Subarachnoid space: middle ear pathways and recurrent meningitis.

Congenital bony abnormalities of the inner ear may result in a communication between the middle ear and the subarachnoid space. Patients with this anomaly often present with recurrent meningitis associated with acute otitis media or with middle ear fluid. This article presents three cases of recurrent meningitis with open middle ear--subarachnoid space connections. The first two cases involve a cerebrospinal fluid leak into the middle ear via the oval window, both patients having a Mondini-type of inner ear deformity. The pathway in the third case opened into the middle ear along the horizontal portion of the facial nerve. Computed tomography (CT) scanning with metrizamide and differential density calculations helped to identify the abnormal pathway and to confirm that the leak has been closed postoperatively. Use of the CT scanner in these cases can be helpful in planning the surgical closure and in postoperative follow-up.