Bilateral Horizontal Canal Dysplasia Presenting as Hearing Loss With Recurrent Vertigo Mimicking Meniere’s Disease

We report an extremely rare case with bilateral horizontal semicircular canal (HSC) dysplasia presenting as hearing loss with recurrent vertigo mimicking Meniere's disease in a previously healthy 49-year-old male patient. HSC malformation is one of the common isolated developmental anomalies of the bony labyrinth usually associated with varying degree of hearing loss. He suffered from recurrent episodes of vertigo lasting more than 20 minutes accompanied by left hearing loss and tinnitus for 3 years. Pure-tone audiometry revealed a mild to moderate hearing loss at low frequencies in the left ear. Bithermal caloric testing revealed significant left-sided canal paralysis, but other vestibular testing was normal. Computerized tomography (CT) of the temporal bone showed the left HSC hypoplasia lacking a central bony island fused together with an enlarged vestibule, and right dysplasia, finally diagnosed with bilateral HSC dysplasia. Meniere's disease-like recurrent vertigo attack and hearing loss were suspected to be caused by subsequent endolymphatic hydrops which could be due to HSC dysplasia.