Observation of the the progression of tension in intracranial arachnoid cyst: A case report and review of literature

Observation of the the progression of tension in intracranial arachnoid cyst: A case report and review of literature | 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 Case Report Observation of the the progression of tension in intracranial arachnoid cyst: A case report and review of literature Zhixiong Lin, Jintao Chen, Hanrong Dong, Bei Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6780400/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Mar, 2026 Read the published version in BMC Pediatrics → Version 1 posted 16 You are reading this latest preprint version Abstract Arachnoid cysts (ACs) are common benign intracranial space-occupying lesions in children can be categorized into tensional and non-tensional cysts based on imaging features. The majority of ACs are clinically silent and remain static in size; however, some intracranial ACs may gradually increase in size. However, the relationship between tension in cyst and cyst enlargement is currently unclear. Due to the rarity of observed progression of tension in intracranial ACs, controversies persist regarding when and how to perform surgery. We present a rare case of a progressive increase in head circumference over one year in a 15-month-old child caused by growing tensional AC at the left cerebellopontine angle. Brain magnetic resonance imaging (MRI) at 6 days after birth revealed a small non-tension AC at the left cerebellopontine angle with no apparent compression of adjacent brain tissue and clear sulci and gyri. At 15 months, the MRI revealed a significant enlargement of AC, brain stem was displaced, sulci of the adjacent brain tissue disappeared, and the cyst-brain tissue interface displayed a tensional arc-type change, accompanied by obstructive hydrocephalus. Through fenestration, the AC was reduced, exhibiting non-tension changes, significantly alleviating pressure on adjacent brain tissue, and hydrocephalus significantly improved. Subsequent follow-ups showed no obvious abnormalities. In conclusion, the degree of tension seen in AC imaging is the result of cyst enlargement, guiding surgical intervention and postoperative efficacy evaluation. Arachnoid cyst “Ball-valve” mechanism Congenital benign cysts Endoscopic fenestration case report Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Arachnoid cysts (ACs) are common benign intracranial space-occupying lesions in children. They are pouch-like intra-arachnoid masses containing cerebrospinal fluid (CSF), primarily located in the CSF cisterna and the main cerebral fissure. Intracranial arachnoid cysts (IACs) constitute 1% of intracranial space-occupying lesions and affect 2.6% of the population under 18 years of age, with greater than 90% being asymptomatic [ 1 – 3 ] . It is believed that congenital ACs may form in the early stages of subarachnoid space development, stemming from abnormal arachnoid replication and division during the embryonic period, and are associated with irregular CSF flow [ 2 , 4 ] . The majority of congenital ACs are clinically silent and remain static in size; however, some IACs may gradually increase in size. Presently, research data from different centers indicate a wide variation in the proportion of enlarged IACs within the total IAC population, ranging from 0.73–19.7% [ 1 , 5 – 8 ] . Among 488 cases, only three demonstrated an increase during follow-up, clinically, changes in the size of IACs were rarely observed, with the majority remaining stable [ 5 ] . Yin et al. [ 6 ] reported on 60 cases of fetal IACs using conventional ultrasound, with thirty cases first detected during the second trimester and the remaining thirty during the third trimester. Ultrasound and magnetic resonance imaging (MRI) follow-ups revealed that IACs increased in 20% of cases, remained stable in 65%, and decreased in 15%. Another study [ 7 ] reported on the follow-up of 86 cases of IACs in children under the age of 5, with 17 cases showing enlargement. Among them, 11 cases enlarged without requiring surgery, 6 cases did not continuously enlarge, and 3 cases reduced in size. Al-Holou et al. [ 8 ] conducted a follow-up on 203 adult cases of IACs and found that IACs enlarged in 2.3% (5 cases), decreased in 0.9% (2 cases), and aggravated in only 0.9% (2 cases). These suggested that enlargement of IAC in adults is rare and should be distinguished from that in children, especially those under the age of 3. Although most IACs remain static throughout their lifespan, some ACs may enlarge under pressure, exerting a space-occupying effect on adjacent neural structures [ 9 ] . Among these cases, age stands out as the sole definitive effective factor. Based on imaging features ACs were divided into tensional and non-tensional cysts [ 5 ] . This classification system focuses on the role of tension in cyst enlargement and determining the appropriate time for surgical intervention. Nevertheless, due to the inability to clinically observe the progression of tension, the relationship between tension in cyst and cyst enlargement is currently unclear. The key words "growing", "Space-Occupying", "Increasing Arachnoid Cysts", "Increasing Arachnoid Cyst", "Cystic Lesions" was searched in PubMed and Web of Science for English literature. The starting point of search for English databases was unrestricted and ended in February 2024. Two independent reviewers searched and screened the relevant literature abstracts, and then the relevant studies were reviewed in full text and the data were extracted and checked. Out of the 15 articles reviewed, only 7 were considered eligible for inclusion as they discussed the relationship between tension in cyst and cyst enlargement of Acs [ 10 – 16 ] , the remaining 8 articles mentioned tension but did not explore the relationship between tension in cysts and cyst enlargement of ACs, so they were excluded. (see Table 1 ). Of the 7 articles, only 1 reported on hydrocephalus because of a voluminous left frontotemporal cyst with an important mass effect on the midline and lateral ventricles [ 11 ] , but none of which demonstrated the whole process. In this report, we presented a case of a small non-tension AC at the left cerebellopontine angle detected at birth. This cyst gradually developed into a giant tension AC, and subsequently shrank after AC cystostomy. Table 1 Summary of cases of tensional arachnoid cyst. Ref. author year age symptoms lesion pathogenesis 1 Tahir MZ [ 10 ] 2012 60y headaches, vomiting, seizures and altered state of consciousness LT uncal herniation 2 Graillon T [ 11 ] 2013 81y