian fissures is required, because this needs to be more extensive and distal. As a narrative notice, we perceived that a contralateral MCA trunk directing downward increased the feasibility to expose the aneurysm while more distally placed MCA bifurcations are curved around the insula making their exposure difficult because a direct line of sight is lost for distally placed bifurcations.\u003c/p\u003e \u003cp\u003eOne of the disadvantages of the contralateral approach is the need of frontal lobe retraction. Nevertheless, it should be noted that olfactory dysfunction is recorded in 58% in ipsilateral pterional craniotomy, suggesting a high risk of anosmia in bilateral approaches [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The internal carotid artery (ICA) bifurcation represents the highest point of the circle of Willis (Fig.\u0026nbsp;2), and its height may be related to the need of frontal lobe retraction for aneurysms beyond the contralateral ICA bifurcation. In our series, a median height of the ICA bifurcation of 50.72 mm (range: 35.8\u0026ndash;63 mm) allowed a safe approach without excessive frontal lobe retraction.\u003c/p\u003e \u003cp\u003eDespite the technical complexity, the overall complication rate in this study was low. One case of intraoperative rupture was successfully managed, and only one patient succumbed to vasospasm-related complications. These findings align with previous reports suggesting that unilateral clipping can be performed safely in appropriately selected cases. Altogether, the abovementioned parameters serve as a guide for the preoperative selection of the contralateral approach for bilateral aneurysms and to support a policy to perform a unilateral approach from the first attempt provided that the surgical team has extensive experience in microsurgical techniques.\u003c/p\u003e \u003cp\u003eThe limitations of this study include its small sample size and retrospective design, which may limit the generalizability of the findings. Additionally, long-term follow-up was not included in the present analysis, making it difficult to assess the potential for aneurysm recurrence or delayed complications. Future studies with larger patient cohorts and prospective designs will be essential to further validate the safety and efficacy of this approach.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eA unilateral craniotomy for bilateral aneurysm clipping is a viable and effective alternative to traditional staged surgeries, offering reduced morbidity and hospital stay. This technique requires careful patient selection, precise preoperative planning, and advanced microsurgical skills to ensure favorable outcomes. While the approach is not universally applicable, it represents a valuable addition to the armamentarium of neurosurgeons managing complex aneurysm cases. Further research and long-term follow-up studies are warranted to establish its broader applicability and refine surgical strategies.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all participants. This consent included consent to participate any clinical retrospective study and consent to publish results. Given the retrospective nature of this study, ethical committee approval was waived, as permitted by local institutional review board regulations (National Academy of Medical Sciences of Kathmandu [NAMSK] Ethical Committee).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eClinical data public use is restricted\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e: This research was funded by Next Generation EU \u0026ndash; PNRR M6C2, project number: PNRR-TR1-2023-12377246\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent Statement:\u003c/strong\u003e Written informed consent has been obtained from the patient to publish this paper\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest:\u003c/strong\u003e The authors declare no conflicts of interest\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBishnoi I (2021) Contralateral Aneurysm Clipping. In: Kato Y, Zhang X, Dai J, Ansari A (eds) Recent Progress in the Management of Cerebrovascular Diseases. Springer, Singapore. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/978-981-16-3387-4_11\u003c/span\u003e\u003cspan address=\"10.1007/978-981-16-3387-4_11\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMuirhead WR, Layard Horsfall H, Khan DZ, Koh C, Grover PJ, Toma AK, Castanho P, Stoyanov D, Marcus HJ, Murphy M (2022) Microsurgery for intracranial aneurysms: A qualitative survey on technical challenges and technological solutions. Front Surg 9:957450. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fsurg.2022.957450\u003c/span\u003e\u003cspan address=\"10.3389/fsurg.2022.957450\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003ePMID: 35990100; PMCID: PMC9386123\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePanigrahi M, Patel C, Koradia P, Chandrasekhar YBVK (2022) Contralateral Clipping of Multiple Intracranial Aneurysms. Adv Tech Stand Neurosurg. ;44:161\u0026ndash;173. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/978-3-030-87649-4_8\u003c/span\u003e\u003cspan address=\"10.1007/978-3-030-87649-4_8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. PMID: 35107678\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArrese I, Sarabia R (2012) Contralateral approach for middle cerebral artery aneurysms with long M1 segment: report of 2 cases. Neurocirugia (Astur) 23(3):122\u0026ndash;126. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.neucir.2012.02.001\u003c/span\u003e\u003cspan address=\"10.1016/j.neucir.2012.02.