Quantification of Upper-Extremity Movement Pattern in Patients with Stroke using Touchscreen: A Pilot Study.

Humans typically move slower if the movement needs to be more accurate. Such a tradeoff between movement speed and accuracy is quantified in Fitts' Law as a linear relationship between the movement time (MT) and the index of difficulty (ID). For patients with stroke, the detailed pattern of speed-accuracy tradeoff is likely affected due to disrupted neuromuscular control in stroke. In this study, we adapted a previously published iPad software program designed for the test of Fitts' Law in children with dystonia. Subjects were asked to touch targets with different sizes and distances on the touchscreen. Data from 3 patients with stroke suggest that the post-stroke upper-extremity movements still obey Fitts' Law, but the affected side showed larger slopes, and higher endpoint errors compared with the unaffected side. Moreover, the success rate in the affected side was significantly higher than healthy controls, but not than the unaffected side. Our preliminary data suggest that Fitts' Law provides a promising toolkit for quantitatively assessing the movement behavior in stroke.