Thrombosed Pediatric Cerebral Arteriovenous Malformation Mimicking an Intraventricular Tumor: A Case Report

Thrombosed Pediatric Cerebral Arteriovenous Malformation Mimicking an Intraventricular Tumor: A Case Report | 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 Thrombosed Pediatric Cerebral Arteriovenous Malformation Mimicking an Intraventricular Tumor: A Case Report Felipe Chavelas-Ochoa, Ana Lucía Osejo-Cantarero, Miguel Isaías Paredes-Serrano, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8835757/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 Thrombosed cerebral arteriovenous malformations (AVMs) are rare entities in the pediatric population and may present significant diagnostic challenges. Thrombosis can alter the typical vascular imaging features of these lesions, leading to a loss of flow-related signs and causing them to mimic intracranial neoplasms. We report the case of a 13-year-old boy who presented with a first-onset generalized seizure and was found to have a large intraventricular mass initially suspected to be a tumor based on neuroimaging findings. Magnetic resonance imaging demonstrated a bilobed intraventricular lesion with heterogeneous signal intensity, minimal contrast enhancement, absence of flow voids, and small cystic degenerative areas. Given the diagnostic uncertainty and the presence of focal neurological deficits, microsurgical resection was performed. Histopathological examination revealed a thrombosed AVM without neoplastic features. This case highlights the importance of considering thrombosed AVMs in the differential diagnosis of intraventricular masses in children, even in the absence of classic vascular imaging characteristics. Arteriovenous malformations Thrombosis Pediatrics Intraventricular lesions Figures Figure 1 Figure 2 Figure 3 Figure 4 INTRODUCTION Cerebral arteriovenous malformations (AVMs) are congenital vascular anomalies that may present with hemorrhage, seizures, or focal neurological deficits in the pediatric population [ 3 , 8 ]. Although their radiological appearance is usually characteristic, spontaneous thrombosis of the nidus is uncommon. This process may substantially alter both the clinical presentation and imaging findings [ 6 , 7 ]. When thrombosis occurs, typical vascular hallmarks such as flow voids, early venous drainage, and marked contrast enhancement may be absent, resembling solid neoplastic processes [ 3 , 6 ]. Intraventricular location is particularly rare and further contributes to diagnostic uncertainty [ 9 , 1 ]. Intraventricular AVMs account for only a small fraction of cerebral AVMs and are most often associated with hemorrhage or hydrocephalus; however, they may occasionally present as tumor-like lesions with negative or inconclusive angiographic findings, especially in the presence of thrombosis or chronic degenerative changes [ 9 , 12 ]. This atypical presentation increases the risk of misdiagnosis and may influence surgical decision-making. We report a pediatric case of a thrombosed cerebral arteriovenous malformation presenting as an intraventricular mass initially suspected to be a tumor, emphasizing the importance of considering thrombosed vascular lesions in the differential diagnosis of ventricular masses in children. CASE REPORT A 13-year-old boy with no relevant past medical history was evaluated. He was born after an uncomplicated pregnancy with adequate prenatal care and normal obstetric ultrasounds, and his perinatal and postnatal development were unremarkable. According to his parents, he had experienced persistent reading difficulties since early childhood, without prior neurological assessment. There was no history of seizures, headache, head trauma, or central nervous system infection. The patient was admitted after presenting a first-onset generalized tonic–clonic seizure without sphincter relaxation in the early morning hours. Initial evaluation at a primary care center included a non-contrast brain computed tomography scan, which revealed a hyperdense space-occupying lesion in the right temporoparietal region, measuring approximately 4 × 5.5 × 4.5 cm, prompting referral for specialized