progressive hemiplegia and aphasia LT hydrocephalus 3 Gadoth N [ 12 ] 2014 1m left tonic conjugate gaze deviation LT falcial herniation 4 Bhattarai HB [ 13 ] 2023 35y sudden loss of consciousness, anisocoria, and right hemiparesis LT uncal herniation 5 Balani A [ 14 ] 2015 70y headaches, vomiting and seizures followed by sudden onset loss of consciousness RT uncal herniation 6 Peng P [ 15 ] 2020 67y dizziness, left lower limb numbness RT compression 7 Karaaslan B [ 16 ] 2019 1m peripheral facial palsy RCPA compression LT: left temporal; RT: right temporal; RCPA: right cerebellopontine angle Case presentation A 15-month-old child was admitted to the hospital due to a progressive increase in head circumference over the past year. Brain MRI performed 6 days after birth revealed a small AC in the left pontocerebellar region, without obstructive hydrocephalus at that time (Fig. 1 A, 1 B, 1 C). At the age of 15 months, the child exhibited a progressive increase in head circumference, measuring 49.7 cm. Physical examination revealed retarded development, an abnormal head shape with a dilated and unclosed anterior fontanelle, measuring about 5*5 cm, and an inability to walk. Brain MRI showed a giant subarachnoid AC in the left pontocerebellar region, constricting the brain stem and left cerebellum. At the same time, CSF film demonstrated a weak CSF flow velocity signal in the midbrain aqueduct, accompanied by ventricle and fontanelle enlargement (Fig. 1 D, 1 E, 1 F, 3 A). Due to the obstructive hydrocephalus caused by the AC, AC fenestration was performed under general anesthesia on July 12, 2023. During the operation, upon opening the dura mater, the AC wall exhibited high tension (Fig. 2 A). Upon piercing the AC wall, colorless clear liquid was ejected. Following the slow release of CSF, the AC wall collapsed. Upon full opening of the lateral AC wall, the AC wall of the cerebellum and the inner side of the brain stem appeared to bulge outward. Recognizing the reduced pressure in the AC cavity after opening, CSF accumulated outside the AC wall, forming an inverse bulge into the AC like a unidirectional valve (Fig. 2 B). To establish communication with the cisterna ambiens, the walls of the AC were further opened at the medial and ventral parts of the cerebellar brainstem (Fig. 2 C, 2 D). Brain MRI 2 months after the operation indicated a reduction in the AC cavity, alleviation of the mass effect, and a significant decrease in the child's head circumference (Fig. 1 G, 1 H, 1 I, 3 C). Discussion Based on imaging features AC were divided into tensional and non-tensional cysts [ 5 ] . This classification system focuses on the role of tension in cyst enlargement and determining the appropriate time for surgical intervention. This case report clearly illustrates the relationship between tension in cyst and cyst enlargement. Although the mechanism driving ACs enlargement remains unclear, several postulated mechanisms include: (1) The ball valve hypothesis: There may be an anatomic communication that acts functionally as a one-way valve between the cyst and the subarachnoid space. (2) Osmotic gradient between cystic content and cerebro-spinal fluid: This theory is not supported by evidence because the cystic content is similar in composition to CSF. Congenital arachnoid cysts are maldevelopmental anomalies and contain clear CSF-like fluid. In acquired cysts the intracystic fluid may be hemosiderin-stained or may contain inflammatory cells with a possible gradient. (3) Fluid production by the cells lining the walls of the cysts: There is some morphologic and ultracytochemical evidence to support the secretory nature of the cyst wall. The argument against continuous secretion is that the cysts often remain static in size and sometimes disappear, thus demonstrating that secretion is neither universal nor, likely, the only mechanism involved [ 17 – 20 ] . Generally, if an AC enlarges, it can induce symptoms such as raised intracranial pressure, nausea and vomiting, focal neurologic deficits, or hydrocephalus [ 9 , 21 , 22 ] . Surgical intervention is typically recommended for symptomatic patients, depending on the AC effect, often determined by the tension of the AC. However, due to the infrequent observation of the progression of intracranial tensional AC, controversies persist regarding when and how to perform surgery. In this case, we posit that tension in the AC results from its progression and is associated with a unidirectional valve within the subarachnoid space. Speculatly, a small section of the AC wall forms a one-way valve. When intracranial pressure increases, which may caused by crying, exertion, or the Valsalva maneuver, the responsiveness of the subarachnoid space to changes in venous pressure might also lead to increased filling of the cysts and contribute to enlargement, preventing its outward flow due to the valve's unidirectional nature (Fig. 4 A). Additionally, the brain tissue outside the cyst exerts pressure on the AC wall, which results in a pressure balance between the inside and outside of the AC, ultimately forming a stable tensional cyst (Fig. 4 B). Consequently, IACs are often incidentally diagnosed during brain computed tomography or MRI scans conducted for unrelated symptoms. The stable appearance of the AC on imaging suggests a progression to a balanced state of both internal and external pressures within the AC. In the case of slit valves, pulsations of CSF flowing from caudad to cephalad in the prepontine cistern during the cardiac cycle lifted the wall of these cysts, increasing the opening of the slit valve and resulted in net flow of CSF into the cyst. Normal backflow of CSF into the spinal compartment is relatively blocked during the cardiac cycle, due to apposition of the slit valve against the tension exerted by the cyst way and adjacent brain tissue. Thus, this imbalance in oscillatory flow of CSF between the craniospinal compartments further supports the slit valve as being responsible for the increase in size of suprasellar prepontine arachnoid cysts. Clinical data showed that tensional AC tend to become smaller after fenestration or shunt surgery, leading to the alleviation of corresponding clinical symptoms. If there is bidirectional communication in the AC, it should present non-tension characteristics, whereas the presence of a one-way valve would lead to gradual enlargement in the early stage, demonstrating tensional changes. Studies have demonstrated the existence of only a few small capillaries on the AC wall, lacking cells capable of clear fluid secretion. Moreover, the properties of AC cavity fluid and CSF proteins are roughly