Bilateral Vestibular Hypofunction in Quantitative Head Impulse Test: Clinical Characteristics in 23 Patients.

OBJECTIVE To explore clinical features of patients with bilateral vestibular hypofunction (BVH) verified in motorized head impulse test (MHIT). MATERIALS AND METHODS We examined clinical records of 23 adult patients (10 males and 13 females), whose gain of the vestibulo-ocular reflex in the MHIT was bilaterally lowered. Fifteen of 62 unilateral cochlear implant (CI) recipients routinely tested both pre- and postoperatively with the MHIT had BVH. Eight of 198 vestibular outpatients selected to the MHIT due to clinical causes had BVH. Clinical characteristics and a questionnaire regarding current sensations were analyzed. RESULTS The mean gain±SD in the MHIT was 0.26±0.17 on the right and 0.26±0.14 on the left side. The mean gain in the CI recipients did not differ from that of vestibular outpatients (p>0.05). All outpatients with BVH suffered from oscillopsia, whereas only 46% of CI recipients experienced oscillopsia (p=0.048). Instability was more prominent (p=0.004) and quality of life further decreased (p=0.012) among vestibular outpatients compared with CI patients. Most common etiology for the BVH was meningitis. Other causes were either sudden or progressive loss of labyrinthine function, bilateral Meniére's disease, and ototoxicity. CONCLUSION BVH is rare even in a specialized clinic. Vestibular outpatients were more disabled than CI recipients with the BVH.