Hearing and Vestibular Function After Preoperative Intratympanic Gentamicin Therapy for Vestibular Schwanomma as Part of Vestibular Prehab

OBJECTIVE:: To evaluate auditory and vestibular function after presurgical treatment with gentamicin in schwannoma patients. BACKGROUND:: The vestibular PREHAB protocol aims at diminishing the remaining vestibular function before vestibular schwannoma surgery, to ensure less acute symptoms from surgery, and initiate a more efficient vestibular rehabilitation already before surgery. However, the potential cochleotoxicity of gentamicin is a concern, since modern schwannoma surgery strives to preserve hearing. STUDY DESIGN:: Retrospective study. SETTING:: University hospital. PATIENTS:: Seventeen patients diagnosed with vestibular schwannoma between 2004 and 2011, and took part in vestibular PREHAB program. The patients were of age 21 to 66 years (mean 48.8), 9 females and 8 males. INTERVENTION:: Intratympanic gentamicin installations before surgery as part of the vestibular PREHAB. MAIN OUTCOME MEASURES:: Hearing thresholds, word recognition score, caloric response, subjective visual vertical and horizontal, cVEMP, and vestibular impulse tests. RESULTS:: Combined analysis of frequency and hearing threshold showed a significant decrease after gentamicin therapy (p <0.001). Pure-tone average decreased with 7.1 ± 8.5 dB (p = 0.004), and speech recognition with 10%. The treatment resulted in unilateral vestibular deafferentation with no notable reaction to bithermal caloric irrigation (reduction 64%, p <0.001), loss of the vestibulo-ocular response measured by the head-impulse test, and deviation of subjective horizontal/vertical to the side of the lesion (+2.2 degrees, p = 0.010). CONCLUSIONS:: Intratympanic installations of gentamicin, as part of the vestibular PREHAB, result in unilateral vestibular deafferentation, but constitute a definite risk for high-frequency hearing loss. The hearing results are in line with those reported upon when treating Menière’s disease.