Diverse clinical and laboratory manifestations of bilateral vestibulopathy.

OBJECTIVES/HYPOTHESIS To identify the clinical and laboratory characteristics of bilateral vestibulopathy (BVP) on the video head impulse test (vHIT). STUDY DESIGN Retrospective chart analysis. METHODS During 23 months, 1,789 patients with dizziness underwent vHIT in our tertiary referral hospital. Of these patients, 65 (3.6%) patients had bilaterally positive catch-up saccades. Based on the caloric test, 15 (group 1) had bilateral caloric weakness, 13 (group 2) had unilateral caloric weakness, and 37 (group 3) had normal caloric responses on both ears. We collected data on these patients regarding demographics, symptoms, gain, and type of saccade on horizontal canal plane vHIT, as well as gain and time constant on velocity step of the rotatory chair test. RESULTS The average age of group 2 (70.38 ± 11.96 years) and group 3 (69.03 ± 11.01 years) were significantly older than that of group 1 (54.80 ± 11.96 years) (P = 0.029, P = 0.003, respectively). Although all patients had bilaterally positive vHIT, 10 of 15 in group 1 were finally diagnosed as classical BVP by clinical features. On comparison of average gain on bilateral horizontal vHIT, groups 2 (0.71 ± 0.17) and 3 (0.80 ± 0.14) had higher gain compared to group 1 (0.45 ± 0.22) (P = 0.001, P = 0.000, respectively). On velocity step test, time constant and gain of group 3 (11.60 ± 3.07, 0.49 ± 0.13) was significantly higher than those of group 1 (4.92 ± 1.36, 0.22 ± 0.17) (P = 0.000, P = 0.004, respectively). On the receiver operating characteristic curve analysis, vHIT alone seemed to be a discordant method for diagnosis of BVP compared to the caloric and step velocity tests. CONCLUSION About 3.6% patients with dizziness showed bilateral vestibular ocular reflex deficit during high-frequency acceleration, which was prevalent especially in elderly patients. Also, positive bilateral vHIT does not always correlate with caloric or rotatory chair test results. This may imply that a diverse spectrum of vestibulopathies exist according to the stimulation frequency of deficit. LEVEL OF EVIDENCE 4. Laryngoscope, 127:E42-E49, 2017.