Atypical Intra-diploic Epidermoid Cyst: A Case Report

Atypical Intra-diploic Epidermoid Cyst: 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 Atypical Intra-diploic Epidermoid Cyst: A Case Report Dr. Ruchita Satish Gaonkar, Dr. Prakashini K, Dr. Rajagopal K.V, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6345201/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Intra-diploic epidermoid cysts of the skull are rare, benign lesions, with fewer than 100 reported cases. These cysts typically present as expansile bone lesions but can exhibit atypical imaging featuresthat may complicate diagnosis. Case Presentation We describe a case of a 30-year-old womanwho presented with right-sided tinnitus, earache, and a palpable peri-auricular mass. High-resolution computed tomography and magnetic resonance imaging demonstrated a cystic lesion within the right temporal bone, extending into the cerebellopontine angle, jugular foramen, and external auditory canal. The lesion caused lytic destruction of adjacent bony structuresand exhibited peripheral contrast enhancement without restricted diffusion, which is atypical for epidermoid cysts. Histopathological examination confirmed an intra-diploic epidermoid cyst. Conclusion This case highlights the radiological variability of intra-diploic epidermoid cysts, particularly the potential for enhancement and absence of diffusion restriction, which can mimic more aggressive pathologies. Radiologists should consider epidermoid cysts in the differential diagnosis of cerebellopontine angle masses, especially when encountering lesions with bone destruction and atypical enhancement patterns. Intra-diploic Epidermoid cyst Skull base Cerebellopontine angle CT MRI Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 BACKGROUND Intracranial epidermoid cysts constitute less than 1% of all intracranial tumours and are benign, arising from ectodermal cell rests within the skull, composed of keratin and cholesterol ( 1 , 2 ). Intra-diploic epidermoid cysts, an uncommon subtype, are predominantly intradural and can either be congenital or acquired following trauma or surgery. The occurrence of intra-diploic epidermoid cysts is rare; however, they appear similar to epidermoid cysts elsewhere in the body. On CT, they appear as lobulated areas of bone erosions with sclerotic margins and calcifications within ( 4 ). They are usually encountered as cystic lesions following cerebrospinal fluid signal intensity on MRI on all sequences except FLAIR, show diffusion restriction and do not enhance, due to lack of vascularity within ( 4 , 5 ). Treatment usually is complete surgical excision and prognosis is good ( 1 , 2 ). CASE PRESENTATION A 30-year-old woman presented with a six-month history of right-sided tinnitus, followed by progressive earache and hearing loss over the past month. She also reported a history of bloody ear discharge six months earlier. There was no history of fever, purulent ear discharge, facial asymmetry, dysphagia, loss of taste, dizziness, gait imbalance, trauma, or prior surgery. The patient had no known comorbidities. Clinical Examination On physical examination, a 22×20 mm peri-auricular mass with a smooth surface and well-defined margins was observed (Fig. 1 a and b). The mass was non-mobile in any direction, with no local tenderness or rise in temperature. Investigations Pure tone audiometry revealed moderate to severe sensorineural hearing loss in the right ear. Subsequently, an MRI of the brain was performed, Fig. 2 , focusing on the right inner ear, followed by a high-resolution CT (HRCT), Fig. 3 , of the temporal bones. Based on imaging findings, the differential diagnosis included vestibular schwannoma with cystic changes, atypical epidermoid cyst, infected arachnoid cyst, and jugulotympanic paraganglioma. To rule out paraganglioma, a digital subtraction cerebral angiography (DSA) was performed (Fig. 4 ). It revealed normal flow in the right internal carotid artery (ICA), external carotid artery (ECA), and common carotid artery (CCA), with no aneurysm, AVM, AVF, or abnormal tumoral blush, effectively excluding a vascular etiology. TREATMENT The patient underwent surgical excision using a combined transmastoid and retrosigmoid approach. The lesion was opened, and intralesional decompression was performed. The cyst appeared yellowish-white, with a soft-to-firm consistency. The mastoid cavity was then packed with autologous fat harvested from the thigh. Histopathological examination of the excised tissue revealed a grey-white gelatinous tissue. Microscopic analysis showed a cyst lined by stratified squamous epithelium, with keratin flakes, vascular channels, and focal cartilage nodules at the periphery (Fig. 5 ). These findings confirmed the diagnosis of an intra-diploic epidermoid cyst. OUTCOME AND FOLLOW-UP OUTCOME AND FOLLOW-UP Postoperatively, the patient developed difficulty swallowing and tolerating oral feeds. Further evaluation confirmed twelfth cranial nerve paresis, which was managed conservatively. A follow-up CT scan (Fig. 6 ) showed no evidence of residual tumor, haemorrhage, or hydrocephalus. Postoperative changes included air foci and fat attenuation due to the harvested graft. The patient was discharged on postoperative day three with stable