Prevalence and risk factors for underlying vestibular weakness in cochlear implant candidates

Abstract

Objective: To describe the baseline vestibular function in cochlear implant candidates and identify demographic and audiologic risk factors for vestibular dysfunction. Study design: Retrospective cohort study (2012–2022) of the CI candidate population. Setting: Neurotology practice at large academic hospital. Methods: All patients evaluated for CI underwent routine preoperative vestibular evaluation, irrespective of symptoms. Preoperative audiologic data was also analyzed. Results: Of a total of 180 preoperative VNGs obtained, 39.4% demonstrated preoperative vestibular weakness as determined on caloric testing. Of these, 26.8% had evidence of bilateral weakness, 60.5% unilateral weakness ipsilateral to the worse hearing ear and 12.7% contralateral weakness. Demographic variables such as age, gender, BMI and medical comorbidities including diabetes, hypertension, hyperlipidemia were not found to be associated with a higher risk of vestibular weakness. Patients with vestibular weakness had significantly poorer low tone hearing. Hearing loss at 250 Hz was the strongest prognostic factor for risk of vestibular weakness. Using a cutoff of 45dB at 250 Hz as an indicator for obtaining preoperative VNG was found to have a sensitivity of 92.9% and specificity of 37.9% for identifying vestibular weakness. Conclusions: Traditional CI candidates have a high prevalence of preoperative vestibular weakness. Audiologic data and specifically severity of hearing loss in the low frequencies may be a useful indicator of vestibular weakness and thus help guide which patients should undergo preoperative VNG. We propose the cutoff point of 45dB at 250 Hz as an indicator of higher risk for vestibular weakness and recommend preoperative VNG testing for this population prior to surgery.