Mechanical thrombectomy for acute ischemic stroke with absent opacification of the cervical internal carotid artery at CT-angiography: pathophysiology and outcome

Mechanical thrombectomy for acute ischemic stroke with absent opacification of the cervical internal carotid artery at CT-angiography: pathophysiology and outcome | 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 Help Center Sign In Submit a Preprint Cite Share Download PDF Article Mechanical thrombectomy for acute ischemic stroke with absent opacification of the cervical internal carotid artery at CT-angiography: pathophysiology and outcome Alessio Comai, Chiara Casalboni, Matteo Bonatti, Enrica Franchini, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4307068/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 Purpose Occlusion of distal internal carotid artery can simulate a proximal occlusion of its cervical tract at CT angiography in patients with acute ischemic stroke, i.e. pseudo-occlusion. As true and false carotid occlusions can have similar presentation at non-invasive imaging of a patient undergoing endovascular treatment for stroke, our study aimed to evaluate clinical and technical differences of these conditions and the possible consequences of a misdiagnosis. Methods We retrospectively reviewed consecutive patients who underwent mechanical thrombectomy for acute ischemic stroke in a single center between July 2015 and July 2021 and included patients with absent opacification of cervical carotid artery at CT-angiography. Digital subtraction angiography (DSA) imaging and procedural data were evaluated to define the actual localization of occlusion. We compared imaging and clinical data of patients with true and false carotid occlusion, including collateral circulation at CTA, revascularization grade and clinical outcome at 3 months. Results 95 patients were included, 52 (49%) had true occlusion of cervical internal carotid artery. Compared to the pseudo-occlusion group, collateral circulation at CTA was moderate to good in 67% of cases (vs 29%; p < 0.01) and mean ASPECT score at 24h was 5.5 vs 2.7 (p < 0.001). Modified Rankin scale 0–2 at 90 days was more frequent in patients with true occlusion compared to patients with pseudo-occlusion (44.9 vs 14.6%; p 0.003). Conclusion Pseudo-occlusion of cervical internal carotid artery in patients with acute ischemic stroke seem to be associated with worst prognosis and poorer collateral circulation. Health sciences/Anatomy/Nervous system/Brain Biological sciences/Neuroscience Health sciences/Neurology Acute ischemic stroke Endovascular treatment Mechanical thrombectomy Collateral circulation CT angiography Stroke imaging Introduction Non-invasive neuroimaging modalities can lead to diagnostic misinterpretation in acute occlusion of internal carotid artery (ICA) of patients presenting with acute ischemic stroke [ 1 , 2 ]. Distal ICA occlusion can simulate a more proximal occlusion at cervical level, a condition known as pseudo-occlusion [ 3 ]. CT angiography is the most available method to identify occlusion of intracranial large arteries and to evaluate collateral circulation in patients with acute ischemic stroke [ 4 , 5 ]. Endovascular mechanical thrombectomy (MT) together with or without systemic thrombolysis has been proven effective by several randomized controlled trials in reducing morbidity and mortality of patients with acute ischemic stroke due to intracranial large-vessel occlusion in comparison with systemic thrombolysis alone [ 6 ]. Current indications for mechanical thrombectomy include occlusion of large intracranial vessels, including ICA, M1 and proximal M2, and tandem occlusions, i.e. association of extracranial ICA occlusion and downstream intracranial large vessel occlusion [ 7 , 8 ]. These two conditions can present with at least partially overlapping features at non-invasive vascular imaging, namely with absent opacification of the cervical tract of ICA. Despite similar clinical and imaging presentation, these two conditions underly completely different etiologies: proximal true occlusions of ICA are mostly atheromatic or dissective, whereas distal occlusions are more frequently embolic [ 9 ]. Acute ICA occlusion is associated with poor clinical outcomes [ 10 ]. Nevertheless, patients with acute ICA occlusion can present ranging from asymptomatic to affected by acute severe stroke symptoms, depending on occlusion pattern, hemodynamic impairment and collateral circulation [ 11 ]. Our study aimed to compare these conditions in terms of technical and clinical outcomes in patients who are candidates for mechanical thrombectomy. Methods Study design We retrospectively reviewed consecutive patients who underwent mechanical thrombectomy for acute ischemic stroke between July 2015 and July 2021 at a single third-level stroke center (Fig. 1 ). The study was approved by the Ethical Committee of Azienda Sanitaria della Provincia Autonoma di Bolzano, which waived patients’ informed consent for retrospective data collection, and was performed in accordance with Declaration of Helsinki. Selection criteria We included all consecutive patients with absent opacification of cervical ICA at CT-angiography except a short proximal segment of 2 cm. Digital subtraction angiography (DSA) imaging and procedural data were used as gold standard to define the actual localization of occlusion and hence the mechanism for absent ICA opacification. Pseudo-occlusion was defined as non opacification at CTA simulating a proximal occlusion and patency at prolonged DSA run or at catheter exploration with actual distal occlusion, as suggested by Grossberg JA et at [ 3 ]. Patients with a partial opacification of the cervical ICA at CTA or with a contrast gradient along the vessel were excluded as the diagnosis of false occlusion is obvious. We collected demographic, clinical and imaging data, including age, sex, baseline Nation Institute of Health Stroke Scale (NIHSS) score, intravenous administration of recombinant tissue plasminogen activator (rtPA), Alberta Stroke Program Early CT (ASPECT) score at presentation and after 24 hours, modified Thrombolysis in Cerebral Infarction (mTICI) score, any intraparenchymal hemorrhage at 24 hours CT, modified Rankin Score (mRS) after 3 months. Technique and protocols All CT imaging was obtained