neurosurgical management. On admission, neurological examination demonstrated a Glasgow Coma Scale score of 14, mild deviation of the labial commissure, and left-sided hemiparesis with muscle strength graded at 3/5. No clinical signs of increased intracranial pressure were observed. Contrast-enhanced brain magnetic resonance imaging revealed an intraventricular mass involving the atrium and occipital recess of the right lateral ventricle, with heterogeneous signal characteristics, minimal contrast enhancement, and absence of flow-related vascular features. No associated hydrocephalus or significant perilesional edema was identified. Based on these findings, an intraventricular neoplastic process was initially suspected (Fig. 1). Magnetic resonance spectroscopy demonstrated metabolic alterations characterized by a glutamate–glutamine complex peak, consistent with chronic hypoxic-ischemic-related metabolic changes within the lesion (Fig. 2). Given the lesion size, the presence of focal neurological deficit, and the persistent diagnostic uncertainty, surgical treatment was indicated. The patient underwent microsurgical excision of the lesion without intraoperative complications. Postoperative recovery was uneventful, and the patient was discharged without new neurological deficits. At three-month follow-up, neurological examination was normal. Postoperative contrast-enhanced computed tomography confirmed complete lesion removal with no residual enhancement (Fig. 3). Histopathological analysis revealed a vascular lesion composed of dilated and congested anastomosing vessels with multiple foci of recent and old thrombosis and partial recanalization. No evidence of neoplastic tissue was identified, establishing the diagnosis of a thrombosed cerebral AVM (Fig. 4). DISCUSSION AND CONCLUSION Spontaneous thrombosis of cerebral arteriovenous malformations (AVMs) is an uncommon phenomenon, reported in fewer than 1–1.5% of cases, with an even lower frequency in the pediatric population [ 3 , 7 , 11 ]. Similar cases of spontaneous thrombosis, including venous outflow occlusion and long-term radiological follow-up, have been described in both adult and pediatric populations [ 2 , 4 , 5 ]. Histopathological studies have shown that thrombosed AVMs may undergo progressive vascular fibrosis, luminal occlusion, and chronic degenerative changes, leading to loss of their typical vascular architecture [ 10 ]. Therefore, these lesions may present as solid mass-like entities and pose significant diagnostic challenges. Radiologically, thrombosed AVMs often lack classic vascular hallmarks such as flow voids, prominent vascular structures, or avid contrast enhancement. Mitnick et al. described a pediatric series in which thrombosed AVMs frequently appeared as lobulated, minimally enhancing lesions with little or no surrounding edema and negative angiography, leading to frequent misdiagnosis as low-grade neoplasms [ 6 ]. These findings explain why thrombosed AVMs may be indistinguishable from tumors on conventional imaging, particularly when hemorrhage is absent. Intraventricular AVMs are exceptionally rare and are most often associated with intraventricular hemorrhage or hydrocephalus [ 9 , 12 ]. Several reports have emphasized that intraventricular vascular malformations may closely mimic primary ventricular tumors when typical vascular characteristics are not evident on imaging [ 9 , 1 ]. However, most published cases describe hemorrhagic presentations or hydrocephalus, whereas non-hemorrhagic, tumor-like presentations remain exceedingly uncommon. The present case shares the diagnostic ambiguity described in prior reports of intraventricular AVMs but differs in its predominantly thrombosed nature, absence of acute hemorrhage or hydrocephalus, and indolent clinical course. Extensive thrombosis with associated degenerative changes likely accounts for the absence of overt vascular imaging features and the misleading tumor-like appearance. In addition, metabolic alterations observed on magnetic resonance spectroscopy supported chronic intralesional ischemic and hypoxic changes, a feature rarely documented in prior reports. This