Comparison of Different Exercise Programs in the Rehabilitation of Patients with Chronic Peripheral Vestibular Dysfunction

Abstract

The purpose of this study was to evaluate the effects of two exercise programs on balance performance in patients with chronic peripheral vestibular dysfunction and to assess whether these exercise programs induce adaptive modifications of the vestibulo-ocular reflex (VOR). Patients were randomly assigned to one of two groups. (1) Those in the Rehab (Reh) group (n=11) received a comprehensive exercise program that consisted of balance retraining and goal-directed eye-head exercises under combinations of varied visual and somatosensory sensory conditions. Patients received 45-minute training sessions, three times per week for 12 weeks, and were instructed on a custom home exercise program. (2) Those in the Home group (n=12) were instructed to perform the Cooksey-Cawthorne eye-head exercises at home, on a daily basis, for 12 weeks. In addition, after completion of the exercise program and a follow-up period, 7 of the participants in the Home group (here defined as the A group) chose to enter the Reh program (here defined as the B group). Balance performance was assessed by measuring the peak-to-peak magnitude and total amount of anterior-posterior body sway, and of horizontal (shear) ground reaction force during six test conditions, in which visual and somatosensory orientation cues were reduced or altered by rotation of the visual surround or support surface in proportion to the subject's sway, and in which vision was eliminated (eyes closed). The VOR response to step chair rotations of 60°/s and 120°/s, and the optokinetic reflex (OKN) response to 600/s constant velocity optokinetic stimuli were recorded. Left-right difference in VOR gain, VOR time constant, and OKN gain were determined. These tests were performed 1 day prior to start of treatment (TD 1), 6 weeks after start of treatment (TD 2), at the end of the 12-week treatment period (TD 3), and 5 months after end of treatment (TD 4). The findings revealed a significant improvement in standing balance performance under dynamic conditions for patients in the Reh program (Reh and B groups) but not for patients performing the eye-head exercise (Home or A groups). Thus, even inpatients with chronic vestibular dysfunction, compensation for the loss or disruption of peripheral vestibular inputs can be effectively induced by exercises that provide sensory feedback appropriate for behavioral changes involving sensory substitution or sensory-motor reorganization. In addition, a significant reduction in left-right differences in VOR gain was observed for the Reh group and B group (patients who performed exercises that involved eye and head movements where fixation on stationary and moving visual targets was a requirement), as compared to no change in the Home or A group (patients who performed eye and head oscillations where fixation was not a requirement). However, there was no significant change in left-right differences of the VOR time constant over the four test periods in any group. These results support the view that activities that produce error signals (ie, retinal image slip) that can be used to indicate the performance of the oculomotor system during head movements are required to facilitate recalibration of left-right differences in VOR gain.