Locomotion speed determines gait variability in cerebellar ataxia and vestibular failure.

Temporal gait variability is a critical parameter in patients with balance problems. Increased magnitude of temporal gait variability corresponds to a higher risk of falls. The purpose of this study was to investigate the influence of walking speed on temporal stride-to-stride variability in patients with cerebellar and vestibular deficits. A GAITRite system was used to analyze the gait of 40 patients with cerebellar ataxia, 22 patients with bilateral vestibular failure, and 51 healthy subjects over the entire range of the individual's speed capacity. The coefficient of variability of stride time was calculated for each walk. Temporal gait variability was increased in cerebellar patients and vestibular patients. The magnitude of this variability depended on walking speed in a disease-specific manner. In patients with cerebellar ataxia, variability was increased during slow (8.4 ± 5.3%, P < .01) and fast (7.9 ± 6.4%, P < .01) walking speed but was normal during preferred walking speed. This resulted in a speed-related U-shaped function of stride-time variability. Patients with vestibular failure had increased variability during slow walking (9.9 ± 4.3%, P < .01). During walking with medium and fast walking speed, stride time variability was normal. Minimal temporal gait variability appears to be attractive for the locomotor system in cerebellar patients because these patients preferred to walk at a velocity associated with minimal stride-time variability. In contrast to previous studies, vestibular patients accelerate rather than decelerate gait to achieve dynamic stability. This may be explained by reduced sensory integration during fast locomotion.