[A case of diploic epidermoid invading intradurally, which was diagnosed by MR diffusion-weighted image].

A case of diploic epidermoid in the right parietal bone was presented. A 66-year-old male was admitted to our hospital because of aphasia. Plain skull radiogram showed an osteolytic lesion in the right parietal bone. Computed tomography revealed a mass with destruction of the parietal bone extending from an inner to an outer table. The mass was shown by MR imaging as hypointensity on the T1-weighted image and as hyperintensity on the T2-weighted image. The hyperintensity became more remarkable by using a diffusion technique. Based on these findings, a preoperative diagnosis of right parietal epidermoid was made. The mass was totally removed and diagnosed pathologically as epidermoid. It was concluded that diploic epidermoid invading intradurally could be differentiated from other osteolytic tumors by using MR diffusion-weighted image.