Labyrinthine anomalies with normal cochlear function.

Three cases of labyrinthine anomaly confirmed by polytomography and CT scan are reported. They showed similar dysplasia of the bony labyrinth: dilation and fusion of the lateral semicircular canal (SCC) and of the vestibule with a normally shaped cochlea and other SCCs. One side was involved in 2 cases and both sides in 1 case. The 1st case showed normal hearing levels with markedly reduced response to caloric stimulation in the affected ear. The 2nd case showed conductive hearing loss due to cholesteatoma with normal bone conduction hearing levels and normal caloric response. The 3rd case showed bilateral conductive hearing loss of unknown cause. The classification of labyrinthine anomalies and labyrinthine functions is discussed. Labyrinthine anomaly detected by CT scan and polytomography can be present in patients with normal cochlear and/or vestibular function.