on a 2 × 64 detector rows Dual Source scanner. Non-contrast CT was acquired using the axial technique with 120 kVp, 100–350 auto-mAs, and 5-mm section thickness reconstructions. CTA was acquired using triple phase technique after 60 mL of 350 mgI/ml iodinated contrast medium injection at a 4 mL/s flow rate. The first phase, from aortic root to the vertex, was acquired using bolus tracking technique with 5 seconds delay after a 100 HU threshold was reached in the aortic arch, whereas the second and the third phases, limited to the intracranial circle, were acquired with a 8 second fix delay from the previous ones. In case of unknown stroke onset time or beyond 6 hours from onset time, CT perfusion was used to select patients according to DAWN and DEFUSE-3 randomized clinical trials criteria followed by a single-phase CTA from aortic arch to the intracranial circulation [ 7 ]. Endovascular treatment Endovascular procedures were performed on a biplane X-ray system by 1 out of 4 radiologists with 5 to 15 years of experience in stroke interventions. All patients underwent a preliminary angiographic examination to confirm and precisely localize the occlusion and to guide the subsequent treatment. Pseudo-occlusion was diagnosed by documenting sluggish, slow and pulsatile progressions of contrast into the ICA. In those cases, a diagnostic 5F catheter or a large-bore aspiration catheter was advanced to look for a terminal occlusion. Image analysis Qualitative image analysis was performed by two neuroradiologists, with 13 and 10 years of experience in stroke imaging and treatment, unaware of patients’ clinical data, on a dedicated workstation using commercially available software (Syngo.via Version VB30, Siemens, Erlangen, Germany). They were asked to assess ASPECTS (0–10) on unenhanced brain CT, baseline and at 24 hours, and collateral score (good/intermediate/poor collaterals) on CTA, according to the classification by Tan et al [ 5 ]. Discrepancies were solved by consensus. Post-procedural DSA imaging was also evaluated to determine revascularization according to the mTICI score. Statistical analysis Data are reported as means with standard deviations or medians for continuous variables. Continuous variables were compared with independent-samples two-tailed t-test, dichotomous variables with Fisher’s exact test. p-value inferior to 0.05 was considered statistically significant. Results On a total of 493 endovascular stroke procedures, 95 consecutive patients with absent opacification of ICA at baseline CTA were included. 52 (55%) had true occlusion of cervical ICA associated to a large intracranial vessel occlusion (41 atheromatic, 7 dissected, 4 embolic), 43 (45%) had distal ICA occlusion presenting as pseudo-occlusion (PO), the latter being all embolic. Baseline NIHSS, ASPECT score in admission, and intravenous administration of rtPA did not significantly differ between the two groups. Compared to the PO group, collateral circulation at CTA was moderate to good in 67% of cases (vs 29%; p < 0.01) and mean infarction volume measured as ASPECT score at 24h control CT was lower: 2.7 vs 5.5 (p < 0.001). Good outcome after 3 months, defined as modified Rankin Score 0–2, was more likely in patients with tandem occlusion (TO) compared to patients with pseudo-occlusion (44.9 vs 14.6%; p 0.003). Notably, there was no significant difference in terms of revascularization (75% in TO vs 67.4% in PO) or intracranial parenchymal hemorrhage at 24h CT (Table 1 ). Mortality was almost double in PO group but not statistically significant. Table 1 SD = standard deviation; av = average; CS = collateral score according Tan IYL et al [ 5 ]; TICI = thrombolysis in cerebral infarction; ASPECT = Alberta stroke program early CT; IPH = intracranial parenchymal hemorrhage; SAH = subarachnoid hemorrhage; mRS = modified Rankin Scale. True occlusion Pseudo-occlusion P value (test) n 52 43 BASELINE Sex, male (%) 35 (67.3) 32 (74.4) ≥ 0.05 Age, years av (SD) 64 (14) 73 (12) ≥ 0.05 Age, years min-max 30–88 43–91 ≥ 0.05 NIHSS on admission, av 18 (n = 38) 21 (n = 36) ≥ 0.05 ASPECT, av 8 (n = 51) 7 ≥ 0.05 CS score, av 2.0 (n = 51) 1.0 p = 0.0155 (Chi-square) CS score 2–3 (%) 33/49 (67) 12/41 (29) p = 0.0006 (Fisher’s exact) Etiology (%) Atheromatous 41 (79) Dissective 7 (13.5) Embolic 4 (7.5) Embolic 43 (100) p = 0.00001 (Fisher’s exact) INTERVENTION Intravenous rt-PA (%) 29/40 (72.5) 19/31 (61) ≥ 0.05 TICI score 2B-3 (%) 39/52 (75) 29/43 (67.4) ≥ 0.05 OUTCOME ASPECT after 24 h, av 5.5 (n = 50) 2.7 (n = 42) p = 0.0004 (Mann-Whitney's) ASPECT 6–10 after 24 h (%) 31/50 (62) 9/42 (21.4) p = 0.0001 (Fisher’s exact) IPH after 24h (%) 7/52 (13.5) 9/43 (20.9) ≥ 0.05 SAH after 24h (%) 4/52 (7.7) 7/43 (16.3) ≥ 0.05 mRS 0–2 at 90 days (%) 22/49 (44.9) 6/41 (14.6) p = 0.0027 (Fisher’s exact) mRS 0–2/surv at 90 days (%) 22/38 (57.9) 6/24 (25) p = 0.0179 (Fisher’s exact) Mortality at 90 days (%) 11/49 (22.4) 17/41 (41.5) ≥ 0.05 Discussion Mechanical thrombectomy dramatically changed the outcome of patients with acute ischemic stroke due to anterior circulation intracranial large vessel occlusion. Randomized clinical trials included patients with terminal ICA occlusion and M1 tract of middle cerebral artery, also with concomitant cervical tract ICA occlusion or severe stenosis (tandem lesions) [ 6 ]. Prespecified subgroup analysis found a higher treatment effect for patients with stroke due to ICA occlusion in comparison with more distal locations (common Odds Ratio 3.96) as well as for patients with tandem lesions (cOR 2.95) [ 6 ], but ICA occlusion has also been reported as negative prognostic factor [ 12 , 13 ]. Terminal carotid occlusion and tandem occlusions were also associated to higher complication rate during mechanical thrombectomy in the French ETIS registry, being predictors of embolus to new territory [ 14 ]. Similarly, the Italian Registry of Endovascular Stroke Treatment reported higher risk of subarachnoid hemorrhage/arterial perforation rate and higher risk of developing symptomatic intracranial hemorrhage in patients treated for distal intracranial carotid occlusion [ 15 ]. ICA occlusions encompass different clinical conditions and can be misinterpreted [ 1 – 3 ]. ICA can be involved in many different ways in patients undergoing endovascular treatment for acute ischemic stroke: distal occlusion involving the apical tract are usually embolic and frequently caused by the migration of massive thrombi originating from cardiac chambers due to atrial fibrillation, whereas proximal occlusions ae usually atheromatous or due to dissection [ 9 ]. Isolated apex occlusions show different presentations at CT-angiography according to the opacification of the upstream cervical tract, due to presence or absence of outflow vessels: if outflow arteries as the ophtalmic or the posterior communicating branches are absent, there is no progression of contrast medium into the vessel simulating a proximal ICA occlusion (pseudo-occlusion). If outflow vessels are thin with a limited downstream capacity, there can be a slow progression of contrast media that can be documented as a contrast gradient along the ICA or a late opacification at multiphase CTA [ 16 , 17 ]. Although morphology of occlusion at CTA and multiphase CTA have been suggested to improve diagnostic accuracy, pseudo-occlusions remain a significant issue with angiographic microcatheter exploration being often required for the proper diagnosis [ 3 , 18 – 20 ]. In this study, we decided to adopt a very strict definition of pseudo-occlusion, excluding patients with a contrast gradient along ICA which makes differential diagnosis more obvious, and we did not consider later phase acquisition. As suggested by multiple studies, pseudo-occlusion is a particularly unfavorable presentation of acute ischemic stroke in patients treated both with intravenous thrombolysis and mechanical thrombectomy [ 21 – 24 ]. These authors constantly reported lower revascularization rate in patients with pseudo-occlusions after endovascular treatment, in contrast with our experience. We reported unfavorable outcome for patients with pseudo-occlusions without a significant difference in terms of reperfusion rates. Our technical approach was not different to treat the two conditions in the study period: aspiration first and stentretriever-assisted thrombectomy only if necessary, and in tandem occlusion intracranial first treatment and carotid stenting only in limited selected cases. Collateral status is a well-known prognostic factor in patients undergoing endovascular treatment for acute ischemic stroke [ 25 – 27 ]. For example, composition of Willis circle can determine different outcomes in patients with distal ICA occlusion [ 28 ]. Poor collateral circulation is a possible explanation for the unfavorable outcome for patients with pseudo-occlusion, the latter being associated with slow or absent flow through the ICA [ 21 ]. Multiphase CTA seems to be superior to single-phase CTA to evaluate collateral circulation, but due to radiation dose exposure it should be used in alternative to CT perfusion [ 29 , 30 ]. MCTA could also help to identify pseudo-occlusion [ 20 ], but this only applies to slow-flow cases and not to cases with completely absent inflow [ 3 ]. Our study found a relevant difference in terms of clinical outcome and collateral circulation evaluated at single-phase CT-angiography, which was available both in patients who underwent CT perfusion (beyond 6 hours from stroke onset time and unknown onset time) and multiphase CT angiography (within 6 hours from stroke onset time). Interestingly this observation, if confirmed by larger studies, could be widely adopted on the basis of a fast and easy examination. Our study is firstly limited by its retrospective design. Secondly, we adopted a stricter definition of pseudo-occlusions than usual. Moreover, it reports data from a single stroke center and images were not evaluated by an independent core laboratory. A larger multicenter study is needed to confirm our results. Conclusions Pseudo-occlusion of cervical internal carotid artery in patients with acute ischemic stroke is likely to be associated with worst prognosis and poorer collateral circulation. This imaging feature could represent an additional variable to consider when selecting stroke patients for endovascular treatment. Declarations Competing interest On behalf of all authors, the corresponding author states that there is no conflict of interest. Author Contribution AC and CC designed the study and wrote the main manuscript. MB, EF and EDO helped to collect and elaborate data. GNG and FL contributed to statistical analysis and data interpretation. BP has drafted the manuscript. All authors reviewed the manuscript. Data Availability The datasets used and analysed during the current study are available from the corresponding author on reasonable request. References Kappelhof M, Marquering HA, Berkhemer OA, et al. 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Also discoverable on Platform About In Review Editorial Policies 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-4307068","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":297007271,"identity":"5ee394e0-6b26-4eab-9f0f-42716075cd51","order_by":0,"name":"Alessio Comai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIiWNgGAWjYDACdhBhAOUkVEDZCfi0MKNoOQPTgk8PMzKHsQ2mHY8W/mbmwx9/FNgw8Ld3J354OK9O3py9/QHDwx+4tUgcZkuT5jFIY5A4c3azROK2w4Y7e84Y4HfYYR4zZgaDwwwGErkbgFoOMG64kYPfL/KH+T9//AHRsvlH4pw6+w33nz/Aq8XgMA+DBA9EyzaJxAbmxA03GPA7zPAwmxnILzxAv2yzSDh2OHlnT47BgYQ03Frkjjc//vjjj40cf3vv5ps/aupst7Mff/jwhw0e70MBDwrvAGENo2AUjIJRMArwAQAPY1DSXqGUSwAAAABJRU5ErkJggg==","orcid":"","institution":"Neuroradiology, Hospital of Bolzano (SABES-ASDAA), Teaching Hospital of Paracelsius Medical University (PMU), Bolzano-Bozen, Italy; 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viale Rizzardi 4, Negrar (VR), Italy","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Fabio","middleName":"","lastName":"Lombardo","suffix":""},{"id":297007291,"identity":"f9edcf8d-2ded-4244-9d3e-eea5975ddbc1","order_by":7,"name":"Benedetto Petralia","email":"","orcid":"","institution":"Azienda Ospedaliera Universitaria Integrata Verona","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Benedetto","middleName":"","lastName":"Petralia","suffix":""}],"badges":[],"createdAt":"2024-04-22 15:56:58","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4307068/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4307068/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62577385,"identity":"f8985a90-0a84-462f-9072-0551745a610f","added_by":"auto","created_at":"2024-08-16 05:29:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":507659,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4307068/v1/7f4dfd8b-8d70-407a-a9d9-9526757d5b91.