vitals. Over time, she demonstrated clinical improvement, with complete resolution of tinnitus and headache. DISCUSSION Epidermoid cysts are slow growing encapsulated benign inclusion cysts arising from ectodermal cell rests and are lined by squamous epithelium ( 1 , 2 ).Intracranial epidermoid cysts can either be extra-dural or intra-dural. The most common intra-dural locations are the cerebellopontine angle ( 13 ), followed by suprasellar cistern and fourth ventricle. Extradural epidermoid cysts are intra-diploic involving parietal and occipital bones, less commonly the greater wing of sphenoid, and petrous apex ( 6 , 7 , 8 ). Intra-cranial diploic epidermoid cysts usually begin as painless lump under the scalp ( 8 ). The presenting symptoms of diploic epidermoid cysts are due to their location, most common being headaches, cranial nerve deficits (tinnitus, vertigo, etc), cerebellar symptoms, seizures, recurrent aseptic meningitis ( 7 , 8 ). In our case the patient presented with painless lump, headache and tinnitus. The epidermoid cysts grow with finger-like extensions along the clefts and spaces to encircle the blood vessels, cranial nerves; cerebellar hemispheres and brainstem ( 10 ). These can remain undetected or cause symptoms by irritation of surrounding tissues, such as cranial nerve palsy. Repeated rupture of capsule and spillage of cystic material into CSF can result in aseptic meningitis, arachnoiditis and encephalitis ( 10 , 11 ). Radiological features are large lytic areas with erosion and expansion of both inner and the outer tables of the skull with sharply defined sclerotic borders and calcification ( 8 ). On CT, the epidermoid cysts usually appear as non-enhancing hypodense lesions with calcifications within, sclerotic margins and associated bony defects ( 3 , 8 ). Rarely, they can appear hyperdense due to haemorrhage or proteinaceous components – known as white epidermoid cyst ( 12 ). While on MRI, they are iso to hypointense on T1W, hyperintense on T2W, heterogeneous on FLAIR depending on its protein content with diffusion restriction which is characteristic and they do not show enhancement on post contrast sequences ( 3 , 4 , 8 , 9 , 17 ).In our case, the lesion showed T1 hypointensity, T2 hyperintensity, FLAIR heterogeneity but other radiological features like lack of diffusion restriction and peripheral post contrast wall enhancement were dissimilar to existing literature. These atypical imaging features can be attributed due to their protein content; the timing of ectodermal tissue sequestration during foetal development may account for the occurrence of atypical epidermoid cysts ( 3 , 19 ). CT also revealed erosion of walls of EAC, tegmen antri of mastoid, and jugular walls. Although radiological features may be suggestive, definitive diagnosis is made by surgical excision and histopathological evaluation. Before histopathological confirmation, our clinico-radiological differential diagnosis based on cranial MRI and CT and involvement of CP angle were vestibular schwannoma with cystic changes, atypical epidermoid cyst, infected arachnoid cyst and jugulotympanic paraganglioma. Unlike our case, paragangliomas usually show salt and pepper appearance with intense post contrast enhancement and tumour blush on digital subtraction angiography ( 15 ). After histopathological confirmation, looking retrospectively, vestibular schwannoma generally are avidly enhancing lesions which when undergo cystic changes often have an intensely enhancing solid component ( 18 ), but in our case there was evidence of only peripheral enhancement and no obvious soft tissue component. Arachnoid cysts follow CSF signal intensity characteristics on all sequences including FLAIR and show no diffusion restriction, they usually cause thinning and remodelling of adjacent bones rather than bone destruction ( 14 ). Although in our case the lesion did not show diffusion restriction, features of FLAIR heterogeneity and adjacent bony destruction were in favour of epidermoid cyst. Treatment of symptomatic intracranial epidermoid cysts is surgical excision as they tend to grow and erode the skull ( 1 , 2 , 6 , 8 ). In addition, they can become complicated due to rupture or infection of the lesion ( 10 , 11 ). Surgical approach is based on the location and extent of the lesion ( 16 ), as in our case due to involvement of temporal bone and right cerebellopontine angle, trans-mastoid and retro-mastoid combined approach was used. Recurrence rate is common, especially after subtotal excision where the cyst wall or the lesion itself is not completely excised ( 16 ). As they also tend to recur, depending on the type of excision (recurrence rate 7 times more with subtotal resection) and if any cyst wall is left behind, follow up with serial MRI is mandatory ( 16 ). CONCLUSION This case underscores the importance of recognizing atypical imaging features in epidermoid cysts, which can lead to diagnostic uncertainty. While the classic presentation includes diffusion restriction and lack of enhancement, variations in imaging patterns should not exclude epidermoid cysts from the differential diagnosis. Additionally, given their potential for local invasion and recurrence, a multidisciplinary approach involving radiologists, neurosurgeons, and