Pre-habilitation Before Vestibular Schwannoma Surgery—Impact of Intratympanal Gentamicin Application on the Vestibulo-Ocular Reflex

Abstract

Background: Patients with vestibular schwannoma that show residual peripheral-vestibular function before surgery may experience sudden and substantial vestibular loss of function after surgical resection. To alleviate the sudden loss of peripheral-vestibular function after vestibular-schwannoma (VS) resection, pre-surgical intratympanic gentamicin application was proposed.Objective: We hypothesized that this approach allows for a controlled reduction of peripheral-vestibular function before surgery but that resulting peripheral-vestibular deficits may be canal-specific with anterior-canal sparing as observed previously in systemic gentamicin application.Methods: Thirty-four patients (age-range = 27–70 y) with unilateral VS (size = 2–50 mm) were included in this retrospective single-center trial. The angular vestibulo-ocular reflex (aVOR) was quantified before and after (29.7 ± 18.7 d, mean ± 1SD) a single or two sequential intratympanic gentamicin applications by use of video-head-impulse testing. Both aVOR gains, cumulative saccadic amplitudes, and overall aVOR function were retrieved. Statistical analysis was done using a generalized linear model.Results: At baseline, loss of function of the horizontal (20/34) and posterior (21/34) canal was significantly (p < 0.001) more frequent than that of the anterior canal (5/34). After gentamicin application, loss of function of the horizontal (32/34) or posterior (31/34) canal remained significantly (p ≤ 0.003) more frequent than that of the anterior canal (18/34). For all ipsilesional canals, significant aVOR-gain reductions and cumulative-saccadic-amplitude increases were noted after gentamicin. For the horizontal canal, loss of function was significantly larger (increase in cumulative-saccadic-amplitude: 1.6 ± 2.0 vs. 0.8 ± 1.2, p = 0.007) or showed a trend to larger changes (decrease in aVOR-gain: 0.24 ± 0.22 vs. 0.13 ± 0.29, p = 0.069) than for the anterior canal.Conclusions: Intratympanic gentamicin application resulted in a substantial reduction in peripheral-vestibular function in all three ipsilesional canals. Relative sparing of anterior-canal function noted at baseline was preserved after gentamicin treatment. Thus, pre-surgical intratympanic gentamicin is a suitable preparatory procedure for reducing the drop in peripheral-vestibular function after VS-resection. The reasons for relative sparing of the anterior canal remain unclear.

Subjective perception of activity level: A prognostic factor for developing chronic dizziness after vestibular schwannoma resection?

“…Different treatments can be considered, of which observation with annual follow-up, resection surgery and radiosurgery or therapy are the most prevailing options (3-5). A VS resection causes an acute unilateral vestibular deafferentation so that postoperative symptoms such as acute dizziness, unsteadiness, and nausea may occur to a greater or lesser extent, depending on the residual vestibular function before surgery (6)(7)(8)(9)(10). In case of sudden vestibular function loss, central vestibular compensation is expected to take place after the acute phase, leading to a balanced sensory reweighting and resolution of the majority of the symptoms (11,12).…”

Pre-habilitation with intratympanic gentamicin in vestibular schwannomas: a systematic review

“…While we accept the limitations of the existing studies, it appears that ablation of vestibular function achieves compensation before surgery and speeds up recovery. There is some risk of hearing loss with intratympanic gentamicin injections, 20 but this risk must be weighed against the benefit of recovery. This is especially so if patients already have significant hearing loss or are undergoing translabyrinthine surgical resection of their vestibular schwannomas, because the gentamicin would not add any additional morbidity, particularly if no hearing-preservation surgery is being considered.…”

Intratympanale Medikamentenapplikation – Indikationen und Ablauf

“…Durch kontrollierte, schrittweise präoperative Gentamicin-induzierte Ablation der ipsilateralen peripher-vestibulären Funktion können bereits präoperativ Adaptationsund Habituationsprozesse einsetzen, und somit kann postoperativ eine schnellere Rehabilitation erreicht werden [19]. Postoperativ sind die klinischen Symptome des unilateralen Vestibularisausfalls geringer, und die Mobilität der Patienten ist besser [20]. Entsprechend gibt es vom Kongress für Neurochirurgie die Level-3-Empfehlung, dass eine präoperative intratympanale Gentamicin-Ablation des Vestibularapparats erwogen werden sollte [21].…”