Congenital inner ear malformations without sensorineural hearing loss

It has been reported that normal hearing is rare in patients with severe inner ear vestibular malformations [Kokai H, Oohashi M, Ishikawa K, Harada K, Hiratsuka H, Ogasawara M et al. Clinical review of inner ear malformation. J Otolaryngol Jpn 2003;106(10):1038-44; Schuknecht HF. Mondini dysplasia. A clinical pathological study. Ann Otol Rhinol Laryngol 1980;89(Suppl. 65):1-23; Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: a classification based on embryogenesis. Laryngoscope 1987;97:2-14; Phelps PD. Congenital lesions of the inner ear, demonstrated by tomography. Arch Otolaryngol 1974;100:11-8]. A 37-year-old woman had combined dysplasia of the posterior and lateral semicircular canals (PSCC, LSCC) with normal cochlear development and normal hearing in both ears. She had complained of dizziness for 8 months. High resolution computed tomography (CT) showed hypogenesis of the bony labyrinth in both ears. Bilateral PSCC and LSCC dysplasia and dilatation of the vestibule were detected. Magnetic resonant imaging (MRI) revealed that the deformity of the PSCC was more severe than the LSCC. Although the caloric test of the left ear elicited no nystagmus and there was reduced response in the right ear, the horizontal vestibulo-occular reflex (VOR) was present. Her dizzy sensation disappeared within 3 months without special treatment. The dizziness attack might have been caused by a temporary breakdown of her peripheral vestibular system.