Dynamic imbalance in gait ataxia. Characteristics of plantar pressure measurements.

The present study was designed to evaluate the interaction between disequilibrium and irregular stepping components of ataxic gait. For this purpose, we compared the walking patterns of patients with cerebellar dominant multiple system atrophy (MSAc, n = 8), spinocerebellar ataxia type 6 (SCA6, n = 4) and 16q-linked autosomal dominant cortical cerebellar atrophy (16q-linked ADCA, n = 6), and 6 normal subjects, by measuring toe and heel plantar pressures. In healthy subjects, the heel contacted the floor at step-in followed by an immediate shift of the center of pressure (COP) to the contacted leg. In ataxic gait, however, both the heel and toes simultaneously contacted the floor and the disappearance of the immediate shift of the COP was noted. These changes appeared to be nonspecific compensations for the instability. Examination of two parameters of ataxia-specific changes showed that prolongation of the double support period was associated with proportionate increase in the coefficients of variance of the plantar pressures and the step lengths on walking of patients with SCA6, but not those with MSAc and 16q-linked ADCA. Our results suggest that disequilibrium and irregularity are two separate and independent components of cerebellar ataxic gait.