Basilar invagination and mid-line skeletal abnormalities due to in utero exposure to phenytoin.

A case of basilar invagination which is thought to have arisen from the patient's intrauterine exposure to phenytoin is presented. The patient was treated surgically by foramen magnum decompression and occipito-cervical fusion, and by transoral resection of the clivus. His symptoms of brain stem compression were alleviated and the role of phenytoin in the production of his craniocervical abnormality is discussed.