Risk factors for underlying bilateral vestibular weakness in cochlear implant candidates

Cochlear implantation (CI) is associated with postoperative vestibular dysfunction in the implanted ear; however, limited data on baseline vestibular function in these patients exists. Bilateral vestibular weakness is associated with detrimental effects on quality of life. As such, it is important to identify patients with a preexisting bilateral weakness and consider this information in surgical planning.

Retrospective cohort study of the CI candidate population. All patients underwent routine preoperative vestibular evaluation, irrespective of symptoms.

Of 180 preoperative videonystagmographies, 39.4% showed vestibular weakness determined by caloric testing. Of these, 26.8% exhibited bilateral weakness. Patients with bilateral weakness had higher body mass index (31.6 kg/m²) than those with unilateral weakness or normal function (26.2 and 27.4 kg/m², P = 0.007). Further analysis of the audiologic data in the worse-hearing ear revealed worse hearing at 250, 500, and 1000 Hz (P < 0.05). Hearing threshold of 60 dB or worse at 250 Hz was the best prognostic indicator for bilateral weakness. At a threshold of 60 dB at 250 Hz, all patients with bilateral weakness are captured (100% sensitivity), with a specificity of 34.5%.

More than one-third of CI candidates have some degree of underlying vestibular dysfunction and 10.5% exhibit preexisting bilateral weakness. This study indicates that audiologic data may be a useful prognostic indicator of preexisting bilateral vestibular weakness. Given the well-documented detrimental effects of bilateral vestibular weakness on quality of life, we recommend that all patients who meet this cutoff undergo vestibular testing to assess for an underlying weakness.