similar [ 23 , 24 ] . Additionally, the majority of ACs do not increase in size. Therefore, we consider the mechanisms of gradual AC enlargement caused by fluid secretion from the AC wall or gradient differences to be unlikely. Under normal circumstances, high-pressure liquid will flow to a low-pressure area. Following the principles of mechanics, generally enlarged ACs are considered tension cysts. The primary surgical methods for AC intervention include craniotomy with cyst wall resection or AC fenestration, endoscopic cystocisternostomy, and cyst-peritoneal shunt (CPS) [ 5 , 25 ] . A recent meta-analysis revealed no significant difference in the impact of these surgical methods on the quality of life of patients after 5 years [ 26 ] . However, there were variations in efficacy among the three surgical methods. The reduction rate of ACs after craniotomy was 92%, with a near-total disappearance rate of 51%. For endoscopic fenestration, the reduction rate was 75%, and the near-total disappearance rate was 39%. CPS demonstrated the highest reduction rate of 100%, with a near-total disappearance rate of 89% [ 27 ] . In terms of cyst disappearance and reduction rates, CPS exhibited the most favorable outcomes. However, serious complications, such as shunt dependency syndrome (SDS), can occur after CPS [ 28 – 30 ] . Shim et al. [ 31 ] reported that among 19 patients undergoing CPS, 8 developed SDS, with an average onset time of 6.1 years post-operation, reaching a proportion as high as 42%. In 11 cases with a complete disappearance of the cyst, attempting shunt removal by ligation was successful in 8 cases. Ventriculoperitoneal shunt not only effectively alleviates SDS through the reconstruction of the CSF circulation pathway but also prevents the enlarged cysts from increasing in size simultaneously. These conditions further suggest that the cyst fluid primarily originates from extracapsular CSF through a one-directional pathway, contradicting the theories of intracystic fluid production by secreting cells or fluid movement following an osmotic gradient. Therefore, ACs can be comprehended as a special type of hydrocephalus- local hydrocephalus. In this case, the cyst cavity gradually reduced in size and exhibited non-tensional changes after the subarachnoid fistula of the cyst (Fig. 4 C). This reduction was attributed to the pressure within the AC cavity being lower than the pressure surrounding the AC, leading to the retraction of the AC wall. Consequently, this case indirectly suggested that non-tensional ACs may not necessitate surgical intervention. Patients with SDS or slit-like ventricles after CPS pose significant treatment challenges. Therefore, the optimal approach is to restore the physiological flow of CSF in the capsule. Conclusion The AC is characterized by an abnormal accumulation of CSF in the CSF circulation pathway, akin to a localized hydrocephalus. The tensional features observed in AC imaging reflect the progression of the cyst. The severity of tension serves as the basis for surgical intervention and a critical index for assessing postoperative efficacy. The optimal treatment is arachnoid cystostomy, a procedure that not only restores the physiological flow and circulation of CSF within the capsule but also addresses the space-occupying effect of the AC, thereby avoiding the development of long-term SDS. Abbreviations AC arachnoid cyst CPS cyst-peritoneal shunt CSF cerebrospinal fluid IACs intracranial arachnoid cysts MRI magnetic resonance imaging SACs spinal arachnoid cysts SDS shunt dependency syndrome. Declarations Ethics approval and consent to participate：Ethical approval was granted by the Ethics Committee of Fujian Sanbo Funeng Brain Hospital (No. FJSBNK-YJ-2025-002-01). Patients provided signed informed consent to participate in the study. Consent for publication：Informed consent for publication of clinical details and/or clinical images was obtained from the parents of the patient. Availability of data and materials：The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. Competing Interests：The authors report no conflict of interest. Funding：None. Author Contribution：ZX. L, JT. C, HR. D, B. L: conception and design, acquisition of data, analysis and interpretation of data, drafting of the article, and critically revising the article; Reviewed submitted version of the manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: ZX. L. Acknowledgments：None. References Sarwar S, Rocker J. Arachnoid cysts in paediatrics. Curr Opin Pediatr 2023, 35, 288-295. http://doi.org/10.1097/MOP.0000000000001219. Carbone J, Sadasivan AP. Intracranial arachnoid cysts: Review of natural history and proposed treatment algorithm. Surg Neurol Int 2021, 12, 621. http://doi.org/10.25259/SNI_946_2021. Mustansir F, Bashir S, Darbar A. 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Cite Share Download PDF Status: Published Journal Publication published 05 Mar, 2026 Read the published version in BMC Pediatrics → Version 1 posted Editorial decision: Revision requested 01 Aug, 2025 Reviews received at journal 19 Jul, 2025 Reviews received at journal 12 Jul, 2025 Reviewers agreed at journal 10 Jul, 2025 Reviews received at journal 10 Jul, 2025 Reviews received at journal 09 Jul, 2025 Reviewers agreed at journal 02 Jul, 2025 Reviewers agreed at journal 02 Jul, 2025 Reviews received at journal 29 Jun, 2025 Reviewers agreed at journal 26 Jun, 2025 Reviewers agreed at journal 25 Jun, 2025 Reviewers invited by journal 24 Jun, 2025 Editor assigned by journal 18 Jun, 2025 Editor invited by journal 30 May, 2025 Submission checks completed at journal 30 May, 2025 First submitted to journal 30 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-6780400","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":477023369,"identity":"a3786347-dd98-494b-ba98-a4b74e4b727c","order_by":0,"name":"Zhixiong Lin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAsklEQVRIiWNgGAWjYBACPmYQWQHl8RCjhQ2s5QxJWkAEYxtJWth5D3/mnWcnrzsjgfHB2zYGeXPCDuNLMJy5Ldlw240EZsO5bQyGOxsIauExSPi47UCC2Y0ENmneNoYEgwNEaDmQOAeshf03sVoMGz42QGxhJlaLMeOMY0C/nHnYLDnnnIThBkJa+PnPGH/mqbGTNzuefPDDmzIbeYK2IAHGBiAhQbz6UTAKRsEoGAW4AQC3xTaeECuDuQAAAABJRU5ErkJggg==","orcid":"","institution":"Capital Medical University","correspondingAuthor":true,"prefix":"","firstName":"Zhixiong","middleName":"","lastName":"Lin","suffix":""},{"id":477023371,"identity":"39fc445f-258d-4b16-935c-a798fdf8a434","order_by":1,"name":"Jintao Chen","email":"","orcid":"","institution":"Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Jintao","middleName":"","lastName":"Chen","suffix":""},{"id":477023373,"identity":"a5b10ea6-351e-4b47-aad0-dcec16aead32","order_by":2,"name":"Hanrong