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

Abstract

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Semicircular canal function in BVL shows disease-specific dissociations, potentially related to reduced vulnerability or superior recovery of the anterior canals. SIGNIFICANCE: 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.

The Video Head Impulse Test

“…vHIT can quantify the absolute level of canal function after treatment with systemic (13) or intratympanic gentamicin (14) and measure bilateral loss of vestibular function (15–17) (see Quantitative Head Impulse Test in Central Vestibular Disorders and New Clinical Disease Patterns Emerging from 3D Video Head Impulse Testing). Tracking the pattern of covert saccades after UVL shows that there are changes in the timing and pattern of the saccades which may be related to the adequacy of vestibular compensation.…”

“…Based on these investigations, characteristic patterns of SCC hypofunction started to emerge in patients with BVL: anterior SCC function was selectively spared in about 60% of these patients (Figure 15). As it turned out, AC sparing, determined by gain values (>0.7) and cumulative catch-up saccade amplitudes (<0.73°/trial), were associated with aminoglycoside vestibulotoxicity and Menière’s disease (17). Therefore, routine vHIT measures of all six SCCs may help to identify the underlying cause in patients with BVL.…”

Testing of the Semicircular Canal Function in Vertigo and Dizziness

“…Preserved AC function was associated with aminoglycoside toxicity, MD and BVL of unknown origin. No such sparing of specific SCCs was found for inner ear infections, cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS) and sensorineural hearing loss [81]. CANVAS is a late-onset ataxia with a neuropathy and a BV [82].…”

Video Head Impulse Testing: From Bench to Bedside

“…22 Many vestibular disorders, both peripheral [23][24][25] and central, [26][27][28] rapidly evolve over time and have known specific treatments and can now be reassessed without subjecting patients to repeated lengthy testing. As both lateral and vertical SCCs can be evaluated, different patterns of SCC involvement have emerged that carry diagnostic significance: selective sparing of AC function has been demonstrated to be specific for certain causes of bilateral vestibulopathy (BV), 29 whereas selective impairment of PC function is uncommon and usually associated with additional audiovestibular loss. 30 Despite its advantage of vHIT over traditional vestibular function testing, it should be viewed as a powerful tool that can be used to extend the clinical examination and not as a "competitor" that diminishes the role of other vestibular function tests.…”