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Mechanical thrombectomy for acute ischemic stroke with absent opacification of the cervical internal carotid artery at CT-angiography: pathophysiology and outcome","fulltext":[{"header":"Introduction","content":"\u003cp\u003eNon-invasive neuroimaging modalities can lead to diagnostic misinterpretation in acute occlusion of internal carotid artery (ICA) of patients presenting with acute ischemic stroke [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Distal ICA occlusion can simulate a more proximal occlusion at cervical level, a condition known as pseudo-occlusion [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. CT angiography is the most available method to identify occlusion of intracranial large arteries and to evaluate collateral circulation in patients with acute ischemic stroke [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEndovascular mechanical thrombectomy (MT) together with or without systemic thrombolysis has been proven effective by several randomized controlled trials in reducing morbidity and mortality of patients with acute ischemic stroke due to intracranial large-vessel occlusion in comparison with systemic thrombolysis alone [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Current indications for mechanical thrombectomy include occlusion of large intracranial vessels, including ICA, M1 and proximal M2, and tandem occlusions, i.e. association of extracranial ICA occlusion and downstream intracranial large vessel occlusion [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. These two conditions can present with at least partially overlapping features at non-invasive vascular imaging, namely with absent opacification of the cervical tract of ICA. Despite similar clinical and imaging presentation, these two conditions underly completely different etiologies: proximal true occlusions of ICA are mostly atheromatic or dissective, whereas distal occlusions are more frequently embolic [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Acute ICA occlusion is associated with poor clinical outcomes [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Nevertheless, patients with acute ICA occlusion can present ranging from asymptomatic to affected by acute severe stroke symptoms, depending on occlusion pattern, hemodynamic impairment and collateral circulation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Our study aimed to compare these conditions in terms of technical and clinical outcomes in patients who are candidates for mechanical thrombectomy.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eWe retrospectively reviewed consecutive patients who underwent mechanical thrombectomy for acute ischemic stroke between July 2015 and July 2021 at a single third-level stroke center (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The study was approved by the Ethical Committee of Azienda Sanitaria della Provincia Autonoma di Bolzano, which waived patients\u0026rsquo; informed consent for retrospective data collection, and was performed in accordance with Declaration of Helsinki.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eSelection criteria\u003c/h2\u003e \u003cp\u003eWe included all consecutive patients with absent opacification of cervical ICA at CT-angiography except a short proximal segment of 2 cm. Digital subtraction angiography (DSA) imaging and procedural data were used as gold standard to define the actual localization of occlusion and hence the mechanism for absent ICA opacification. Pseudo-occlusion was defined as non opacification at CTA simulating a proximal occlusion and patency at prolonged DSA run or at catheter exploration with actual distal occlusion, as suggested by Grossberg JA et at [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Patients with a partial opacification of the cervical ICA at CTA or with a contrast gradient along the vessel were excluded as the diagnosis of false occlusion is obvious. We collected demographic, clinical and imaging data, including age, sex, baseline Nation Institute of Health Stroke Scale (NIHSS) score, intravenous administration of recombinant tissue plasminogen activator (rtPA), Alberta Stroke Program Early CT (ASPECT) score at presentation and after 24 hours, modified Thrombolysis in Cerebral Infarction (mTICI) score, any intraparenchymal hemorrhage at 24 hours CT, modified Rankin Score (mRS) after 3 months.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eTechnique and protocols\u003c/h2\u003e \u003cp\u003eAll CT imaging was obtained on a 2 \u0026times; 64 detector rows Dual Source scanner. Non-contrast CT was acquired using the axial technique with 120 kVp, 100\u0026ndash;350 auto-mAs, and 5-mm section thickness reconstructions. CTA was acquired using triple phase technique after 60 mL of 350 mgI/ml iodinated contrast medium injection at a 4 mL/s flow rate. The first phase, from aortic root to the vertex, was acquired using bolus tracking technique with 5 seconds delay after a 100 HU threshold was reached in the aortic arch, whereas the second and the third phases, limited to the intracranial circle, were acquired with a 8 second fix delay from the previous ones. In case of unknown stroke onset time or beyond 6 hours from onset time, CT perfusion was used to select patients according to DAWN and DEFUSE-3 randomized clinical trials criteria followed by a single-phase CTA from aortic arch to the intracranial circulation [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eEndovascular treatment\u003c/h2\u003e \u003cp\u003eEndovascular procedures were performed on a biplane X-ray system by 1 out of 4 radiologists with 5 to 15 years of experience in stroke interventions. All patients underwent a preliminary angiographic examination to confirm and precisely localize the occlusion and to guide the subsequent treatment. Pseudo-occlusion was diagnosed by documenting sluggish, slow and pulsatile progressions of contrast into the ICA. In those cases, a diagnostic 5F catheter or a large-bore aspiration catheter was advanced to look for a terminal occlusion.