AUTHOR=Tarnutzer Alexander A. , Bockisch Christopher J. , Buffone Elena , Weber Konrad P. 

TITLE=Hierarchical Cluster Analysis of Semicircular Canal and Otolith Deficits in Bilateral Vestibulopathy

JOURNAL=Frontiers in Neurology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2018.00244

DOI=10.3389/fneur.2018.00244

ISSN=1664-2295

ABSTRACT=Background: Gait imbalance and oscillopsia are frequent complaints of bilateral vestibular loss (BLV). Video-head-impulse testing (vHIT) of all six semicircular canals (SCCs) has demonstrated varying involvement of the different canals. Sparing of anterior-canal function has been linked to aminoglycoside-related vestibulopathy and Menière's disease. We hypothesized that utricular and saccular impairment (assessed by vestibular-evoked myogenic-potentials; VEMPs) may be disease-specific also, possibly facilitating the differential diagnosis.
Methods: We searched our vHIT-database (n=3271) for patients with bilaterally impaired SCC-function who also received ocular VEMPs (oVEMPs) and cervical VEMPs (cVEMPs) and identified 101 patients. oVEMP/cVEMP-latencies above the 95th-percentile and peak-to-peak amplitudes below the 5th-percentile of normal were considered abnormal. Frequency of impairment of vestibular end organs (horizontal/anterior/posterior SCC, utriculus/sacculus) was analyzed with hierarchical cluster analysis and correlated with the underlying etiology.
Results: Rates of utricular and saccular loss-of-function were similar (87.1% vs. 78.2%, p=0.136, Fisher's exact test). oVEMP-abnormalities were found more frequent in aminoglycoside-related BVL compared to Menière's disease (91.7% vs. 54.6%, p=0.039). Hierarchical cluster analysis indicated distinct patterns of vestibular end-organ impairment, showing that the results for the same end-organs on both sides are more similar than to other end-organs. Relative sparing of anterior-canal function was reflected in late merging with the other end-organs, emphasizing their distinct state. An anatomically corresponding pattern of SCC/otolith hypofunction was present in 60.4% (oVEMPs vs. horizontal SCCs), 34.7% (oVEMPs vs. anterior SCCs) and 48.5% (cVEMPs vs. posterior SCCs) of cases. Average (±1SD) number of damaged sensors was 6.8±2.2 out of 10. Significantly (p<0.001) more sensors were impaired in patients with aminoglycoside-related BVL (8.1±1.2) or inner-ear infections (8.7±1.8) compared to Menière-related BVL (5.5±1.5).
Discussion: Hierarchical cluster analysis may help differentiate characteristic patterns of BVL. With a prevalence of ≈80%, utricular and/or saccular impairment is frequent in BVL. The extent of SCC and otolith impairment was disease-dependent, showing most extensive damage in BVL related to inner-ear infection and aminoglycoside-exposure and more selective impairment in Menière's disease. Specifically, assessing utricular function may help in the distinction between aminoglycoside-related BVL and bilateral Menière's disease.