Congenital cerebrospinal fluid fistula through the inner ear and meningitis.

Congenital deformities of the labyrinth of the inner ear can be associated with a fistulous communication between the intracranial subarachnoid space and the middle ear cavity. We describe seven such cases, six confirmed by high resolution CT and one by postmortem histological section. The seven patients all presented with meningitis although a cerebrospinal fluid fistula was demonstrated at subsequent surgery or postmortem. The lesions were bilateral in three patients, unilateral in three and probably bilateral in the postmortem case although only one temporal bone was obtained. In every case there was a dilated sac instead of the normal two and a half turn cochlea on the affected side and this was confirmed at surgery. The demonstration of the basal cochlear turn is of paramount importance in any deaf child presenting with meningitis. A true Mondini deformity with a normal basal turn and some hearing is not at risk of developing a fistula.