pathologists is critical for optimal management. Abbreviations AVF Arteriovenous fistula AVM Arteriovenous malformation CCA Common carotid artery CP Cerebellopontine CSF Cerebrospinal fluid CT Computed tomography DSA Digital subtraction angiography ECA External carotid artery FIESTA Fast imaging employing steady-state acquisition FLAIR Fluid attenuated inversion recovery HRCT High resolution computed tomography HPE Histopathological examination ICA Internal carotid artery MRI magnetic resonance imaging SWI Susceptibility weighted imaging Declarations Ethics approval, consent to participate and publish Institutional Ethics committee approval was obtained. Informed written consent was obtained from the patient for publication of this case report and any accompanying images. Availability of data and materials All data is available on reasonable request to the authors. Competing interests The authors declare that they have no competing interests Funding No funding received to conduct this study. Acknowledgements We would like to acknowledge Dr. Megha Murali, Assistant Professor and Dr Geetha V. Additional Professor from Department of Pathology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, for performing and reviewing the histopathological examination of the specimen. Authors' contributions RSG analyzed and interpreted the patient data as well as contributed in drafting the manuscript. PK and RKV helped in interpreting the MRI scan, analysing the data, and guiding in manuscript preparation. AD made the necessary modifications and was also a major contributor in finalising the manuscript. All authors read and approved the final manuscript. References Spinato G, Gaudioso P, Falcioni M, Mosto MCD, Cocuzza S, Maniaci A, et al. Giant Epidermoid Cyst of Posterior Fossa—Our Experience and Literature Review. Dose-Response. 2021;19(1):155932582110020. Luis Rafael Moscote-Salazar, Satyarthee GD, Calderon-Miranda WG, Agrawal A, Hernando Raphael Alvis-Miranda, Alcala-Cerra G et al. Intradiploic pterional epidermoid tumor: A case report and review of literature. Journal of pediatric neurosciences. 2017;12(3):262–2. Kallmes DF, Provenzale JM, Cloft HJ, McClendon RE. Typical and atypical MR imaging features of intracranial epidermoid tumors. Am J Roentgenol. 1997;169(3):883–7. Vion-Dury J, Vincentelli F, Jiddane M, Van Bunnen Y, Rumeau C, Grisoli F, et al. MR imaging of epidermoid cysts. Neuroradiology. 1987;29(4):333–8. Liu P, Yukihisa Saida, Yoshioka H, Yuji Itai. MR Imaging Epidermoids Cerebellopontine Angle. 2003;2(3):109–15. Krupp W, Heckert A, Holland H, Meixensberger J, Fritzsch D. Giant intradiploic epidermoid cyst with large osteolytic lesions of the skull: a case report. J Med Case Rep. 2012;6(1). Inoue Y, Ohata K, Nakayama K, Haba T, Miyuki S. An unusual middle fossa interdural epidermoid tumor. J Neurosurg. 2001;95(5):902–4. Kerem Bikmaz M, Cosar, Bek S, Gokduman CA, Arslan M, Celal A, Iplikcioglu. Intradiploic epidermoid cysts of the skull: a report of four cases. Clin Neurol Neurosurg. 2005;107(3):262–7. Arana E, Fernandez Latorre F, Revert Ángeles, Menor F, Riesgo P, Liaño F, et al. Intradiploic epidermoid cysts. 1996;38(4):306–11. Nager Gt. Epidermoids involving the temporal bone: clinical, radiological and pathological aspects. PubMed. 1975;85(12 Pt 2 Suppl 2):1–21. ‌White AK, Jenkins HA, Coker NJ. Intradiploic Epidermoid Cyst of the Sphenoid Wing. Archives otolaryngology–head neck Surg. 1987;113(9):995–9. Jamjoom DZ, Alamer A, Tampieri D. Correlation of radiological features of white epidermoid cysts with histopathological findings. Sci Rep. 2022;12(1). Bonneville F, Sarrazin JL, Marsot-Dupuch K, Iffenecker C, Yves-Sébastien Cordoliani, Doyon D, et al. Unusual Lesions Cerebellopontine Angle: Segmental Approach. 2001;21(2):419–38. Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. Williams MD. Paragangliomas of the Head and Neck: An Overview from Diagnosis to Genetics. Head Neck Pathol. 2017;11(3):278–87. Shear BM, Jin L, Zhang Y, David WB, Fomchenko EI, Erson-Omay EZ et al. Extent of resection of epidermoid tumors and risk of recurrence: case report and meta-analysis. J Neurosurg [Internet]. 2019;1–11. Santhosh K, Thomas B, Radhakrishnan VV, Saini J, Kesavadas C, Gupta AK, et al. Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts. J Magn Reson Imaging. 2009;29(4):967–70. Tali ET, Yuh WT, Nguyen HD, Feng G, Koci TM, Jinkins JR et al. Cystic acoustic schwannomas: MR characteristics. American Journal of Neuroradiology [Internet]. 1993 Sep 1 [cited 2024 May 11];14(5):1241–7. Law EKC, Lee RKL, Ng AWH, Siu DYW, Ng HK. Atypical Intracranial Epidermoid Cysts: Rare Anomalies with Unique Radiological Features. Case Rep Radiol. 2015;2015:1–4. 