Habituation to galvanic vestibular stimulation

Objective - To examine the response decline that occurs upon repetitive galvanic vestibular stimulation (GVS) and hampers long-term clinical evaluations. 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 galvanic-induced body sway (GBS). The most reproducible responses were found using a continuous 1-cosinusoidal stimulus (0.5 Hz; 2 mA) preceded by a pre-habituating stimulus. This binaural prestimulation reduced the short-term (< 5 min) response decline to a non-significant level. The response decline without prestimulation was interpreted as habituation to the galvanic stimulation. In the present study we evaluated possible long-term habituation to GVS, which may hamper longitudinal clinical evaluations. Possible long-term habituation using the short-term habituating prestimulus concept was studied by quantifying GBS in 40 subjects at 5 consecutive time points. Subjects were subdivided into four equal groups who were tested with four different time intervals between the five measurements, ranging from 1 day to 2 weeks. Results - The absolute test results did not vary with the time interval (p = 0.217; repeated measurement test). Irrespective of the time interval between the tests, habituation occurred after the first stimulation and remained stable at all consecutive measurements. GVS habituation did not depend on either the degree of daily life activity (moderate practice of sport) or on gender. Conclusion - The current protocol, using a prehabituating binaural stimulus, showed that reproducible assessment of the GVS over a time course of days to weeks was possible starting from the second test.