case underscores the importance of including thrombosed vascular malformations in the differential diagnosis of intraventricular masses in children. Awareness of this rare presentation is essential to avoid misdiagnosis, anticipate intraoperative bleeding risk, and guide appropriate surgical planning and management. Declarations Competing Interests The authors declare that they have no competing interests. Funding The authors received no specific funding for this work. Ethical approval and consent to participate Written informed consent for publication of clinical data and images was obtained from the patient’s legal guardian. Consent for publication Written informed consent for publication was obtained from the patient’s legal guardian. Author Contribution F.C.O. was the treating neurosurgeon and primary responsible clinician for the case, and performed the final critical review of the manuscript.M.A.S.L. wrote the final version of the manuscript, performed the literature review, and coordinated the overall revision process.A.L.O.C. and C.G.J.O.P. contributed to the initial drafting of the manuscript and data collection.M.I.P.S. performed the histopathological analysis and provided the pathological interpretation.All authors reviewed and approved the final manuscript and agree to be accountable for all aspects of the work. Data Availability All data supporting the findings of this study are included within the article. References Bhaskar MK, Jaiswal M, Ojha BK, Meel M, Singh AK, Mishra M (2017) Intraventricular arteriovenous malformation mimicking tumor: a rare presentation. Int J Neurol Neurosurg 9:57–59. https://doi.org/10.21088/ijnns.0975.0223.9117.11 Cao C, Sourour N, Reina V, Nouet A, Di Maria F, Chiras J, Cornu P, Clarençon F (2015) Spontaneous thrombosis of the main draining vein revealing an unruptured brain arteriovenous malformation. Interv Neuroradiol 21:222–226. https://doi.org/10.1177/1591019915581989 Dyck P (1977) Spontaneous thrombosis of an arteriovenous malformation. Neurosurgery 1(3):287–290. Iampreechakul P, Wangtanaphat K, Wattanasen Y, Hangsapruek S, Lertbutsayanukul P, Siriwimonmas S. Long-term surveillance in an infant with spontaneous obliteration of pial arteriovenous malformation and large intranidal aneurysm: A unique case observation. Surg Neurol Int. 2024;15:206. doi:10.25259/SNI_45_2024 Milazzo N, Pizzuto S, Gratieux J, Sgreccia A, Di Maria F, Coskun O, Condette-Auliac S, Boulin A, Rodesch G, Consoli A (2024) A case of spontaneous brain arteriovenous malformation occlusion: imaging analysis and clinical debate. Interventional Neuroradiology . https://doi.org/10.1177/15910199231226142 Mitnick JS, Pinto RS, Lin JP, Rose H, Lieberman A (1984) CT of thrombosed arteriovenous malformations in children. Radiology 150:385–389. Panagopoulos D, Markogiannakis G, Themistocleous M (2020) Ruptured arteriovenous malformation anterior to the brainstem to a child with subsequent spontaneous thrombosis: Case report and literature review. Am J Case Rep 21:e923289. https://doi.org/10.12659/AJCR.923289 See AP, Smith ER. Management of pediatric intracranial arteriovenous malformations. J Korean Neurosurg Soc. 2024;67(3):289–298. doi:10.3340/jkns.2024.0027 Song WZ, Mao BY, Hu BF, Liu YH, Sun H, Mao Q (2008) Intraventricular vascular malformations mimicking tumors: case reports and review of the literature. J Neurol Sci 266:63–69. https://doi.org/10.1016/j.jns.2007.08.045 Takashima S, Becker LE (1980) Neuropathology of cerebral arteriovenous malformations in children. Journal of Neurology, Neurosurgery, and Psychiatry 43:380–385. https://doi.org/10.1136/jnnp.43.5.380 Ulumuddin MI, Sani AF, Kurniawan D (2023) Spontaneous thrombosis of deep brain arteriovenous malformation in a patient with intraventricular and subarachnoid hemorrhage. Radiol Case Rep 18(8):3620–3625. https://doi.org/10.1016/j.radcr.2023.07.040 Zhao P, Maragkos GA, Livingstone KS, Kearns KN, Park MS (2023) Choroid plexus arteriovenous malformations: A systematic review. J Cerebrovasc Endovasc Neurosurg 25:373–379. https://doi.org/10.7461/jcen.2023.E2023.02.002 