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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-6345201","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":453267840,"identity":"52d86852-d54d-46ff-afc9-4378e0a34348","order_by":0,"name":"Dr. Ruchita Satish Gaonkar","email":"","orcid":"","institution":"Kasturba Medical College, Manipal; Manipal Academy of Higher Education (MAHE), Manipal, Karnataka 576104","correspondingAuthor":false,"prefix":"Dr.","firstName":"Ruchita","middleName":"Satish","lastName":"Gaonkar","suffix":""},{"id":453267842,"identity":"3003eaa9-f5eb-411e-8e93-d3a9eb0b8c2c","order_by":1,"name":"Dr. Prakashini K","email":"","orcid":"","institution":"Kasturba Medical College, Manipal; Manipal Academy of Higher Education (MAHE), Manipal, Karnataka 576104","correspondingAuthor":false,"prefix":"Dr.","firstName":"Prakashini","middleName":"","lastName":"K","suffix":""},{"id":453267843,"identity":"b0545e83-9c1d-4b8b-aaa1-475247912988","order_by":2,"name":"Dr. Rajagopal K.V","email":"","orcid":"","institution":"Kasturba Medical College, Manipal; Manipal Academy of Higher Education (MAHE), Manipal, Karnataka 576104","correspondingAuthor":false,"prefix":"Dr.","firstName":"Rajagopal","middleName":"","lastName":"K.V","suffix":""},{"id":453267845,"identity":"5f3b86a3-0a07-43b5-aae4-0af75f932595","order_by":3,"name":"Dr. Arushi Dhall","email":"data:image/png;base64,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","orcid":"","institution":"Kasturba Medical College, Manipal; Manipal Academy of Higher Education (MAHE), Manipal, Karnataka 576104","correspondingAuthor":true,"prefix":"Dr.","firstName":"Arushi","middleName":"","lastName":"Dhall","suffix":""}],"badges":[],"createdAt":"2025-03-31 13:23:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6345201/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6345201/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82355151,"identity":"5aead8f9-20eb-4688-ac6e-ad92277425a6","added_by":"auto","created_at":"2025-05-09 11:13:13","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":19016,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea) and b). Well-defined right peri-auricular mass with smooth surface and regular margins\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/81b7198dec5dd8177848ed9d.jpg"},{"id":82359251,"identity":"9c1f4803-3e0a-46a8-a455-1b347db9a777","added_by":"auto","created_at":"2025-05-09 11:29:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":437970,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMRI revealed a well-defined lobulated extra-axial FLAIR (a \u0026amp; b) heterogeneous lesion, T1 hypointense (i), T2 hyperintense cystic lesion (c \u0026amp; d), showing peripheral post contrast enhancement (j \u0026amp; k), better seen on heavily T2 weighted sequence FIESTA (e \u0026amp; f) seen in the right jugular foramen and cerebellopontine angle with no evidence of diffusion restriction (g \u0026amp; h) or blooming on SWI (l). Posteriorly, the mass is abutting the right cerebellar hemisphere causing scalloping of the anterior portion of right cerebellar hemisphere (a, b, c, d). Lesion is abutting cisternal part of 7th and 8th nerve complex near its origin, however no extension of lesion into the internal auditory canal (e \u0026amp; f). Anterolaterally, the lesion is seen extending into external auditory canal. Jugular vein and sigmoid sinus compressed by the lesion (j \u0026amp; k), however no evidence of thrombosis. Fluid signal intensity seen within the middle ear with no enhancement and also in mastoid air cells (e \u0026amp; f)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/8f2d723b3c3936bd558ddb15.png"},{"id":82355154,"identity":"0d22a575-c229-4de2-b12e-f995a6e37c8a","added_by":"auto","created_at":"2025-05-09 11:13:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":218560,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea)Axial b)\u0026amp;c) coronal images of HRCT temporal bone showing widening of right jugular fossa with erosion of jugular walls, with erosions of posterior wall of carotid canal, anterior wall of external auditory canal, tegmen antri of mastoid air cells and tympanic part of right temporal bone. d) Axial e) \u0026amp;f) coronal images in soft tissue window show soft tissue density in the right epitympanum, mesotympanum, hypotympanum involving the sinus tympani and facial recess extending to mastoid aditus with extension into mastoid antrum, mastoid air cells with loss of pneumatisation of mastoid air cells and extension to occupy the right cerebellopontine angle.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/7bc2197efb847a177f37bf3e.png"},{"id":82359250,"identity":"70d5f72b-1543-450f-a6dd-4fbe95e50577","added_by":"auto","created_at":"2025-05-09 11:29:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":68328,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDSA showed normal flow in right ICA (a), ECA (b) and CCA (c) with no evidence of aneurysm, AVM or AVF. There were no features of abnormal tumoral blush, thus ruling out paraganglioma.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/b27934fc77e7010011116e06.png"},{"id":82355162,"identity":"4d078388-3001-419e-867d-fb74f3807358","added_by":"auto","created_at":"2025-05-09 11:13:13","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":135572,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHPE showing cyst lined by stratified squamous epithelium overlying loose fibrocollagenous stroma with ectatic blood vessels.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/9229a74d77b2a286642e41a8.jpg"},{"id":82360090,"identity":"98e0f4cb-fb10-4e3f-9d6d-0b424c42806d","added_by":"auto","created_at":"2025-05-09 11:37:13","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":341252,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePost-operative CT brain a), b) and c), d) in bone window; showed post-operative changes in the form of air foci and fat attenuation (due to harvested graft) with no residual lesion.