Dong","email":"","orcid":"","institution":"Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Hanrong","middleName":"","lastName":"Dong","suffix":""},{"id":477023375,"identity":"f6739571-61e7-4227-bdfd-190410a4a254","order_by":3,"name":"Bei Liu","email":"","orcid":"","institution":"Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Bei","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2025-05-30 02:53:39","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6780400/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6780400/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12887-026-06618-8","type":"published","date":"2026-03-05T15:59:43+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85842421,"identity":"183a87a6-6b1b-4e65-a83b-e61ff13cf994","added_by":"auto","created_at":"2025-07-02 09:22:23","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":188250,"visible":true,"origin":"","legend":"\u003cp\u003e(A-C) Brain MRI 6 days after birth revealed a small cyst at the left cerebellopontine angle (star), with no obvious compression of the adjacent brain tissue (arrow). (D-F) Brain MRI at the age of 1 year and 3 months revealed a significant enlargement of the left cerebellopontine angle cyst (star) and obvious compression of the adjacent brain tissue (triangle), accompanied by obstructive hydrocephalus. (G-I) Brain MRI 2 months after surgery showed a reduced cyst (star) and visible sulci and gyrus (arrow).\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780400/v1/4b5abdd70ab8c29fb0dfcfbc.jpg"},{"id":85842447,"identity":"b3bb7d67-f63d-4f65-b2da-21ebc6e01c4f","added_by":"auto","created_at":"2025-07-02 09:22:27","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":116063,"visible":true,"origin":"","legend":"\u003cp\u003eIntraoperative photography of the AC showed \u003cstrong\u003e(A)\u003c/strong\u003e the high tensional cyst wall; \u003cstrong\u003e(B)\u003c/strong\u003eaccumulated CSF outside the cyst wall, forming an inverse bulge into the cyst, with reduced pressure in the cyst cavity after opening; and \u003cstrong\u003e(C, D)\u003c/strong\u003eseveral openings made on the cyst wall. (E) Pathological images of the cyst wall.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780400/v1/9c406071ed68b0ab86820be3.jpg"},{"id":85845430,"identity":"b26570ae-2cc6-468f-bc3b-9280bb9269ad","added_by":"auto","created_at":"2025-07-02 09:38:23","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":38292,"visible":true,"origin":"","legend":"\u003cp\u003eHead circumference of the child (A) Before surgery, the head circumference measured 49.7 cm, (B) Three days post-operation, the head circumference decreased to 48.2 cm, and (C) two months post-operation, the head circumference remained at 48.2 cm.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780400/v1/e4333f57508ce8242e036216.jpg"},{"id":85844612,"identity":"012b069f-6487-4af5-b0d3-6a94ff1e4661","added_by":"auto","created_at":"2025-07-02 09:30:23","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":117389,"visible":true,"origin":"","legend":"\u003cp\u003eThe model of progression of intracranial tensional arachnoid cyst: (A) Early AC with the pressure in the AC cavity being lower than dynamic pulsatile ICP pressure; (B) Tension AC with a pressure balance between the inside and the outside of the AC; (C) After treatment, with the pressure in the cyst cavity being lower than the pressure around the cyst and the retraction of the cyst wall. a: Dynamic pulsatile ICP pressure; b: pressure of the surrounding tissue on the cyst; c: cyst wall tension; d: pressure of cyst cavity on cyst wall; e: pressure of cyst flow outlet. When a \u0026gt; d \u0026gt; b+c, the cyst enlarges; when a = d= b+c, the cyst remains stable; when a = (d-e) \u0026lt; b+c, the cyst shrinks; when a = d = e = b+c, the cyst becomes stable again.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780400/v1/36e4554a829fd7cc52f3dbac.jpg"},{"id":104251299,"identity":"dbf5d043-b52c-4aae-8ebe-8601d463a277","added_by":"auto","created_at":"2026-03-09 16:12:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":853460,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6780400/v1/726e1793-09f2-4da4-bc33-e216e5f895e6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Observation of the the progression of tension in intracranial arachnoid cyst: A case report and review of literature","fulltext":[{"header":"Introduction","content":"\u003cp\u003eArachnoid cysts (ACs) are common benign intracranial space-occupying lesions in children. They are pouch-like intra-arachnoid masses containing cerebrospinal fluid (CSF), primarily located in the CSF cisterna and the main cerebral fissure. Intracranial arachnoid cysts (IACs) constitute 1% of intracranial space-occupying lesions and affect 2.6% of the population under 18 years of age, with greater than 90% being asymptomatic\u003csup\u003e[\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e–\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIt is believed that congenital ACs may form in the early stages of subarachnoid space development, stemming from abnormal arachnoid replication and division during the embryonic period, and are associated with irregular CSF flow\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. The majority of congenital ACs are clinically silent and remain static in size; however, some IACs may gradually increase in size. Presently, research data from different centers indicate a wide variation in the proportion of enlarged IACs within the total IAC population, ranging from 0.73–19.7%\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e–\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Among 488 cases, only three demonstrated an increase during follow-up, clinically, changes in the size of IACs were rarely observed, with the majority remaining stable\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Yin et al.\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e reported on 60 cases of fetal IACs using conventional ultrasound, with thirty cases first detected during the second trimester and the remaining thirty during the third trimester. Ultrasound and magnetic resonance imaging (MRI) follow-ups revealed that IACs increased in 20% of cases, remained stable in 65%, and decreased in 15%. Another study\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e reported on the follow-up of 86 cases of IACs in children under the age of 5, with 17 cases showing enlargement. Among them, 11 cases enlarged without requiring surgery, 6 cases did not continuously enlarge, and 3 cases reduced in size. Al-Holou et al. \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e conducted a follow-up on 203 adult cases of IACs and found that IACs enlarged in 2.3% (5 cases), decreased in 0.9% (2 cases), and aggravated in only 0.9% (2 cases). These suggested that enlargement of IAC in adults is rare and should be distinguished from that in children, especially those under the age of 3. Although most IACs remain static throughout their lifespan, some ACs may enlarge under pressure, exerting a space-occupying effect on adjacent neural structures\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Among these cases, age stands out as the sole definitive effective factor.