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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-8835757","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":609438266,"identity":"804c1171-8c8e-41e7-a2f5-871e08886a34","order_by":0,"name":"Felipe Chavelas-Ochoa","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIiWNgGAWjYPCCA0DM3MDAUAGiQQzitDACVZ4BaWEkRQtjGwNULx5gzt5j9uFDzR15g+ONjR9/zquN5m8HavlRsQ2nFsueM8YzZxx7ZrjhzMFmad5tx3NnHGZsYOw5cxunFoMbOcbMvA2HGWfOSGyQZtx2LBfIbmBmbMOj5f4bsBb7mfMfNv/8OedY7nyCWm7wgLUk9kswtknwNtTkbiCo5UxaMeOMY4eT+3kS26x5jh3I3QjUchCvX44f3szwoeawbRv74cM3f9TU5c47f/jggx8VuLWgg8Ng8gDR6oGgjhTFo2AUjIJRMEIAAINHYa0L41HfAAAAAElFTkSuQmCC","orcid":"","institution":"Hospital de Especialidades del Niño y la Mujer","correspondingAuthor":true,"prefix":"","firstName":"Felipe","middleName":"","lastName":"Chavelas-Ochoa","suffix":""},{"id":609438267,"identity":"41788db6-0731-46d2-9ef9-f1b41415825f","order_by":1,"name":"Ana Lucía Osejo-Cantarero","email":"","orcid":"","institution":"Hospital César Amador Molina","correspondingAuthor":false,"prefix":"","firstName":"Ana","middleName":"Lucía","lastName":"Osejo-Cantarero","suffix":""},{"id":609438268,"identity":"8d997110-a387-4d10-b2d3-83c9ff31532f","order_by":2,"name":"Miguel Isaías Paredes-Serrano","email":"","orcid":"","institution":"Biopath Laboratories","correspondingAuthor":false,"prefix":"","firstName":"Miguel","middleName":"Isaías","lastName":"Paredes-Serrano","suffix":""},{"id":609438269,"identity":"850c5981-f219-4d5e-8448-c814725cbd2c","order_by":3,"name":"Christian Gabriel Jesús Ordaz-Pérez","email":"","orcid":"","institution":"Hospital Civil de Guadalajara “Dr. Juan I. Menchaca”","correspondingAuthor":false,"prefix":"","firstName":"Christian","middleName":"Gabriel Jesús","lastName":"Ordaz-Pérez","suffix":""},{"id":609438270,"identity":"907f80eb-441e-4248-855a-5cf322f16554","order_by":4,"name":"Miguel Angel Solís-Lecuona","email":"","orcid":"","institution":"Hospital de Especialidades Médicas de la Salud","correspondingAuthor":false,"prefix":"","firstName":"Miguel","middleName":"Angel","lastName":"Solís-Lecuona","suffix":""}],"badges":[],"createdAt":"2026-02-10 03:10:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8835757/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8835757/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105409875,"identity":"a3019a90-8cdf-4651-9459-a17d21913e86","added_by":"auto","created_at":"2026-03-25 17:11:04","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":810811,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePreoperative brain magnetic resonance imaging.\u003c/strong\u003e (a) Sagittal T1-weighted image showing an irregular, lobulated intraventricular lesion centered in the atrium and occipital horn of the right lateral ventricle, with heterogeneous signal intensity and internal hyperintense cystic components. (b) Axial T2-weighted image showing a predominantly isointense and heterogeneous lesion, with few surrounding hyperintensity suggestive of perilesional edema. (c) Coronal contrast-enhanced T1-weighted image showing mild and heterogeneous enhancement, with central areas of relatively decreased enhancement, and absence of identifiable flow voids or associated hydrocephalus.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8835757/v1/a08da9c0629c8ff29ccd5587.png"},{"id":105409800,"identity":"aa8d2d5c-865a-4a93-bac9-d616ce457a67","added_by":"auto","created_at":"2026-03-25 17:10:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":572629,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePreoperative magnetic resonance spectroscopy\u003c/strong\u003e obtained from the intraventricular lesion, demonstrating a prominent glutamate–glutamine (Glx) complex peak, with relative reduction of N-acetylaspartate.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8835757/v1/fb1fa77b6de19314c9364cf7.png"},{"id":105409799,"identity":"026c5e5e-3969-4d16-a961-96d56665d430","added_by":"auto","created_at":"2026-03-25 17:10:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":650147,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePostoperative contrast-enhanced brain computed tomography. \u003c/strong\u003e(a) Sagittal section showing postoperative changes in the region of the right lateral ventricle without residual mass.