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/8c57ec359a623f4379e16bb4.png"},{"id":109612464,"identity":"e36a095a-36f7-4ee1-93e4-c9ef800e3589","added_by":"auto","created_at":"2026-05-20 07:56:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1561903,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6345201/v1/acd9cf09-92b8-4ff3-b38b-8f5d51ecc82c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eAtypical Intra-diploic Epidermoid Cyst: A Case Report\u003c/p\u003e","fulltext":[{"header":"BACKGROUND","content":"\u003cp\u003eIntracranial epidermoid cysts constitute less than 1% of all intracranial tumours and are benign, arising from ectodermal cell rests within the skull, composed of keratin and cholesterol (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Intra-diploic epidermoid cysts, an uncommon subtype, are predominantly intradural and can either be congenital or acquired following trauma or surgery. The occurrence of intra-diploic epidermoid cysts is rare; however, they appear similar to epidermoid cysts elsewhere in the body. On CT, they appear as lobulated areas of bone erosions with sclerotic margins and calcifications within (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). They are usually encountered as cystic lesions following cerebrospinal fluid signal intensity on MRI on all sequences except FLAIR, show diffusion restriction and do not enhance, due to lack of vascularity within (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Treatment usually is complete surgical excision and prognosis is good (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e"},{"header":"CASE PRESENTATION","content":"\u003cp\u003eA 30-year-old woman presented with a six-month history of right-sided tinnitus, followed by progressive earache and hearing loss over the past month. She also reported a history of bloody ear discharge six months earlier. There was no history of fever, purulent ear discharge, facial asymmetry, dysphagia, loss of taste, dizziness, gait imbalance, trauma, or prior surgery. The patient had no known comorbidities.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eClinical Examination\u003c/h2\u003e \u003cp\u003eOn physical examination, a 22\u0026times;20 mm peri-auricular mass with a smooth surface and well-defined margins was observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and b). The mass was non-mobile in any direction, with no local tenderness or rise in temperature.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eInvestigations\u003c/h3\u003e\n\u003cp\u003ePure tone audiometry revealed moderate to severe sensorineural hearing loss in the right ear. Subsequently, an MRI of the brain was performed, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, focusing on the right inner ear, followed by a high-resolution CT (HRCT), Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, of the temporal bones.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBased on imaging findings, the differential diagnosis included vestibular schwannoma with cystic changes, atypical epidermoid cyst, infected arachnoid cyst, and jugulotympanic paraganglioma.\u003c/p\u003e \u003cp\u003eTo rule out paraganglioma, a digital subtraction cerebral angiography (DSA) was performed (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). It revealed normal flow in the right internal carotid artery (ICA), external carotid artery (ECA), and common carotid artery (CCA), with no aneurysm, AVM, AVF, or abnormal tumoral blush, effectively excluding a vascular etiology.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eTREATMENT\u003c/h3\u003e\n\u003cp\u003eThe patient underwent surgical excision using a combined transmastoid and retrosigmoid approach. The lesion was opened, and intralesional decompression was performed. The cyst appeared yellowish-white, with a soft-to-firm consistency. The mastoid cavity was then packed with autologous fat harvested from the thigh.\u003c/p\u003e \u003cp\u003eHistopathological examination of the excised tissue revealed a grey-white gelatinous tissue. Microscopic analysis showed a cyst lined by stratified squamous epithelium, with keratin flakes, vascular channels, and focal cartilage nodules at the periphery (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). These findings confirmed the diagnosis of an intra-diploic epidermoid cyst.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eOUTCOME AND FOLLOW-UP\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003eOUTCOME AND FOLLOW-UP\u003c/div\u003e \u003cp\u003ePostoperatively, the patient developed difficulty swallowing and tolerating oral feeds. Further evaluation confirmed twelfth cranial nerve paresis, which was managed conservatively.\u003c/p\u003e \u003cp\u003eA follow-up CT scan (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) showed no evidence of residual tumor, haemorrhage, or hydrocephalus. Postoperative changes included air foci and fat attenuation due to the harvested graft.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe patient was discharged on postoperative day three with stable vitals. Over time, she demonstrated clinical improvement, with complete resolution of tinnitus and headache.