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eImage analysis\u003c/h2\u003e \u003cp\u003eQualitative image analysis was performed by two neuroradiologists, with 13 and 10 years of experience in stroke imaging and treatment, unaware of patients\u0026rsquo; clinical data, on a dedicated workstation using commercially available software (Syngo.via Version VB30, Siemens, Erlangen, Germany). They were asked to assess ASPECTS (0\u0026ndash;10) on unenhanced brain CT, baseline and at 24 hours, and collateral score (good/intermediate/poor collaterals) on CTA, according to the classification by Tan et al [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Discrepancies were solved by consensus. Post-procedural DSA imaging was also evaluated to determine revascularization according to the mTICI score.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eData are reported as means with standard deviations or medians for continuous variables. Continuous variables were compared with independent-samples two-tailed t-test, dichotomous variables with Fisher\u0026rsquo;s exact test. p-value inferior to 0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eOn a total of 493 endovascular stroke procedures, 95 consecutive patients with absent opacification of ICA at baseline CTA were included. 52 (55%) had true occlusion of cervical ICA associated to a large intracranial vessel occlusion (41 atheromatic, 7 dissected, 4 embolic), 43 (45%) had distal ICA occlusion presenting as pseudo-occlusion (PO), the latter being all embolic. Baseline NIHSS, ASPECT score in admission, and intravenous administration of rtPA did not significantly differ between the two groups. Compared to the PO group, collateral circulation at CTA was moderate to good in 67% of cases (vs 29%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and mean infarction volume measured as ASPECT score at 24h control CT was lower: 2.7 vs 5.5 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Good outcome after 3 months, defined as modified Rankin Score 0\u0026ndash;2, was more likely in patients with tandem occlusion (TO) compared to patients with pseudo-occlusion (44.9 vs 14.6%; p 0.003). Notably, there was no significant difference in terms of revascularization (75% in TO vs 67.4% in PO) or intracranial parenchymal hemorrhage at 24h CT (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Mortality was almost double in PO group but not statistically significant.\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\u003eSD\u0026thinsp;=\u0026thinsp;standard deviation; av\u0026thinsp;=\u0026thinsp;average; CS\u0026thinsp;=\u0026thinsp;collateral score according Tan IYL et al [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]; TICI\u0026thinsp;=\u0026thinsp;thrombolysis in cerebral infarction; ASPECT\u0026thinsp;=\u0026thinsp;Alberta stroke program early CT; IPH\u0026thinsp;=\u0026thinsp;intracranial parenchymal hemorrhage; SAH\u0026thinsp;=\u0026thinsp;subarachnoid hemorrhage; mRS\u0026thinsp;=\u0026thinsp;modified Rankin Scale.\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrue occlusion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePseudo-occlusion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value (test)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBASELINE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex, male (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35 (67.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32 (74.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, years av (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e64 (14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e73 (12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, years min-max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u0026ndash;88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43\u0026ndash;91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNIHSS on admission, av\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18 (n\u0026thinsp;=\u0026thinsp;38)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21 (n\u0026thinsp;=\u0026thinsp;36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASPECT, av\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (n\u0026thinsp;=\u0026thinsp;51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCS score, av\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e2.0 (n\u0026thinsp;=\u0026thinsp;51)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0155 (Chi-square)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCS score 2\u0026ndash;3 (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e33/49 (67)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e12/41 (29)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0006 (Fisher\u0026rsquo;s exact)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEtiology (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAtheromatous 41 (79)\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eDissective 7 (13.5)\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eEmbolic 4 (7.5)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eEmbolic 43 (100)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.00001 (Fisher\u0026rsquo;s exact)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eINTERVENTION\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntravenous rt-PA (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29/40 (72.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19/31 (61)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTICI score 2B-3 (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39/52 (75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29/43 (67.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOUTCOME\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eASPECT after 24 h, av\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e5.5 (n\u0026thinsp;=\u0026thinsp;50)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e2.7 (n\u0026thinsp;=\u0026thinsp;42)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0004 (Mann-Whitney's)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eASPECT 6\u0026ndash;10 after 24 h (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e31/50 (62)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e9/42 (21.4)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0001 (Fisher\u0026rsquo;s exact)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIPH after 24h (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7/52 (13.