Intrinsic Brainstem Epidermoid: Case Report and Literature Review

Abstract

Epidermoid cysts are rare lesions of the central nervous system, representing 1-2% of all intracranial tumours. These mass lesions are typically found in the parasellar region or cerebellopontine angle. As far as we are aware only 15 cases of an intrinsic brainstem epidermoid have been reported in the pediatric population to date. We report a case in which an 8-year-old male patient with an intrinsic brainstem epidermoid was misdiagnosed and treated as a diffuse intrinsic pontine glioma (DIPG). The child was subsequently referred to our unit failing response to treatment at the index hospital. Magnetic resonance imaging (MRI) revealed a well-defined lesion, with clearly distinct borders, that was hypointense on T1WI, hyperintense on T2WI, had minimal contrast enhancement and had restricted diffusion on the DWI/ADC map. With the aid of intra-operative neurophysiological monitoring he underwent surgical resection of the lesion. Histopathology revealed abundant nucleated and anucleated squamous cells, in keeping with an epidermoid tumor. Clinical follow up at 3 months post-surgery showed significant improvement in the child's pre-surgical neurological function. Follow up MRI at 3 months and a year post surgery revealed that the lesion is stable following near total resection. The objective of this case report is to highlight this unusual condition which may otherwise be misdiagnosed and to encourage a more universal acceptance of the need for either brainstem biopsies in atypical brainstem lesions or formal resection of lesions amenable to safe surgical resection.