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eEpidermoid cysts are slow growing encapsulated benign inclusion cysts arising from ectodermal cell rests and are lined by squamous epithelium (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).Intracranial epidermoid cysts can either be extra-dural or intra-dural. The most common intra-dural locations are the cerebellopontine angle (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e), followed by suprasellar cistern and fourth ventricle. Extradural epidermoid cysts are intra-diploic involving parietal and occipital bones, less commonly the greater wing of sphenoid, and petrous apex (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIntra-cranial diploic epidermoid cysts usually begin as painless lump under the scalp (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). The presenting symptoms of diploic epidermoid cysts are due to their location, most common being headaches, cranial nerve deficits (tinnitus, vertigo, etc), cerebellar symptoms, seizures, recurrent aseptic meningitis (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). In our case the patient presented with painless lump, headache and tinnitus.\u003c/p\u003e \u003cp\u003eThe epidermoid cysts grow with finger-like extensions along the clefts and spaces to encircle the blood vessels, cranial nerves; cerebellar hemispheres and brainstem (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). These can remain undetected or cause symptoms by irritation of surrounding tissues, such as cranial nerve palsy. Repeated rupture of capsule and spillage of cystic material into CSF can result in aseptic meningitis, arachnoiditis and encephalitis (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRadiological features are large lytic areas with erosion and expansion of both inner and the outer tables of the skull with sharply defined sclerotic borders and calcification (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). On CT, the epidermoid cysts usually appear as non-enhancing hypodense lesions with calcifications within, sclerotic margins and associated bony defects (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Rarely, they can appear hyperdense due to haemorrhage or proteinaceous components \u0026ndash; known as white epidermoid cyst (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). While on MRI, they are iso to hypointense on T1W, hyperintense on T2W, heterogeneous on FLAIR depending on its protein content with diffusion restriction which is characteristic and they do not show enhancement on post contrast sequences (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).In our case, the lesion showed T1 hypointensity, T2 hyperintensity, FLAIR heterogeneity but other radiological features like lack of diffusion restriction and peripheral post contrast wall enhancement were dissimilar to existing literature. These atypical imaging features can be attributed due to their protein content; the timing of ectodermal tissue sequestration during foetal development may account for the occurrence of atypical epidermoid cysts (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). CT also revealed erosion of walls of EAC, tegmen antri of mastoid, and jugular walls.\u003c/p\u003e \u003cp\u003eAlthough radiological features may be suggestive, definitive diagnosis is made by surgical excision and histopathological evaluation. Before histopathological confirmation, our clinico-radiological differential diagnosis based on cranial MRI and CT and involvement of CP angle were vestibular schwannoma with cystic changes, atypical epidermoid cyst, infected arachnoid cyst and jugulotympanic paraganglioma.\u003c/p\u003e \u003cp\u003eUnlike our case, paragangliomas usually show salt and pepper appearance with intense post contrast enhancement and tumour blush on digital subtraction angiography (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAfter histopathological confirmation, looking retrospectively, vestibular schwannoma generally are avidly enhancing lesions which when undergo cystic changes often have an intensely enhancing solid component (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), but in our case there was evidence of only peripheral enhancement and no obvious soft tissue component.\u003c/p\u003e \u003cp\u003eArachnoid cysts follow CSF signal intensity characteristics on all sequences including FLAIR and show no diffusion restriction, they usually cause thinning and remodelling of adjacent bones rather than bone destruction (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Although in our case the lesion did not show diffusion restriction, features of FLAIR heterogeneity and adjacent bony destruction were in favour of epidermoid cyst.\u003c/p\u003e \u003cp\u003eTreatment of symptomatic intracranial epidermoid cysts is surgical excision as they tend to grow and erode the skull (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). In addition, they can become complicated due to rupture or infection of the lesion (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Surgical approach is based on the location and extent of the lesion (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e), as in our case due to involvement of temporal bone and right cerebellopontine angle, trans-mastoid and retro-mastoid combined approach was used.