Unusual imaging appearance of an intracranial dermoid cyst

Abstract

Intracranial dermoid cysts have characteristic CT and MR imaging findings that generally make preoperative diagnosis straightforward. Enhancement of uncomplicated intradural dermoid cysts on CT or MR studies has been reported but is rare. We present a case of a posterior fossa dermoid cyst that was not only hyperattenuating on CT scans but also contained a mural nodule with clear evidence of enhancement on MR images.

fig 1.

18-year-old girl with occipital headaches of 8 weeks' duration. A, Unenhanced CT scan shows a hyperattenuating posterior fossa lesion with posterior mural nodule. B, Gradient-echo MR image shows marked hypointensity with a frondlike mural nodule. C and D, Pre- (C) and postcontrast (D) T1-weighted MR images show hyperintensity of the cystic contents and clear evidence of contrast enhancement of the mural nodule. E, Sagittal unenhanced T1-weighted MR image shows marked cerebellar tonsillar herniation through the foramen magnum and obliteration of the fourth ventricle. F, Section of cyst wall (lumen indicated by asterisk) shows a lozenge-shaped deposit of calcium with a clear space centrally, numerous cholesterol deposits (large black arrowhead), and a leash of vessels (small black arrowhead) (hematoxylin-eosin, original magnification ×25).