CSF fistula in a patient with Mondini deformity: demonstration by CT cisternography.

In 1791 , Mondini described a membranous and bony dysplasia of the inner ear in a congenitally deaf child (1]. Classically, the Mondini deformity consists of a cochlea containing a normal basal turn and a total of 1.5 rather than 2.5 turns; the middle and apical turns are incorporated into a single sac. Because dysplasia of the labyrinth may be associated with dural dehiscence and a bony defect in the internal auditory canal [2] and with an abnormal stapes footplate (1], a CSF fistula between the posterior fossa and middle ear can occur. In patients with a congenital inner ear anomaly, a CSF fistula has been identified by fluorescein cisternography at surgery [3], and by conventional tomography [4, 5], radionuclide cisternography [6], or cisternal Pantopaque tomography (2, 6, 7] preoperatively. To our knowledge, this is the first report of a CSF fistula of the inner ear demonstrated by CT cisternography.