\u003c/p\u003e \u003cp\u003eRecurrence rate is common, especially after subtotal excision where the cyst wall or the lesion itself is not completely excised (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). As they also tend to recur, depending on the type of excision (recurrence rate 7 times more with subtotal resection) and if any cyst wall is left behind, follow up with serial MRI is mandatory (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThis case underscores the importance of recognizing atypical imaging features in epidermoid cysts, which can lead to diagnostic uncertainty. While the classic presentation includes diffusion restriction and lack of enhancement, variations in imaging patterns should not exclude epidermoid cysts from the differential diagnosis. Additionally, given their potential for local invasion and recurrence, a multidisciplinary approach involving radiologists, neurosurgeons, and pathologists is critical for optimal management.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAVF\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eArteriovenous fistula\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAVM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eArteriovenous malformation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCCA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCommon carotid artery\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCP\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCerebellopontine\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\"\u003eCT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eComputed tomography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eDSA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDigital subtraction angiography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eECA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eExternal carotid artery\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eFIESTA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eFast imaging employing steady-state acquisition\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eFLAIR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eFluid attenuated inversion recovery\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHRCT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHigh resolution computed tomography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHPE\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHistopathological examination\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eICA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInternal carotid artery\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\"\u003eSWI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSusceptibility weighted imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval, consent to participate and publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInstitutional Ethics committee approval was obtained. Informed written consent was obtained from the patient for publication of this case report and any accompanying images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data is available on reasonable request to the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding received to conduct this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to acknowledge Dr. Megha Murali, Assistant Professor and Dr Geetha V. Additional Professor from Department of Pathology, Kasturba Medical College, Manipal Academy of Higher Education (MAHE), Manipal, for performing and reviewing the histopathological examination of the specimen.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRSG analyzed and interpreted the patient data as well as contributed in drafting the manuscript. PK and RKV helped in interpreting the MRI scan, analysing the data, and guiding in manuscript preparation. AD made the necessary modifications and was also a major contributor in finalising the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSpinato G, Gaudioso P, Falcioni M, Mosto MCD, Cocuzza S, Maniaci A, et al. Giant Epidermoid Cyst of Posterior Fossa\u0026mdash;Our Experience and Literature Review. Dose-Response. 2021;19(1):155932582110020.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuis Rafael Moscote-Salazar, Satyarthee GD, Calderon-Miranda WG, Agrawal A, Hernando Raphael Alvis-Miranda, Alcala-Cerra G et al. Intradiploic pterional epidermoid tumor: A case report and review of literature. Journal of pediatric neurosciences. 2017;12(3):262\u0026ndash;2.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKallmes DF, Provenzale JM, Cloft HJ, McClendon RE. Typical and atypical MR imaging features of intracranial epidermoid tumors. Am J Roentgenol. 1997;169(3):883\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVion-Dury J, Vincentelli F, Jiddane M, Van Bunnen Y, Rumeau C, Grisoli F, et al. MR imaging of epidermoid cysts. Neuroradiology. 1987;29(4):333\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu P, Yukihisa Saida, Yoshioka H, Yuji Itai. MR Imaging Epidermoids Cerebellopontine Angle. 