Galvanic-induced body sway in vestibular schwannoma patients: Evidence for stimulation of the central vestibular system

Objective - To investigate the various possible sites of excitation by galvanic stimulation by comparing the galvanic-induced body sway (GBS) in vestibular schwannoma (VS) patients with that in healthy subjects. Material and Methods - This was a prospective experimental study conducted in a tertiary referral centre. In a previous study we developed a standardized procedure for reproducible quantification of GBS using a monaural continuous 1-cosinusoidal stimulus (0.5 Hz; 2 mA). In this study, 23 VS patients were tested before and 12 VS patients were also tested after surgical intervention (extirpation of tumour with concomitant vestibular neurectomy) and the results were compared with those obtained in 47 healthy subjects. Results - There were no significant differences in mean total GBS gain between VS patients and healthy subjects (p >0.05) before surgical intervention. After vestibular neurectomy a significant difference in the mean total GBS gain was observed, but GBS was still present after surgery. Conclusion - These results prove that galvanic vestibular stimulation excites the central vestibular system even when conduction via the vestibular nerve is hampered.