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003eEpub 2012 May 2. PMID: 22561020\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDashti R, Hernesniemi J, Niemela M et al (2007) Microneurosurgical management of middle cerebral artery bifurcation aneurysms. Surg Neurol 67(5):441\u0026ndash;456\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDashti R, Rinne J, Hernesniemi J et al (2007) Microneurosurgical management of proximal middle cerebral artery aneurysms. Surg Neurol 67(1):6\u0026ndash;14\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eElsharkawy A, Lehecka M, Niemela M et al (2013) A new, more accurate classification of middle cerebral artery aneurysms: computed tomography angiographic study of 1,009 consecutive cases with 1,309 middle cerebral artery aneurysms. Neurosurgery 73(1):94\u0026ndash;102 discussion 102\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRodriguez-Hernandez A, Gabarr\u0026oacute;s A, Lawton MT (2012) Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique. Neurosurgery 71(1 suppl operative):116\u0026ndash;123 discussion 123\u0026ndash;124\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcMahon JH, Morgan MK, Dexter MA (2001) The surgical management of contralateral anterior circulation intracranial aneurysms. J Clin Neurosci 8(4):319\u0026ndash;324\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eInci S, Akbay A, Ozgen T (2012) Bilateral middle cerebral artery aneurysms: a comparative study of unilateral and bilateral approaches. Neurosurg Rev 35(4):505\u0026ndash;517 discussion 517\u0026ndash;518\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Oliveira E, Tedeschi H, Siqueira MG et al (1996) Anatomical and technical aspects of the contralateral approach for multiple aneurysms. Acta Neurochir (Wien) 138(1):1\u0026ndash;11 discussion 11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Sousa AA, Filho MA, Faglioni W Jr, Carvalho GT (2005) Unilateral pterional approach to bilateral aneurysms of the middle cerebral artery. Surg Neurol 63(suppl 1):S1\u0026ndash;S7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndrade-Barazarte H, Kivelev J, Goehre F, Jahromi BR, Noda K, Ibrahim TF, Kivisaari R, Lehto H, Niemela M, J\u0026auml;\u0026auml;skel\u0026auml;inen JE, Hernesniemi JA (2015) Contralateral Approach to Bilateral Middle Cerebral Artery Aneurysms: Comparative Study, Angiographic Analysis, and Surgical Results. Neurosurgery. ;77(6):916\u0026thinsp;\u0026ndash;\u0026thinsp;26; discussion 926. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1227/NEU.0000000000000930\u003c/span\u003e\u003cspan address=\"10.1227/NEU.0000000000000930\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. PMID: 26308631\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRodriguez-Hernandez A, Gabarr\u0026oacute;s A, Lawton MT (2012) Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique. Neurosurgery 71(1 suppl operative):116\u0026ndash;123 discussion 123\u0026ndash;124\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eInci S, Akbay A, Ozgen T (2012) Bilateral middle cerebral artery aneurysms: a comparative study of unilateral and bilateral approaches. Neurosurg Rev 35(4):505\u0026ndash;517 discussion 517\u0026ndash;518\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOshiro EM, Rini DA, Tamargo RJ (1997) Contralateral approaches to bilateral cerebral aneurysms: a microsurgical anatomical study. J Neurosurg 87(2):163\u0026ndash;169\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRhoton AL Jr (2002) The supratentorial arteries. Neurosurgery 51(4 suppl):S53\u0026ndash;S120\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCho et al (2017) Comparison of Unilateral and Bilateral Craniotomy for the Treatment of Bilateral Middle Cerebral Artery Aneurysms: Anatomic and Clinical Parameters and Surgical Outcomes. World Neurosurg 108:627\u0026ndash;635\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"cerebral aneurysm, approach, microsurgery, clipping, outcome","lastPublishedDoi":"10.21203/rs.3.rs-6371541/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6371541/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMultiple intra-cranial aneurysms whose incidence ranges 7\u0026ndash;45% pose significant management issues, often due to the necessity of multiple sequential treatments. We present a consecutive series of patients undergoing unilateral surgical approach to clipping of bilateral intracranial aneurysms and their peri-operative outcome.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis is a retrospective case series of ten patients who presented to the National neurosurgical referral center, National academy medical sciences, Nepal between March 2020 and April 2024 with multiple aneurysms. The patients were evaluated and diagnosed based on clinical judgement as well as using CT/MR/DS angiography as imaging modality. Patients admitted with diagnosis of multiple aneurysms, who underwent unilateral approach to bilateral clipping of aneurysms, were included in the study.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003e10 patients underwent unilateral approach to bilateral clipping of intracranial aneurysms. Nine aneurysms were clipped without intra-operative complications, one had mild intra-operative rupture of the ipsilateral aneurysm. The post-operative CT angiography showed obliteration of ipsi- and contralateral aneurysms with no additional morbidity due to prolonged and more extensive dissection. Morphological parameters used to evaluate feasibility of bilateral clipping included limited length of the contralateral A1-M1, size and morphology of the aneurysms, tightness of the subarachnoid space due to hemorrhagic adhesion.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eContralateral approach is an effective technique to treat bilateral aneurysms with a single surgery, being cost-effective with a reasonable risk profile, provided that a correct preoperative planning is done.\u003c/p\u003e","manuscriptTitle":"Unilateral Approach to Bilateral Clipping of Intracranial Aneurysms: A Case Series","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-29 14:45:14","doi":"10.21203/rs.3.rs-6371541/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c1e9e5dc-6b35-4ce3-8bcb-2debd2d69c6a","owner":[],"postedDate":"June 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-09T19:53:34+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-29 14:45:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6371541","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6371541","identity":"rs-6371541","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}