Mondini dysplasia--late complications.

Mondini's deformity is the second most common malformation seen in congenital genetic deafness. It is characterized by bony and membranous abnormalities of the inner ear, with a wide range of morphological and functional abnormalities. The importance of the Mondini malformation is that the patient is at an increased risk of developing meningitis or bilateral total hearing loss (or both) at an early age. Six cases are presented which illustrate the various sequelae of the Mondini malformation including meningitis, vertigo, and auditory deterioration. Decompression of the endolymphatic sac was undertaken in three patients. Emphasis is placed on the danger of head trauma, even minor, in these patients. The necessity of early diagnosis with adequate patient counseling is stressed.