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9/43 (20.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAH after 24h (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4/52 (7.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7/43 (16.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003emRS 0\u0026ndash;2 at 90 days (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e22/49 (44.9)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e6/41 (14.6)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0027 (Fisher\u0026rsquo;s exact)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003emRS 0\u0026ndash;2/surv at 90 days (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e22/38 (57.9)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e6/24 (25)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.0179 (Fisher\u0026rsquo;s exact)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMortality at 90 days (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11/49 (22.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17/41 (41.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eMechanical thrombectomy dramatically changed the outcome of patients with acute ischemic stroke due to anterior circulation intracranial large vessel occlusion. Randomized clinical trials included patients with terminal ICA occlusion and M1 tract of middle cerebral artery, also with concomitant cervical tract ICA occlusion or severe stenosis (tandem lesions) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Prespecified subgroup analysis found a higher treatment effect for patients with stroke due to ICA occlusion in comparison with more distal locations (common Odds Ratio 3.96) as well as for patients with tandem lesions (cOR 2.95) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], but ICA occlusion has also been reported as negative prognostic factor [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Terminal carotid occlusion and tandem occlusions were also associated to higher complication rate during mechanical thrombectomy in the French ETIS registry, being predictors of embolus to new territory [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Similarly, the Italian Registry of Endovascular Stroke Treatment reported higher risk of subarachnoid hemorrhage/arterial perforation rate and higher risk of developing symptomatic intracranial hemorrhage in patients treated for distal intracranial carotid occlusion [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eICA occlusions encompass different clinical conditions and can be misinterpreted [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. ICA can be involved in many different ways in patients undergoing endovascular treatment for acute ischemic stroke: distal occlusion involving the apical tract are usually embolic and frequently caused by the migration of massive thrombi originating from cardiac chambers due to atrial fibrillation, whereas proximal occlusions ae usually atheromatous or due to dissection [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Isolated apex occlusions show different presentations at CT-angiography according to the opacification of the upstream cervical tract, due to presence or absence of outflow vessels: if outflow arteries as the ophtalmic or the posterior communicating branches are absent, there is no progression of contrast medium into the vessel simulating a proximal ICA occlusion (pseudo-occlusion). If outflow vessels are thin with a limited downstream capacity, there can be a slow progression of contrast media that can be documented as a contrast gradient along the ICA or a late opacification at multiphase CTA [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Although morphology of occlusion at CTA and multiphase CTA have been suggested to improve diagnostic accuracy, pseudo-occlusions remain a significant issue with angiographic microcatheter exploration being often required for the proper diagnosis [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In this study, we decided to adopt a very strict definition of pseudo-occlusion, excluding patients with a contrast gradient along ICA which makes differential diagnosis more obvious, and we did not consider later phase acquisition.\u003c/p\u003e \u003cp\u003eAs suggested by multiple studies, pseudo-occlusion is a particularly unfavorable presentation of acute ischemic stroke in patients treated both with intravenous thrombolysis and mechanical thrombectomy [\u003cspan additionalcitationids=\"CR22 CR23\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. These authors constantly reported lower revascularization rate in patients with pseudo-occlusions after endovascular treatment, in contrast with our experience. We reported unfavorable outcome for patients with pseudo-occlusions without a significant difference in terms of reperfusion rates. Our technical approach was not different to treat the two conditions in the study period: aspiration first and stentretriever-assisted thrombectomy only if necessary, and in tandem occlusion intracranial first treatment and carotid stenting only in limited selected cases.\u003c/p\u003e \u003cp\u003eCollateral status is a well-known prognostic factor in patients undergoing endovascular treatment for acute ischemic stroke [\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. For example, composition of Willis circle can determine different outcomes in patients with distal ICA occlusion [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Poor collateral circulation is a possible explanation for the unfavorable outcome for patients with pseudo-occlusion, the latter being associated with slow or absent flow through the ICA [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Multiphase CTA seems to be superior to single-phase CTA to evaluate collateral circulation, but due to radiation dose exposure it should be used in alternative to CT perfusion [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. MCTA could also help to identify pseudo-occlusion [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], but this only applies to slow-flow cases and not to cases with completely absent inflow [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Our study found a relevant difference in terms of clinical outcome and collateral circulation evaluated at single-phase CT-angiography, which was available both in patients who underwent CT perfusion (beyond 6 hours from stroke onset time and unknown onset time) and multiphase CT angiography (within 6 hours from stroke onset time). Interestingly this observation, if confirmed by larger studies, could be widely adopted on the basis of a fast and easy examination.