\u003c/p\u003e \u003cp\u003eBased on imaging features ACs were divided into tensional and non-tensional cysts\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. This classification system focuses on the role of tension in cyst enlargement and determining the appropriate time for surgical intervention. Nevertheless, due to the inability to clinically observe the progression of tension, the relationship between tension in cyst and cyst enlargement is currently unclear.\u003c/p\u003e \u003cp\u003eThe key words \"growing\", \"Space-Occupying\", \"Increasing Arachnoid Cysts\", \"Increasing Arachnoid Cyst\", \"Cystic Lesions\" was searched in PubMed and Web of Science for English literature. The starting point of search for English databases was unrestricted and ended in February 2024. Two independent reviewers searched and screened the relevant literature abstracts, and then the relevant studies were reviewed in full text and the data were extracted and checked. Out of the 15 articles reviewed, only 7 were considered eligible for inclusion as they discussed the relationship between tension in cyst and cyst enlargement of Acs\u003csup\u003e[\u003cspan additionalcitationids=\"CR11 CR12 CR13 CR14 CR15\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e–\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e, the remaining 8 articles mentioned tension but did not explore the relationship between tension in cysts and cyst enlargement of ACs, so they were excluded. (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Of the 7 articles, only 1 reported on hydrocephalus because of a voluminous left frontotemporal cyst with an important mass effect on the midline and lateral ventricles\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e, but none of which demonstrated the whole process.\u003c/p\u003e \u003cp\u003eIn this report, we presented a case of a small non-tension AC at the left cerebellopontine angle detected at birth. This cyst gradually developed into a giant tension AC, and subsequently shrank after AC cystostomy.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\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\u003eSummary of cases of tensional arachnoid cyst.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRef.\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eauthor\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eyear\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eage\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003esymptoms\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003elesion\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003epathogenesis\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\u003eTahir MZ\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e60y\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eheadaches, vomiting, seizures and altered state of consciousness\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003euncal herniation\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\u003eGraillon T\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e81y\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eprogressive hemiplegia and aphasia\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ehydrocephalus\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\u003eGadoth N\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1m\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eleft tonic conjugate gaze deviation\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003efalcial herniation\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\u003eBhattarai HB\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e35y\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003esudden loss of consciousness, anisocoria, and right hemiparesis\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003euncal herniation\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\u003eBalani A\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e70y\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eheadaches, vomiting and seizures followed by sudden onset loss of consciousness\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003euncal herniation\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\u003ePeng P\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e67y\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003edizziness, left lower limb numbness\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRT\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ecompression\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\u003eKaraaslan B\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1m\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eperipheral facial palsy\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRCPA\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ecompression\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003eLT: left temporal; RT: right temporal; RCPA: right cerebellopontine angle\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e"},{"header":"Case presentation","content":"\u003cp\u003eA 15-month-old child was admitted to the hospital due to a progressive increase in head circumference over the past year. Brain MRI performed 6 days after birth revealed a small AC in the left pontocerebellar region, without obstructive hydrocephalus at that time (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). At the age of 15 months, the child exhibited a progressive increase in head circumference, measuring 49.7 cm. Physical examination revealed retarded development, an abnormal head shape with a dilated and unclosed anterior fontanelle, measuring about 5*5 cm, and an inability to walk. Brain MRI showed a giant subarachnoid AC in the left pontocerebellar region, constricting the brain stem and left cerebellum. At the same time, CSF film demonstrated a weak CSF flow velocity signal in the midbrain aqueduct, accompanied by ventricle and fontanelle enlargement (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Due to the obstructive hydrocephalus caused by the AC, AC fenestration was performed under general anesthesia on July 12, 2023. During the operation, upon opening the dura mater, the AC wall exhibited high tension (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Upon piercing the AC wall, colorless clear liquid was ejected. Following the slow release of CSF, the AC wall collapsed. Upon full opening of the lateral AC wall, the AC wall of the cerebellum and the inner side of the brain stem appeared to bulge outward. Recognizing the reduced pressure in the AC cavity after opening, CSF accumulated outside the AC wall, forming an inverse bulge into the AC like a unidirectional valve (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB).\u003c/p\u003e\u003cp\u003eTo establish communication with the cisterna ambiens, the walls of the AC were further opened at the medial and ventral parts of the cerebellar brainstem (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). Brain MRI 2 months after the operation indicated a reduction in the AC cavity, alleviation of the mass effect, and a significant decrease in the child's head circumference (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eG, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eH, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eI, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eBased on imaging features AC were divided into tensional and non-tensional cysts\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. This classification system focuses on the role of tension in cyst enlargement and determining the appropriate time for surgical intervention. This case report clearly illustrates the relationship between tension in cyst and cyst enlargement.\u003c/p\u003e \u003cp\u003eAlthough the mechanism driving ACs enlargement remains unclear, several postulated mechanisms include: (1) The ball valve hypothesis: There may be an anatomic communication that acts functionally as a one-way valve between the cyst and the subarachnoid space. (2) Osmotic gradient between cystic content and cerebro-spinal fluid: This theory is not supported by evidence because the cystic content is similar in composition to CSF. Congenital arachnoid cysts are maldevelopmental anomalies and contain clear CSF-like fluid. In acquired cysts the intracystic fluid may be hemosiderin-stained or may contain inflammatory cells with a possible gradient. (3) Fluid production by the cells lining the walls of the cysts: There is some morphologic and ultracytochemical evidence to support the secretory nature of the cyst wall. The argument against continuous secretion is that the cysts often remain static in size and sometimes disappear, thus demonstrating that secretion is neither universal nor, likely, the only mechanism involved\u003csup\u003e[\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. Generally, if an AC enlarges, it can induce symptoms such as raised intracranial pressure, nausea and vomiting, focal neurologic deficits, or hydrocephalus\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Surgical intervention is typically recommended for symptomatic patients, depending on the AC effect, often determined by the tension of the AC. However, due to the infrequent observation of the progression of intracranial tensional AC, controversies persist regarding when and how to perform surgery. In this case, we posit that tension in the AC results from its progression and is associated with a unidirectional valve within the subarachnoid space.\u003c/p\u003e \u003cp\u003eSpeculatly, a small section of the AC wall forms a one-way valve. When intracranial pressure increases, which may caused by crying, exertion, or the Valsalva maneuver, the responsiveness of the subarachnoid space to changes in venous pressure might also lead to increased filling of the cysts and contribute to enlargement, preventing its outward flow due to the valve's unidirectional nature (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). Additionally, the brain tissue outside the cyst exerts pressure on the AC wall, which results in a pressure balance between the inside and outside of the AC, ultimately forming a stable tensional cyst (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). Consequently, IACs are often incidentally diagnosed during brain computed tomography or MRI scans conducted for unrelated symptoms. The stable appearance of the AC on imaging suggests a progression to a balanced state of both internal and external pressures within the AC. In the case of slit valves, pulsations of CSF flowing from caudad to cephalad in the prepontine cistern during the cardiac cycle lifted the wall of these cysts, increasing the opening of the slit valve and resulted in net flow of CSF into the cyst. Normal backflow of CSF into the spinal compartment is relatively blocked during the cardiac cycle, due to apposition of the slit valve against the tension exerted by the cyst way and adjacent brain tissue. Thus, this imbalance in oscillatory flow of CSF between the craniospinal compartments further supports the slit valve as being responsible for the increase in size of suprasellar prepontine arachnoid cysts.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eClinical data showed that tensional AC tend to become smaller after fenestration or shunt surgery, leading to the alleviation of corresponding clinical symptoms. If there is bidirectional communication in the AC, it should present non-tension characteristics, whereas the presence of a one-way valve would lead to gradual enlargement in the early stage, demonstrating tensional changes. Studies have demonstrated the existence of only a few small capillaries on the AC wall, lacking cells capable of clear fluid secretion. Moreover, the properties of AC cavity fluid and CSF proteins are roughly similar\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. Additionally, the majority of ACs do not increase in size. Therefore, we consider the mechanisms of gradual AC enlargement caused by fluid secretion from the AC wall or gradient differences to be unlikely. Under normal circumstances, high-pressure liquid will flow to a low-pressure area. Following the principles of mechanics, generally enlarged ACs are considered tension cysts.