\u003cstrong\u003e \u003c/strong\u003e(b) Axial section demonstrating absence of residual lesion or abnormal contrast enhancement.\u003cstrong\u003e \u003c/strong\u003e(c) Coronal section confirming adequate excision of the intraventricular lesion, without evidence of hydrocephalus or postoperative complications.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8835757/v1/d071737fe352c68fbee15985.png"},{"id":105409806,"identity":"57a9ae46-f828-4639-899a-40288e9f4cdb","added_by":"auto","created_at":"2026-03-25 17:10:56","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1268114,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePathological findings.\u003c/strong\u003e (a) Macroscopic view of the surgical specimen showing multiple reddish-brown tissue fragments with elastic consistency, weighing 65 g and measuring 5.5 x 5 x 4.5 cm. (b) Histopathological examination (hematoxylin and eosin stain) demonstrating dilated and congested anastomosing vascular channels with areas of recent and old thrombosis, without evidence of neoplastic cells.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8835757/v1/bdea7bd384cd119519e02a19.png"},{"id":109092984,"identity":"ab70c187-3ae2-4cb0-8d0c-fbbba95bbb37","added_by":"auto","created_at":"2026-05-12 13:43:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4145582,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8835757/v1/d79c3c6a-578b-4c27-90eb-0887cef526e9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Thrombosed Pediatric Cerebral Arteriovenous Malformation Mimicking an Intraventricular Tumor: A Case Report","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eCerebral arteriovenous malformations (AVMs) are congenital vascular anomalies that may present with hemorrhage, seizures, or focal neurological deficits in the pediatric population [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Although their radiological appearance is usually characteristic, spontaneous thrombosis of the nidus is uncommon. This process may substantially alter both the clinical presentation and imaging findings [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWhen thrombosis occurs, typical vascular hallmarks such as flow voids, early venous drainage, and marked contrast enhancement may be absent, resembling solid neoplastic processes [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Intraventricular location is particularly rare and further contributes to diagnostic uncertainty [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIntraventricular AVMs account for only a small fraction of cerebral AVMs and are most often associated with hemorrhage or hydrocephalus; however, they may occasionally present as tumor-like lesions with negative or inconclusive angiographic findings, especially in the presence of thrombosis or chronic degenerative changes [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. This atypical presentation increases the risk of misdiagnosis and may influence surgical decision-making.\u003c/p\u003e \u003cp\u003eWe report a pediatric case of a thrombosed cerebral arteriovenous malformation presenting as an intraventricular mass initially suspected to be a tumor, emphasizing the importance of considering thrombosed vascular lesions in the differential diagnosis of ventricular masses in children.\u003c/p\u003e"},{"header":"CASE REPORT","content":"\u003cp\u003eA 13-year-old boy with no relevant past medical history was evaluated. He was born after an uncomplicated pregnancy with adequate prenatal care and normal obstetric ultrasounds, and his perinatal and postnatal development were unremarkable. According to his parents, he had experienced persistent reading difficulties since early childhood, without prior neurological assessment. There was no history of seizures, headache, head trauma, or central nervous system infection.