Congenital intramedullary spinal dermoid cyst associated with an Arnold-Chiari malformation

Summary Clinical and neuropathological studies of a case of congenital intramedullary spinal dermoid tumor in a patient with typical Arnold-Chiari malformation have been presented. The bulk of the tumor mass was located at C₇ level and extended downward for about 3 cm. Numerous well formed hairs were grossly noted within the lesion. Microscopic examination revealed the presence of keratin squams, hair and hair follicles in chronic inflammatory granulation tissue. These histological features suggest that the dermoid has ruptured and therefore the cyst walls could not be identified as such but the content induced prominent chronic inflammatory granulomatous reaction. The rarity of the lesion, especially at the cervical and upper thoracic level and its unique association with an Arnold-Chiari malformation are discussed.