A case of inner ear malformations that was administered a detailed vestibular test battery

Abstract

　Inner ear malformations are rarely encountered, but are present in approximately 20% of the patients with congenital sensorineural hearing loss. At present, hearing aids and cochlear implantation are considered as effective treatments for hearing loss associated with inner ear malformations. Therefore, classification of inner ear malformations is based on the cochlear anatomy from a therapeutic point of view. On the other hand, few studies have reported on the vestibular functions of patients with inner ear malformations. We administered a detailed vestibular test battery to a patient with inner ear malformations, and found an occult response on the vHIT, delivered under the absence of the corresponding semi-circular canal.

　A 26-year-old female patient presented with a history of hearing loss in her left ear since childhood. MRI revealed only a hypoplastic vestibule, with no evident cochlea or semicircular canals in the left inner ear. Although impulses toward the left lateral and left posterior canals elicited reduced VOR (vestibulo-ocular reflex) gains on vHIT (video head impulse test), as expected, an impulse toward the left anterior canal triggered complete VOR gain. The discrepancies between the anatomical findings and the results of functional examination in this case are discussed.

　Vestibular function of the inner ear malformations is an important topic that needs to be clarified. With diagnostic imaging and vestibular function tests having become more and more advanced in recent years, further accumulation and study of cases of inner ear malformations are warranted in the future.