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.