Kinematic aiming task: measuring functional changes in hand and arm movements after botulinum toxin-A injections in...

To describe different aspects of a kinematic aiming task (KAT) as a quantitative way to assess changes in arm movements within 2 wks after botulinum toxin-A (BTX-A) injections in children with spastic hemiplegia.

Intervention study randomized clinical trial; follow-up within 4 wks after baseline measurement.

The KAT gave a high intraclass correlation on movement time, spread of end points (END), and index of performance effective (IP-E). After BTX-A, a significant increase of END and IP-E was shown if precision demand in the KAT was high, whereas the inverse occurred when speed was more important. These functional changes coincided with a significant decrease of the maximum voluntary contraction of the flexor muscles of the forearm. Muscle tone measured with the Ashworth scale did show a nonsignificant decrease of muscle tone, as did the stretch restricted angle and the active and passive ranges of motion of the elbow and wrist.

Muscle force decreased immediately after BTX-A, showing the direct effect of BTX-A. The KAT is an adequate, reproducible way to quantify functional changes after BTX-A in the upper limb. BTX-A has an inverse effect in the precision task when accuracy is important, and it has a positive effect when speed prevails.