|Year : 2015 | Volume
| Issue : 4 | Page : 280-281
A rare presentation of posterior fossa epidermoid: With acute bleed
Sandeep Talari, Satya Varaprasad Kadali, Vijay Kumar Pallikonda
Department of Neurosurgery, Andhra Medical College, King George Hospital, Visakhapatnam, Andhra Pradesh, India
|Date of Web Publication||14-Dec-2015|
Department of Neurosurgery, Andhra Medical College, King George Hospital, Maharanipeta, Visakhapatnam - 530 002, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
A 13-year-old female presented with sudden onset of severe headache and altered sensorium. Computed tomography (CT) scan showed a hyperdense midline mass in the posterior fossa. At preoperative diagnosis, the mass was thought to be a hemangioblastoma or pilocytic astrocytoma with bleed. Operative findings and histological examination revealed spontaneous bleed into epidermoid cyst. This uncommon presentation of intracranial epidermoid cyst has prompted us to report the case.
Keywords: Acute bleed, epidermoid, posterior fossa, rare presentation
|How to cite this article:|
Talari S, Kadali SV, Pallikonda VK. A rare presentation of posterior fossa epidermoid: With acute bleed. J NTR Univ Health Sci 2015;4:280-1
| Introduction|| |
Intracranial epidermoids are commonly found in the third and fourth decades of life. The cerebellopontine angle and parasellar regions are the commonest locations. A rare case of hyperdense epidermoid, which was mistaken for pilocytic astrocytoma/hemangioblastoma with bleed, is reported, and the literature on the various factors resulting in computed tomography (CT) hyperdense epidermoid cyst is reviewed.
| Case report|| |
A 13-year-old female presented with history of headache for 2 months and sudden loss of consciousness followed by altered sensorium. There was no history of trauma. The patient regained sensorium after admission and treatment for 1 day. Central nervous system examination revealed bilateral papilledema and truncal ataxia. Initial CT scan, done before being referred to our hospital, showed a large hyperdense homogenous oval mass in the posterior fossa with no contrast enhancement. The fourth ventricle was compressed anteriorly [Figure 1]a, b and c. Magnetic resonance imaging (MRI) after 3 days of admission revealed the lesion to be hypointense in T1 and hyperintense in T2 with no contrast enhancement. Preoperative diagnosis of spontaneous hemorrhage in a tumor was made. The lesion was explored through a midline suboccipital craniotomy. A large cyst with a yellowish thin-walled capsule containing brownish flaky material was seen. The lesion was removed completely. The postoperative period was uneventful and the patient recovered completely. Histopathological examination showed that the capsule was made up of stratified squamous epithelium and the diagnosis of epidermoid was made. The patient was followed up for 11 months and she is asymptomatic. CT scan after 6 months and 11 months of surgery did not reveal recurrence of the tumor.
|Figure 1: (a) CT brain showing large hyperdense mass in posterior fossa with compression of fourth ventricle, cerebellar vermis, cerebellar hemispheres, and brainstem (b) CT brain showing large hyperdense mass in posterior fossa with compression of the fourth ventricle, cerebellar vermis, cerebellar hemispheres, and brainstem (c) CT brain coronal and sagittal image showing large hyperdense mass in posterior fossa|
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| Discussion|| |
Intracranial epidermoid cysts comprise 0.2-1% of all intracranial neoplasms.  They arise from displaced midline ectodermal cells between the third and fifth weeks of gestation, during closure of the neural tube. These tumors have an affinity for basal subarachnoid cisterns and they enlarge slowly through accumulation of normally dividing cells, with a growth rate resembling the growth of human epidermis. 
Clinical presentation is therefore typically prolonged. Acute presentation, as seen in the present case, is an uncommon presentation of intracranial epidermoid cyst.
CT scan is the single most important investigation for the diagnosis of epidermoid cyst. The characteristic CT scan appearance of an epidermoid cyst includes an irregular, well demarcated, low-density lesion without contrast enhancement. The low density is attributed to the lipid component and cholesterol. Calcification is rare in epidermoids and is usually marginal, probably due to peritumoral leak of its contents with secondary dystrophic calcification. Hyperdense epidermoids are very rare.
Braun et al. proposed that keratinized debris and its saponification to calcium soaps are the cause of the homogeneous hyperdensity of these masses.  The high density is also due to the protein concentration. 
There are only two reports of spontaneous hemorrhage as the cause of hyperdensity of intracranial epidermoid on CT scan.  However, in both those cases, presentation was not acute, as was seen in the present case. Hasegawa et al. suggested that hemorrhage occurs continuously or intermittently from the small fibrous nodules containing numerous vessels, which lead to hemosiderin deposits in the cells, and that was the cause of hyperdensity on CT scan. 
| Conclusion|| |
Such rare presentations of epidermoid cyst should be kept in mind while dealing with hyperdense lesions in plain CT scan
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Conflicts of interest
There are no conflicts of interest.
| References|| |
Hasegawa h, bitoh s, nakata m, fujiwara m, yasuda h. Intracranial epidermoid mimicking meningioma. Surg neurol 1980;15:372-4.
Tekkök ih, cataltepe o, saðlam s. Dense epidermoid cyst of the cerebellopontine angle. Neuroradiology 1991;33:255-7.
Braun if, naidich tp, leeds ne, koslow m, zimmerman hm, chase ne. Dense intracranial epidermoid tumors. Computed tomographic observations. Radiology 1977;122:717-9.
Ito y, kaku m, kodama t, matsukado yintracranial high density epidermoid -classification of ct scan findings and chemical analysis of the cystic content (author′s transl). No shinkei geka 1980;8:645-8.