Abstract
A 37-year-old man with both Mondini dysplasia and normal hearing is reported. The patient visited our clinic with a complaint of unsteadiness. Pure-tone audiometry showed a normal hearing level in both ears. Polytomography and computed tomography (CT) revealed enlargement of the vestibules and lateral semicircular canals in both ears but a normal shape of the cochlea and other semicircular canals. The caloric test indicated severe canal paresis (CP) in the left ear and moderate CP in the right ear, whereas the active head rotation test demonstrated that head-eye coordination was preserved at frequencies of 0.33 and 0.67 Hz but slightly deteriorated at 1.0 Hz. The patient’s unsteadiness seemed to be attributable to a hypofuncion of the bilateral semicircular canals, which may be due to insidious, repeated cerebrospinal fluid otorrhea caused by judo wrestling. Although Mondini dysplasia with normal hearing has been believed to be rare, phylogenetic consideration suggests that more such patients exist than has been assumed.