\u003c/p\u003e \u003cp\u003eOur study is firstly limited by its retrospective design. Secondly, we adopted a stricter definition of pseudo-occlusions than usual. Moreover, it reports data from a single stroke center and images were not evaluated by an independent core laboratory. A larger multicenter study is needed to confirm our results.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003ePseudo-occlusion of cervical internal carotid artery in patients with acute ischemic stroke is likely to be associated with worst prognosis and poorer collateral circulation. This imaging feature could represent an additional variable to consider when selecting stroke patients for endovascular treatment.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interest\u003c/h2\u003e \u003cp\u003eOn behalf of all authors, the corresponding author states that there is no conflict of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAC and CC designed the study and wrote the main manuscript. MB, EF and EDO helped to collect and elaborate data. GNG and FL contributed to statistical analysis and data interpretation. BP has drafted the manuscript. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKappelhof M, Marquering HA, Berkhemer OA, et al. Accuracy of CT angiography for differentiating pseudo-occlusions from true occlusions or high-grade stenosis of the extracranial ICA in acute ischemic stroke: a retrospective MR CLEAN substudy. AJNR Am J Neuroradiol 2018; 39:892\u0026ndash;898.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDiouf A, Fahed R, Gaha M, et al. Cervical internal carotid occlusion versus pseudo-occlusion at CT-angiography in the context of acute ischemic stroke: an accuracy, interobserver and intraobserver agreement study. Radiology 2018; 286:1008\u0026ndash;1015.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrossberg JA, Haussen DC, Cardoso FB, et al. Cervical carotid pseudo-occlusions and false dissections: intracranial occlusions masquerading as extracranial occlusions. Stroke 2017 48:774\u0026ndash;777.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMenon BK, Smith EE, Modi J, et al. Regional leptomeningeal score on TC angiography predicts clinical and imaging outcomes in patients with acute anterior circulation occlusions. AJNR Am J Neuroradiol 2011; 32:1640\u0026ndash;1645.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTan IYL, Demchuk AM, Hopyan J, et al. CT angiography Clot Burden Score and Collateral Score: correlation with clinical and radiologic outcomes in acute middle cerebral artery infarct. AJNR Am J Neuroradiol 2009; 30(3):525\u0026ndash;531.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoyal M, Menon BK, van Zwam WH, et al. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials. Lancet 2016; 387:1723\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePowers WJ, Rabinstein AA, Ackerson T, et al. Guidelines for the early management of patients with acute ischemic stroke: 2019 update to the 2018 guidelines for the early management of acute ischemic stroke: a guideline for healthcare professionals from the American heart association/American stroke association. Stroke 2019; 50:e344-418.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTurc G, Bhogal P, Fisher U, et al. European Stroke Organisation (ESO) - European Society for Minimally Invasive Neurological Therapy (ESMINT) guidelines on mechanical thrombectomy in acute ischemic stroke. JNIS 2019; 11:535\u0026ndash;538.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMalhotra K, Goyal N, Tsivgoulis G et al. Internal carotid artery occlusion: pathophysiology, diagnosis, and management. Curr Atheroscler Rep 2017; 19:41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhatia R, Hill MD, Shobha N, et al. Low rates of acute recanalization with intravenous recombinant tissue plasminogen activator in ischemic stroke: real-world experience and a call for action. Stroke 2010; 41(10):2254\u0026ndash;2258.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFaught WE, van Bemmelen PS, Mattos MA, et al. Presentation and natural history of internal carotid artery occlusion. J Vasc Surg 1993; 18(3):512\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOlivot JM, Heit JJ, Mazighi M, et al. What predicts poor outcome after successful thrombectomy in early time window? J NeuroIntervent Surg 2021; 14:1051\u0026ndash;1055.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeng G, Xiao J, Yu H, et al. Predictors of futile recanalization after endovascular treatment in acute ischemic stroke: a meta-analysis. J NeuroIntervent Surg 2021; 14:881\u0026ndash;885.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNgankou EH, Gory B, Marnat G, et al. Thrombectomy complications in large vessel occlusions: incidence, predictors, and clinical impact in the ETIS registry. Stroke 2021; 52:e764-e768.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalsano G, Pracucci G, Mavilio L, et al. Complications of mechanical thrombectomy for acute ischemic stroke: Incidence, risk factors, and clinical relevance in the Italian Registry of Endovascular Treatment in acute stroke. Int J Stroke 2020; 16(7):818\u0026ndash;827.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWareham J, Crossley R, Barr S, Mortimer A, et al. Cervical ICA pseudo-occlusion on single phase CTA in patients with acute terminal ICA occlusion: what is the mechanism and can delayed CTA aid diagnosis? J NeuroIntervent Surg 2018; 0:1\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFernandez-Gomez M, Gallo-Pineda F, Hidalgo-Barranco C, et al. Acute intracranial internal carotid artery occlusion: Extension and location of the thrombus as an influencing factor in Computed Tomography angiography findings. Eur J Radiol Open 2023; 10:100462.