Gait initiation characteristics in elderly patients with unilateral vestibular impairment

The study tested the hypothesis that vestibular patients (n=14) with chronic unsteadiness caused by a documented peripheral unilateral vestibular dysfunction would display differences in muscular activation and movement pattern during gait initiation compared to age-, gender- and body-size-matched healthy Controls (n=14). The displacements of the whole body Center of Pressure (CoP) during the preparatory phase before the swing leg is lifted, were markedly different in vestibular patients. The backward shift during this phase was significantly smaller than in Controls, coupled with a larger secondary corrective forward shift of the CoP. Conversely, the CoP-shift in the M-L direction towards the stance leg was larger in the vestibular patients. Most vestibular patients lacked the anticipatory tibialis anterior (TA) burst, which normally is a prerequisite for the backward displacement of the CoP that precedes the forward movement. The vestibular patients displayed more pronounced TA-Gastrocnemius coactivation in the stance leg when the swing leg was lifted. The duration of the preparatory phase was significantly longer in vestibular patients than in Controls, with no time differences in the later gait initiation events. The vestibular patients started from a more symmetrical stance and with less M-L variation than the Controls. It is concluded that chronically impaired vestibular function leads to a different strategy to create forward momentum to the body. In addition, there is evidence that vestibular patients have diminished postural stability, or alternatively a more cautious behaviour, when initiating the second step.