\u003c/p\u003e \u003cp\u003eThe primary surgical methods for AC intervention include craniotomy with cyst wall resection or AC fenestration, endoscopic cystocisternostomy, and cyst-peritoneal shunt (CPS) \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. A recent meta-analysis revealed no significant difference in the impact of these surgical methods on the quality of life of patients after 5 years\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. However, there were variations in efficacy among the three surgical methods. The reduction rate of ACs after craniotomy was 92%, with a near-total disappearance rate of 51%. For endoscopic fenestration, the reduction rate was 75%, and the near-total disappearance rate was 39%. CPS demonstrated the highest reduction rate of 100%, with a near-total disappearance rate of 89%\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. In terms of cyst disappearance and reduction rates, CPS exhibited the most favorable outcomes. However, serious complications, such as shunt dependency syndrome (SDS), can occur after CPS\u003csup\u003e[\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e. Shim et al.\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e reported that among 19 patients undergoing CPS, 8 developed SDS, with an average onset time of 6.1 years post-operation, reaching a proportion as high as 42%. In 11 cases with a complete disappearance of the cyst, attempting shunt removal by ligation was successful in 8 cases. Ventriculoperitoneal shunt not only effectively alleviates SDS through the reconstruction of the CSF circulation pathway but also prevents the enlarged cysts from increasing in size simultaneously. These conditions further suggest that the cyst fluid primarily originates from extracapsular CSF through a one-directional pathway, contradicting the theories of intracystic fluid production by secreting cells or fluid movement following an osmotic gradient. Therefore, ACs can be comprehended as a special type of hydrocephalus- local hydrocephalus.\u003c/p\u003e \u003cp\u003eIn this case, the cyst cavity gradually reduced in size and exhibited non-tensional changes after the subarachnoid fistula of the cyst (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC). This reduction was attributed to the pressure within the AC cavity being lower than the pressure surrounding the AC, leading to the retraction of the AC wall. Consequently, this case indirectly suggested that non-tensional ACs may not necessitate surgical intervention. Patients with SDS or slit-like ventricles after CPS pose significant treatment challenges. Therefore, the optimal approach is to restore the physiological flow of CSF in the capsule.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe AC is characterized by an abnormal accumulation of CSF in the CSF circulation pathway, akin to a localized hydrocephalus. The tensional features observed in AC imaging reflect the progression of the cyst. The severity of tension serves as the basis for surgical intervention and a critical index for assessing postoperative efficacy. The optimal treatment is arachnoid cystostomy, a procedure that not only restores the physiological flow and circulation of CSF within the capsule but also addresses the space-occupying effect of the AC, thereby avoiding the development of long-term SDS.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003earachnoid cyst\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCPS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ecyst-peritoneal shunt\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCSF\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ecerebrospinal fluid\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIACs\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eintracranial arachnoid cysts\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003emagnetic resonance imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSACs\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003espinal arachnoid cysts\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSDS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eshunt dependency syndrome.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate：Ethical approval was granted by the Ethics Committee of Fujian Sanbo Funeng Brain Hospital (No. FJSBNK-YJ-2025-002-01). Patients provided signed informed consent to participate in the study.\u003c/p\u003e\n\u003cp\u003eConsent for publication：Informed consent for publication of clinical details and/or clinical images was obtained from the parents of the patient.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials：The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003eCompeting Interests：The authors report no conflict of interest.\u003c/p\u003e\n\u003cp\u003eFunding：None.\u003c/p\u003e\n\u003cp\u003eAuthor Contribution：ZX. L,\u0026nbsp;JT. C, HR. D,\u0026nbsp;B.\u0026nbsp;L: conception and design, acquisition of data, analysis and interpretation of data, drafting of the article, and critically revising the article; Reviewed submitted version of the manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: ZX. L.\u003c/p\u003e\n\u003cp\u003eAcknowledgments：None.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSarwar S, Rocker J. Arachnoid cysts in paediatrics. Curr Opin Pediatr 2023, 35, 288-295. http://doi.org/10.1097/MOP.0000000000001219.\u003c/li\u003e\n\u003cli\u003eCarbone J, Sadasivan AP. Intracranial arachnoid cysts: Review of natural history and proposed treatment algorithm. Surg Neurol Int 2021, 12, 621. http://doi.org/10.25259/SNI_946_2021.\u003c/li\u003e\n\u003cli\u003eMustansir F, Bashir S, Darbar A. Management of Arachnoid Cysts: A Comprehensive Review. Cureus 2018, 10, e2458. http://doi.org/10.7759/cureus.2458.\u003c/li\u003e\n\u003cli\u003eRengachary SS, Watanabe I. Ultrastructure and pathogenesis of intracranial arachnoid cysts. J Neuropathol Exp Neurol 1981, 40, 61-83.\u003c/li\u003e\n\u003cli\u003eHuang JH, Mei WZ, Chen Y, Chen JW, Lin ZX. Analysis on clinical characteristics of intracranial Arachnoid Cysts in 488 pediatric cases. 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Expansion of arachnoid cysts in children: report of two cases and review of the literature. J Neurosurg 2005, 102, 314-317. http://doi.org/10.3171/ped.2005.102.3.0314.\u003c/li\u003e\n\u003cli\u003eDeopujari CE, Shaikh ST, Karmarkar VS, Sudke AY, Mohanty CB, Biyani NK. Experience with Management of Intracranial Arachnoid Cysts. J Neurol Surg A Cent Eur Neurosurg 2021, 82, 43-52. http://doi.org/10.1055/s-0040-1718522.\u003c/li\u003e\n\u003cli\u003eBerle M, Kroksveen AC, Haaland OA, Aye TT, Opsahl JA, Oveland E et al. Protein profiling reveals inter-individual protein homogeneity of arachnoid cyst fluid and high qualitative similarity to cerebrospinal fluid. Fluids Barriers CNS 2011, 8, 19. http://doi.org/10.1186/2045-8118-8-19.