Salient and placebo vibrotactile feedback are equally effective in reducing sway in bilateral vestibular loss patients

This study explores the effect of vibrotactile biofeedback on body sway in stance in patients with severe bilateral vestibular losses in a placebo-controlled study. A tilt sensor mounted on the head or trunk is used to detect head or body tilt and activates via a microprocessor 12 small vibrators that are placed around the waist with a mutual distance of 30°. Two positions of the tilt sensor (head and trunk) and three types of biofeedback (normal, full and random) were evaluated, besides no biofeedback. Body sway during stance was assessed in 10 patients with bilateral vestibular areflexia and performance was scored in the seven different conditions. Inter-individual and test-retest variability without biofeedback was assessed in 10 additional patients with bilateral vestibular areflexia. In six patients no significant change in body swaypath was observed using biofeedback. In four patients body swaypath decreased significantly using biofeedback and sensor on the head in all three activation modes, whereas with sensor on the trunk only one patient showed a significant improvement in swaypath in all three activation modes. The patients rated the functionality of the AVBF system and its effect on balance on average 6.5 on a scale from 0 to 10. Thus, body sway improved in 4 out of 10 patients using biofeedback, but the improvement with true biofeedback was only observed in those subjects where an improvement was present in placebo mode as well. The improvement was, at least partially, caused by other effects than biofeedback, like training, increased self-confidence or alertness