2003;2(3):109\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKrupp W, Heckert A, Holland H, Meixensberger J, Fritzsch D. Giant intradiploic epidermoid cyst with large osteolytic lesions of the skull: a case report. J Med Case Rep. 2012;6(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eInoue Y, Ohata K, Nakayama K, Haba T, Miyuki S. An unusual middle fossa interdural epidermoid tumor. J Neurosurg. 2001;95(5):902\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKerem Bikmaz M, Cosar, Bek S, Gokduman CA, Arslan M, Celal A, Iplikcioglu. Intradiploic epidermoid cysts of the skull: a report of four cases. Clin Neurol Neurosurg. 2005;107(3):262\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArana E, Fernandez Latorre F, Revert \u0026Aacute;ngeles, Menor F, Riesgo P, Lia\u0026ntilde;o F, et al. Intradiploic epidermoid cysts. 1996;38(4):306\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNager Gt. Epidermoids involving the temporal bone: clinical, radiological and pathological aspects. PubMed. 1975;85(12 Pt 2 Suppl 2):1\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e\u0026zwnj;White AK, Jenkins HA, Coker NJ. Intradiploic Epidermoid Cyst of the Sphenoid Wing. Archives otolaryngology\u0026ndash;head neck Surg. 1987;113(9):995\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJamjoom DZ, Alamer A, Tampieri D. Correlation of radiological features of white epidermoid cysts with histopathological findings. Sci Rep. 2022;12(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBonneville F, Sarrazin JL, Marsot-Dupuch K, Iffenecker C, Yves-S\u0026eacute;bastien Cordoliani, Doyon D, et al. Unusual Lesions Cerebellopontine Angle: Segmental Approach. 2001;21(2):419\u0026ndash;38.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOsborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliams MD. Paragangliomas of the Head and Neck: An Overview from Diagnosis to Genetics. Head Neck Pathol. 2017;11(3):278\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShear BM, Jin L, Zhang Y, David WB, Fomchenko EI, Erson-Omay EZ et al. Extent of resection of epidermoid tumors and risk of recurrence: case report and meta-analysis. J Neurosurg [Internet]. 2019;1\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSanthosh K, Thomas B, Radhakrishnan VV, Saini J, Kesavadas C, Gupta AK, et al. Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts. J Magn Reson Imaging. 2009;29(4):967\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTali ET, Yuh WT, Nguyen HD, Feng G, Koci TM, Jinkins JR et al. Cystic acoustic schwannomas: MR characteristics. American Journal of Neuroradiology [Internet]. 1993 Sep 1 [cited 2024 May 11];14(5):1241\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLaw EKC, Lee RKL, Ng AWH, Siu DYW, Ng HK. Atypical Intracranial Epidermoid Cysts: Rare Anomalies with Unique Radiological Features. Case Rep Radiol. 2015;2015:1\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Intra-diploic, Epidermoid cyst, Skull base, Cerebellopontine angle, CT, MRI","lastPublishedDoi":"10.21203/rs.3.rs-6345201/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6345201/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIntra-diploic epidermoid cysts of the skull are rare, benign lesions, with fewer than 100 reported cases. These cysts typically present as expansile bone lesions but can exhibit atypical imaging featuresthat may complicate diagnosis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCase Presentation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe describe a case of a 30-year-old womanwho presented with right-sided tinnitus, earache, and a palpable peri-auricular mass. High-resolution computed tomography and magnetic resonance imaging demonstrated a cystic lesion within the right temporal bone, extending into the cerebellopontine angle, jugular foramen, and external auditory canal. The lesion caused lytic destruction of adjacent bony structuresand exhibited peripheral contrast enhancement without restricted diffusion, which is atypical for epidermoid cysts. Histopathological examination confirmed an intra-diploic epidermoid cyst.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis case highlights the radiological variability of intra-diploic epidermoid cysts, particularly the potential for enhancement and absence of diffusion restriction, which can mimic more aggressive pathologies. Radiologists should consider epidermoid cysts in the differential diagnosis of cerebellopontine angle masses, especially when encountering lesions with bone destruction and atypical enhancement patterns.\u003c/p\u003e","manuscriptTitle":"Atypical Intra-diploic Epidermoid Cyst: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-09 11:13:08","doi":"10.21203/rs.3.rs-6345201/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":"8ff8c87c-1810-4fe4-907d-63d9c8e93176","owner":[],"postedDate":"May 9th, 2025","published":true,"recentEditorialEvents":[{"type":"decision","content":"Withdrawn","date":"2026-05-20T07:49:29+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-20T07:56:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-09 11:13:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6345201","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6345201","identity":"rs-6345201","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}