\u003c/p\u003e\n\u003cp\u003eThe patient was admitted after presenting a first-onset generalized tonic\u0026ndash;clonic seizure without sphincter relaxation in the early morning hours. Initial evaluation at a primary care center included a non-contrast brain computed tomography scan, which revealed a hyperdense space-occupying lesion in the right temporoparietal region, measuring approximately 4 \u0026times; 5.5 \u0026times; 4.5 cm, prompting referral for specialized neurosurgical management.\u003c/p\u003e\n\u003cp\u003eOn admission, neurological examination demonstrated a Glasgow Coma Scale score of 14, mild deviation of the labial commissure, and left-sided hemiparesis with muscle strength graded at 3/5. No clinical signs of increased intracranial pressure were observed.\u003c/p\u003e\n\u003cp\u003eContrast-enhanced brain magnetic resonance imaging revealed an intraventricular mass involving the atrium and occipital recess of the right lateral ventricle, with heterogeneous signal characteristics, minimal contrast enhancement, and absence of flow-related vascular features. No associated hydrocephalus or significant perilesional edema was identified. Based on these findings, an intraventricular neoplastic process was initially suspected\u003cstrong\u003e\u0026nbsp;(Fig. 1).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMagnetic resonance spectroscopy demonstrated metabolic alterations characterized by a glutamate\u0026ndash;glutamine complex peak, consistent with chronic hypoxic-ischemic-related metabolic changes within the lesion \u003cstrong\u003e(Fig. 2).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGiven the lesion size, the presence of focal neurological deficit, and the persistent diagnostic uncertainty, surgical treatment was indicated. The patient underwent microsurgical excision of the lesion without intraoperative complications.\u003c/p\u003e\n\u003cp\u003ePostoperative recovery was uneventful, and the patient was discharged without new neurological deficits. At three-month follow-up, neurological examination was normal. Postoperative contrast-enhanced computed tomography confirmed complete lesion removal with no residual enhancement \u003cstrong\u003e(Fig. 3).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHistopathological analysis revealed a vascular lesion composed of dilated and congested anastomosing vessels with multiple foci of recent and old thrombosis and partial recanalization. No evidence of neoplastic tissue was identified, establishing the diagnosis of a thrombosed cerebral AVM \u003cstrong\u003e(Fig. 4).\u003c/strong\u003e\u003c/p\u003e"},{"header":"DISCUSSION AND CONCLUSION","content":"\u003cp\u003eSpontaneous thrombosis of cerebral arteriovenous malformations (AVMs) is an uncommon phenomenon, reported in fewer than 1–1.5% of cases, with an even lower frequency in the pediatric population [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. Similar cases of spontaneous thrombosis, including venous outflow occlusion and long-term radiological follow-up, have been described in both adult and pediatric populations [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e]. Histopathological studies have shown that thrombosed AVMs may undergo progressive vascular fibrosis, luminal occlusion, and chronic degenerative changes, leading to loss of their typical vascular architecture [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]. Therefore, these lesions may present as solid mass-like entities and pose significant diagnostic challenges.\u003c/p\u003e\u003cp\u003eRadiologically, thrombosed AVMs often lack classic vascular hallmarks such as flow voids, prominent vascular structures, or avid contrast enhancement. Mitnick et al. described a pediatric series in which thrombosed AVMs frequently appeared as lobulated, minimally enhancing lesions with little or no surrounding edema and negative angiography, leading to frequent misdiagnosis as low-grade neoplasms [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. These findings explain why thrombosed AVMs may be indistinguishable from tumors on conventional imaging, particularly when hemorrhage is absent.