CHILDHOOD SELLAR DERMOID CYST MIMICKING A CRANIOPHARYNGIOMA: THE ADDED BENEFIT OF MRI SCAN

Abstract

Abstract

Background: Intrasellar brain dermoid cysts are extremely unusual cases with or without sudden symptoms. It is a congenital dysembryogenic lesion that is formed during the period of neural tube closure, by the trapping of embryonic ectoderm. This defect explains the propensity of dermoid cyst for the midline localization. The discovery of completely asymptomatic dermoid cysts in the pediatric population is exceedingly rare. Despite the advances in imaging modalities, it sometimes remains difficult to exclude the differential diagnosis of craniopharyngioma.

Case report: We describe a case of a 07-year-old boy addressed for suspicion of craniopharyngioma diagnosed by decreased visual acuity and bitemporal hemianopia. Endocrine workup showed pituitary hormones within normal levels. CT scan was done which shows a large hypodense sellar lesion with intralesional calcifications. Despite the unusual localization and size of this lesion, an MRI brain was performed which showed a large abnormal signal intensity mass in the sella. It shows heterogenous signals on T2 weighted and FLAIR images, hyperintense signals on T1 weighted images without post contrast enhancement. The diagnosis of craniopharyngioma was ruled out in favour of a dermoid cyst.

Conclusion: The reported case reveals an unusual localization of a dermoid cyst, which caused a diagnostic challenge. In the sellar area, it is often not fruitful to differentiate craniopharyngioma and dermoid cyst as they may have very similar CT findings however multisequential MRI imaging thus helps and gives an added benefit in formulating the diagnosis of sellar dermoid by their signal changes in different sequences of MRI.

Keywords: Craniopharyngioma; Dermoid cyst; MRI; Sellar.