Disease-specific sparing of the anterior semicircular canals in bilateral vestibulopathy.

Abstract

Bilateral vestibular loss (BVL) is often diagnosed with great delay and an underlying cause is only identified in 50-80%. We measured horizontal and vertical semicircular canal function using the video-head-impulse test (vHIT) and hypothesized that specific vHIT-patterns may be linked to certain etiologies. We retrospectively analyzed 109 BVL-patients linked to aminoglycoside vestibulotoxicity (n=16), Menière's disease (n=10), infectious inner-ear disorders (n=11), sensorineural hearing-loss (n=11), cerebellar-ataxia-neuropathy-vestibular-areflexia-syndrome (CANVAS, n=5), other causes (n=19) as well as those with unknown origin (n=47). Vestibulo-ocular reflex gains and cumulative saccade amplitudes were measured with vHIT, and the functional integrity of all semicircular canals was rated. Overall, anterior canal hypofunction (n=86/218) was identified significantly (p<0.001) less often than horizontal (n=186/218) and posterior (n=194/218) hypofunction. Preserved anterior canal function was associated with aminoglycoside vestibulotoxicity, Menière's disease and BVL of unknown origin, while no such sparing was found for inner-ear infections, CANVAS and sensorineural hearing loss. Semicircular canal function in BVL shows disease-specific dissociations, potentially related to reduced vulnerability or superior recovery of the anterior canals. In patients with suspected BVL we recommend quantifying vHIT gains and saccade amplitudes for all semicircular canals as the pattern of canal hypofunction may help identifying the underlying disorder.