A patient is reported who had progressive neurological changes secondary to congenital malformation and subluxation of the atlanto-axial joint. An occipitocervical fusion was performed as a prophylactic measure. A severe neck injury of the flexion-extension type thirteen months after operation resulted in only minor symptoms. Had this patient's atlanto-axial joint not been stabilized by a solid fusion prior to this accident, transection of the cord might well have been the outcome.