\u003c/li\u003e\n\u003cli\u003eBerle M, Kroksveen AC, Garberg H, Aarhus M, Haaland OA, Wester K et al. Quantitative proteomics comparison of arachnoid cyst fluid and cerebrospinal fluid collected perioperatively from arachnoid cyst patients. Fluids Barriers CNS 2013, 10, 17. http://doi.org/10.1186/2045-8118-10-17.\u003c/li\u003e\n\u003cli\u003eEl Refaee E, Elbaroody M. Endoscopic Fenestration of Arachnoid Cysts Through Lateral Pontomesencephalic Membranotomy: Technical Note and Case Series. World Neurosurg 2021, 148, 54-64. http://doi.org/10.1016/j.wneu.2020.12.108.\u003c/li\u003e\n\u003cli\u003eAli ZS, Lang SS, Bakar D, Storm PB, Stein SC. Pediatric intracranial arachnoid cysts: comparative effectiveness of surgical treatment options. Childs Nerv Syst 2014, 30, 461-469. http://doi.org/10.1007/s00381-013-2306-2.\u003c/li\u003e\n\u003cli\u003eTamburrini G, Dal Fabbro M, Di Rocco C. Sylvian fissure arachnoid cysts: a survey on their diagnostic workout and practical management. Childs Nerv Syst 2008, 24, 593-604. http://doi.org/10.1007/s00381-008-0585-9.\u003c/li\u003e\n\u003cli\u003eLi C, Yin L, Jiang T, Ma Z, Jia G. Shunt dependency syndrome after cystoperitoneal shunting of arachnoid cysts. Childs Nerv Syst 2014, 30, 471-476. http://doi.org/10.1007/s00381-013-2248-8.\u003c/li\u003e\n\u003cli\u003eMerola J, Manivannan S, Ooi S, Li Chia W, Makwana M, Lang J et al. The efficacy of cystoperitoneal shunting for the surgical management of intracranial arachnoid cysts in the elderly: A systematic review of the literature. Surg Neurol Int 2021, 12, 624. http://doi.org/10.25259/SNI_463_2021.\u003c/li\u003e\n\u003cli\u003eZhang B, Zhang Y, Ma Z. Long-term results of cystoperitoneal shunt placement for the treatment of arachnoid cysts in children. J Neurosurg Pediatr 2012, 10, 302-305. http://doi.org/10.3171/2012.7.PEDS11540.\u003c/li\u003e\n\u003cli\u003eShim KW, Lee YH, Park EK, Park YS, Choi JU, Kim DS. Treatment option for arachnoid cysts. Childs Nerv Syst 2009, 25, 1459-1466. http://doi.org/10.1007/s00381-009-0930-7.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bped","sideBox":"Learn more about [BMC Pediatrics](http://bmcpediatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bped/default.aspx","title":"BMC Pediatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Arachnoid cyst, “Ball-valve” mechanism, Congenital benign cysts, Endoscopic fenestration, case report","lastPublishedDoi":"10.21203/rs.3.rs-6780400/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6780400/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eArachnoid cysts (ACs) are common benign intracranial space-occupying lesions in children can be categorized into tensional and non-tensional cysts based on imaging features. The majority of ACs are clinically silent and remain static in size; however, some intracranial ACs may gradually increase in size. However, the relationship between tension in cyst and cyst enlargement is currently unclear. Due to the rarity of observed progression of tension in intracranial ACs, controversies persist regarding when and how to perform surgery. We present a rare case of a progressive increase in head circumference over one year in a 15-month-old child caused by growing tensional AC at the left cerebellopontine angle. Brain magnetic resonance imaging (MRI) at 6 days after birth revealed a small non-tension AC at the left cerebellopontine angle with no apparent compression of adjacent brain tissue and clear sulci and gyri. At 15 months, the MRI revealed a significant enlargement of AC, brain stem was displaced, sulci of the adjacent brain tissue disappeared, and the cyst-brain tissue interface displayed a tensional arc-type change, accompanied by obstructive hydrocephalus. Through fenestration, the AC was reduced, exhibiting non-tension changes, significantly alleviating pressure on adjacent brain tissue, and hydrocephalus significantly improved. Subsequent follow-ups showed no obvious abnormalities.\u003c/p\u003e \u003cp\u003eIn conclusion, the degree of tension seen in AC imaging is the result of cyst enlargement, guiding surgical intervention and postoperative efficacy evaluation.\u003c/p\u003e","manuscriptTitle":"Observation of the the progression of tension in intracranial arachnoid cyst: A case report and review of literature","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-02 09:22:18","doi":"10.21203/rs.3.rs-6780400/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-01T06:58:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-20T02:14:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-12T07:08:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"89464161837143905062137352613003716652","date":"2025-07-11T03:49:27+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-10T16:32:52+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-09T08:26:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"139012508206457156418477261180391945115","date":"2025-07-03T01:30:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"123167062060939947314381316574705140350","date":"2025-07-02T10:28:56+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-29T13:51:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"331234596905246651617504672231805845786","date":"2025-06-26T18:14:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"328747183833977579414338615894835438799","date":"2025-06-25T08:44:55+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-24T18:03:02+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-18T10:27:51+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-05-30T17:03:45+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-30T09:20:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pediatrics","date":"2025-05-30T09:17:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bped","sideBox":"Learn more about [BMC Pediatrics](http://bmcpediatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bped/default.aspx","title":"BMC Pediatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4aaae5d4-3341-4736-9d76-47648b917daf","owner":[],"postedDate":"July 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-09T16:09:26+00:00","versionOfRecord":{"articleIdentity":"rs-6780400","link":"https://doi.org/10.1186/s12887-026-06618-8","journal":{"identity":"bmc-pediatrics","isVorOnly":false,"title":"BMC Pediatrics"},"publishedOn":"2026-03-05 15:59:43","publishedOnDateReadable":"March 5th, 2026"},"versionCreatedAt":"2025-07-02 09:22:18","video":"","vorDoi":"10.1186/s12887-026-06618-8","vorDoiUrl":"https://doi.org/10.1186/s12887-026-06618-8","workflowStages":[]},"version":"v1","identity":"rs-6780400","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6780400","identity":"rs-6780400","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}