iPatax: a Tablet-based Tool for Quantitative Assessment of Cerebellar Ataxia

The clinical severity of cerebellar ataxia is still assessed primarily using ordinal rating scales, and continuous quantitative measures are still limited. In this context, we have developed iPatax, an iPad^®-based application, as a quantitative and objective tool for assessment of cerebellar motor dysfunction. Finger movements were recorded in 27 controls and 28 patients with cerebellar ataxia during three target-following tasks: non-continuous linear, non-continuous circular, and continuous circular movements. In the controls, the coefficient of variation of velocity (CVV) during non-continuous linear movements and the average distance from the target trajectory (AD) during non-continuous circular movement both improved over repeated trials, consistent with learning-related changes, and were prioritized as candidate metrics. Both metrics differentiated patients with cerebellar ataxia from controls (AUCs = 0.853 and 0.918, respectively). In the patients, CVV during non-continuous linear movement correlated significantly with both the total Scale for the Assessment and Rating of Ataxia (SARA) score and the upper-limb subscore (total SARA: r_S = 0.50; upper-limb subscore: r_S = 0.51), whereas AD during non-continuous circular movements correlated with the total SARA score but not with the upper-limb subscore (total SARA: r_S = 0.44; upper-limb subscore: r_S = 0.063). These findings suggest that, as a widely available tablet device, iPatax can capture and quantify clinically relevant temporal and trajectory-related aspects of cerebellar motor dysfunction. This approach may supplement current ordinal rating scales in clinical and research settings.