Epidermoid tumors are rarely encountered within the fourth ventricle. There are slightly more than 100 cases reported in the literature. Congenital posterior arch defects of the atlas are also rare with less than 50 cases reported in the literature. The coexistence of these two pathologies in one patient has not been previously reported. We present a 51-year- old-woman with an epidermoid tumor of the fourth ventricle and accompanying posterior arch defect of the atlas.

Keywords: Epidermoid tumor, fourth ventricle, atlas, posterior arch, congenital anomaly