Intrinsic brainstem white epidermoid cyst: An unusual case report.

Epidermoid cysts involving the brainstem are extremely rare, with only 18 reported cases in the literature and only five purely intrinsic epidermoid cysts within this group. "White epidermoids", a rare entity, have high protein content and show reversed signal intensity on magnetic resonance images. In contrast to the classical variety, these cysts show high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. Here, we report an interesting case of intrinsic brainstem "white epidermoid cyst" in a 15-year-old girl and discuss its clinical characteristics, radiological features, and surgical treatment. The girl presented with a one-year history of progressive quadriparesis, and features of multiple cranial nerve involvement. Because the cyst was purely intrinsic and had altered signal intensity, the diagnosis was initially unclear until definitive neuroimaging was performed using diffusion-weighted magnetic resonance imaging (DW-MRI) sequences.