\u003c/p\u003e\u003cp\u003eIntraventricular AVMs are exceptionally rare and are most often associated with intraventricular hemorrhage or hydrocephalus [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]. Several reports have emphasized that intraventricular vascular malformations may closely mimic primary ventricular tumors when typical vascular characteristics are not evident on imaging [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e]. However, most published cases describe hemorrhagic presentations or hydrocephalus, whereas non-hemorrhagic, tumor-like presentations remain exceedingly uncommon.\u003c/p\u003e\u003cp\u003eThe present case shares the diagnostic ambiguity described in prior reports of intraventricular AVMs but differs in its predominantly thrombosed nature, absence of acute hemorrhage or hydrocephalus, and indolent clinical course. Extensive thrombosis with associated degenerative changes likely accounts for the absence of overt vascular imaging features and the misleading tumor-like appearance. In addition, metabolic alterations observed on magnetic resonance spectroscopy supported chronic intralesional ischemic and hypoxic changes, a feature rarely documented in prior reports.\u003c/p\u003e\u003cp\u003eThis case underscores the importance of including thrombosed vascular malformations in the differential diagnosis of intraventricular masses in children. Awareness of this rare presentation is essential to avoid misdiagnosis, anticipate intraoperative bleeding risk, and guide appropriate surgical planning and management.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting Interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThe authors received no specific funding for this work.\u003c/p\u003e\n\u003ch2\u003eEthical approval and consent to participate\u003c/h2\u003e\n\u003cp\u003eWritten informed consent for publication of clinical data and images was obtained from the patient\u0026rsquo;s legal guardian.\u003c/p\u003e\n\u003ch2\u003eConsent for publication\u003c/h2\u003e\n\u003cp\u003eWritten informed consent for publication was obtained from the patient\u0026rsquo;s legal guardian.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eF.C.O. was the treating neurosurgeon and primary responsible clinician for the case, and performed the final critical review of the manuscript.M.A.S.L. wrote the final version of the manuscript, performed the literature review, and coordinated the overall revision process.A.L.O.C. and C.G.J.O.P. contributed to the initial drafting of the manuscript and data collection.M.I.P.S. performed the histopathological analysis and provided the pathological interpretation.All authors reviewed and approved the final manuscript and agree to be accountable for all aspects of the work.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eAll data supporting the findings of this study are included within the article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBhaskar MK, Jaiswal M, Ojha BK, Meel M, Singh AK, Mishra M (2017) Intraventricular arteriovenous malformation mimicking tumor: a rare presentation. \u003cem\u003eInt J Neurol Neurosurg\u003c/em\u003e 9:57\u0026ndash;59. https://doi.org/10.21088/ijnns.0975.0223.9117.11\u003c/li\u003e\n\u003cli\u003eCao C, Sourour N, Reina V, Nouet A, Di Maria F, Chiras J, Cornu P, Clarençon F (2015) Spontaneous thrombosis of the main draining vein revealing an unruptured brain arteriovenous malformation. \u003cem\u003eInterv Neuroradiol\u003c/em\u003e 21:222\u0026ndash;226. https://doi.org/10.1177/1591019915581989\u003c/li\u003e\n\u003cli\u003eDyck P (1977) Spontaneous thrombosis of an arteriovenous malformation. \u003cem\u003eNeurosurgery\u003c/em\u003e 1(3):287\u0026ndash;290.\u003c/li\u003e\n\u003cli\u003eIampreechakul P, Wangtanaphat K, Wattanasen Y, Hangsapruek S, Lertbutsayanukul P, Siriwimonmas S. Long-term surveillance in an infant with spontaneous obliteration of pial arteriovenous malformation and large intranidal aneurysm: A unique case observation. Surg Neurol Int. 2024;15:206. doi:10.25259/SNI_45_2024\u003c/li\u003e\n\u003cli\u003eMilazzo N, Pizzuto S, Gratieux J, Sgreccia A, Di Maria F, Coskun O, Condette-Auliac S, Boulin A, Rodesch G, Consoli A (2024) A case of spontaneous brain arteriovenous malformation occlusion: imaging analysis and clinical debate. \u003cem\u003eInterventional Neuroradiology\u003c/em\u003e. https://doi.org/10.1177/15910199231226142\u003c/li\u003e\n\u003cli\u003eMitnick JS, Pinto RS, Lin JP, Rose H, Lieberman A (1984) CT of thrombosed arteriovenous malformations in children. \u003cem\u003eRadiology\u003c/em\u003e 150:385\u0026ndash;389.