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim HJ, Kwak HS, Chung GH, et al. Differentiating pseudo-occlusion from true occlusion of the proximal internal carotid artery in acute ischemic stroke on CT angiography. Clin Neurol Neurosurg 2019; 185:105495.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePrakkamakul S, Pitakvej N, Dumrongpisutikul N, et al. Mid-cervical flame-shaped pseudo-occlusion: diagnostic performance of mid-cervical flame-shaped extracranial internal carotid artery sign on computed tomographic angiography in hyperacute ischemic stroke. Neuroradiol 2017; 59:989\u0026ndash;996.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChoi JH, Jang J, Koo J, et al. Multiphasic computed tomography angiography findings for identifying pseudo-occlusion of the internal carotid artery. Stroke 2020; 51:2558\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Z, Zhang M, Shi F, et al. Pseudo-occlusion of the internal carotid artery predicts poor outcome after reperfusion therapy. Stroke 2018; 49:1204\u0026ndash;1209.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJung WS, Lee JS, Solander S. et al. Pseudo-occlusion of the internal carotid artery in acute ischemic stroke: clinical outcome after mechanical thrombectomy 2020; 10:2832.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJang J, Lee JK, Koo J, et al. Acute ischemic stroke caused by internal carotid artery occlusion: impact of occlusion type on the prognosis. World Neurosurg 2022; 164:e387-e396.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNi H, Yang T, Jia Z, et al. Outcomes in acute ischemic stroke patients undergoing endovascular thrombectomy: cervical internal carotid artery pseudo-occlusion vs. true occlusion. Front Neurol 2023; 13: 1106358.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUniken Venema SM, Dankbaar JW, van der Lugt A, et al. Cerebral collateral circulation in the era of reperfusion therapies for acute ischemic stroke. Stroke 2022; 53:3222\u0026ndash;32343.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee JS, Bang OY, et al. Collateral status and outcomes after thrombectomy. Transl Stroke Res. 2023; 14:22\u0026ndash;374.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBracco S, Zanoni M, Casseri T, et al. Endovascular treatment of acute ischemic stroke due to tandem lesions of the anterior cerebral circulation: a multicentric Italian observational study. Radiol med 2021; 126, 804\u0026ndash;817.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee SU, Hong JM, Kim SY, et al. Differentiating carotid terminus occlusions into two distinct populations based on willisian collateral status. J Stroke 2016; 18(2):179\u0026ndash;186.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBusto G, Morotti A, Carlesi E, et al. Pivotal role of multiphase computed tomography angiography for collateral assessment in patients with acute ischemic stroke. Radiol Med 2023; 128:944\u0026ndash;959.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDundamadappa S, Iyer K, Agrawal A, et al. Multiphase CT angiography: a useful technique in acute stroke imaging\u0026mdash;collaterals and beyond. AJNR Am J Neuroradiol 2021; 42(2): 221\u0026ndash;227.\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":"Acute ischemic stroke, Endovascular treatment, Mechanical thrombectomy, Collateral circulation, CT angiography, Stroke imaging","lastPublishedDoi":"10.21203/rs.3.rs-4307068/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4307068/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eOcclusion of distal internal carotid artery can simulate a proximal occlusion of its cervical tract at CT angiography in patients with acute ischemic stroke, i.e. pseudo-occlusion. As true and false carotid occlusions can have similar presentation at non-invasive imaging of a patient undergoing endovascular treatment for stroke, our study aimed to evaluate clinical and technical differences of these conditions and the possible consequences of a misdiagnosis.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eWe retrospectively reviewed consecutive patients who underwent mechanical thrombectomy for acute ischemic stroke in a single center between July 2015 and July 2021 and included patients with absent opacification of cervical carotid artery at CT-angiography. Digital subtraction angiography (DSA) imaging and procedural data were evaluated to define the actual localization of occlusion. We compared imaging and clinical data of patients with true and false carotid occlusion, including collateral circulation at CTA, revascularization grade and clinical outcome at 3 months.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003e95 patients were included, 52 (49%) had true occlusion of cervical internal carotid artery. Compared to the pseudo-occlusion group, collateral circulation at CTA was moderate to good in 67% of cases (vs 29%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and mean ASPECT score at 24h was 5.5 vs 2.7 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Modified Rankin scale 0\u0026ndash;2 at 90 days was more frequent in patients with true occlusion compared to patients with pseudo-occlusion (44.9 vs 14.6%; p 0.003).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003ePseudo-occlusion of cervical internal carotid artery in patients with acute ischemic stroke seem to be associated with worst prognosis and poorer collateral circulation.\u003c/p\u003e","manuscriptTitle":"Mechanical thrombectomy for acute ischemic stroke with absent opacification of the cervical internal carotid artery at CT-angiography: pathophysiology and outcome","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-02 19:04:09","doi":"10.21203/rs.3.rs-4307068/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":"382f4bf2-0929-433f-890f-b8b964ce686a","owner":[],"postedDate":"May 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":31327584,"name":"Health sciences/Anatomy/Nervous system/Brain"},{"id":31327585,"name":"Biological sciences/Neuroscience"},{"id":31327586,"name":"Health sciences/Neurology"}],"tags":[],"updatedAt":"2024-08-16T05:21:06+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-02 19:04:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4307068","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4307068","identity":"rs-4307068","version":["v1"]},"buildId":"re_ckhLnmML6MCF96OHNJ","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}