\u003c/li\u003e\n\u003cli\u003ePanagopoulos D, Markogiannakis G, Themistocleous M (2020) Ruptured arteriovenous malformation anterior to the brainstem to a child with subsequent spontaneous thrombosis: Case report and literature review. \u003cem\u003eAm J Case Rep\u003c/em\u003e 21:e923289. https://doi.org/10.12659/AJCR.923289\u003c/li\u003e\n\u003cli\u003eSee AP, Smith ER. Management of pediatric intracranial arteriovenous malformations. J Korean Neurosurg Soc. 2024;67(3):289\u0026ndash;298. doi:10.3340/jkns.2024.0027\u003c/li\u003e\n\u003cli\u003eSong WZ, Mao BY, Hu BF, Liu YH, Sun H, Mao Q (2008) Intraventricular vascular malformations mimicking tumors: case reports and review of the literature. \u003cem\u003eJ Neurol Sci\u003c/em\u003e 266:63\u0026ndash;69. https://doi.org/10.1016/j.jns.2007.08.045\u003c/li\u003e\n\u003cli\u003eTakashima S, Becker LE (1980) Neuropathology of cerebral arteriovenous malformations in children. \u003cem\u003eJournal of Neurology, Neurosurgery, and Psychiatry\u003c/em\u003e 43:380\u0026ndash;385. https://doi.org/10.1136/jnnp.43.5.380\u003c/li\u003e\n\u003cli\u003eUlumuddin MI, Sani AF, Kurniawan D (2023) Spontaneous thrombosis of deep brain arteriovenous malformation in a patient with intraventricular and subarachnoid hemorrhage. Radiol Case Rep 18(8):3620\u0026ndash;3625. https://doi.org/10.1016/j.radcr.2023.07.040\u003c/li\u003e\n\u003cli\u003eZhao P, Maragkos GA, Livingstone KS, Kearns KN, Park MS (2023) Choroid plexus arteriovenous malformations: A systematic review. J Cerebrovasc Endovasc Neurosurg 25:373\u0026ndash;379. https://doi.org/10.7461/jcen.2023.E2023.02.002\u003c/li\u003e\n\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":"Arteriovenous malformations, Thrombosis, Pediatrics, Intraventricular lesions","lastPublishedDoi":"10.21203/rs.3.rs-8835757/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8835757/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThrombosed cerebral arteriovenous malformations (AVMs) are rare entities in the pediatric population and may present significant diagnostic challenges. Thrombosis can alter the typical vascular imaging features of these lesions, leading to a loss of flow-related signs and causing them to mimic intracranial neoplasms. We report the case of a 13-year-old boy who presented with a first-onset generalized seizure and was found to have a large intraventricular mass initially suspected to be a tumor based on neuroimaging findings. Magnetic resonance imaging demonstrated a bilobed intraventricular lesion with heterogeneous signal intensity, minimal contrast enhancement, absence of flow voids, and small cystic degenerative areas. Given the diagnostic uncertainty and the presence of focal neurological deficits, microsurgical resection was performed. Histopathological examination revealed a thrombosed AVM without neoplastic features. This case highlights the importance of considering thrombosed AVMs in the differential diagnosis of intraventricular masses in children, even in the absence of classic vascular imaging characteristics.\u003c/p\u003e","manuscriptTitle":"Thrombosed Pediatric Cerebral Arteriovenous Malformation Mimicking an Intraventricular Tumor: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-25 17:09:38","doi":"10.21203/rs.3.rs-8835757/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":"5f94b050-b431-4803-b3ea-0d61dce5d244","owner":[],"postedDate":"March 25th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Rejected","date":"2026-05-12T11:34:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T15:22:22+00:00","index":19,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-12T13:07:05+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-25 17:09:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8835757","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8835757","identity":"rs-8835757","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}