Botulinum toxin to treat upper-limb spasticity in hemiparetic patients: analysis of function and kinematics of reaching movements.

Background: Poor control of reaching in spastic hemiparetic patients could be because of a combination of poor individuation of joints, weakness, spasticity, and/or sensory loss.

Objective: To assess the effect of botulinum toxin injections (BTIs) on spasticity, upper-limb function, and kinematics of reaching movements in patients with spastic hemiparesis caused by brain injury.

Methods: Fifteen patients with spastic hemiparesis and 9 healthy controls were included in this single-site, open-labeled study. The trajectories of reaching movements were recorded, and kinematic variables were computed. A clinical evaluation included the Motor Activity Log, the Action Research Arm Test (ARAT), and the Box and Block Test (BBT). Patients were assessed before (M0), 1 month after a first (M1), and 1 month after a second BTI (M4, at 4 months) in proximal and distal muscles.

Results: Significant differences were found between hemiparetic patients and healthy participants for all kinematic parameters. All parameters tended to improve after BTI. This effect was significant for velocity and smoothness. Functional scores also tended to improve. Improvements were greater at M4 than at M1, although the differences were not significant.

Conclusions: Kinematic parameters improved following BTI, without significant changes in clinical outcomes such as ARAT and BBT. The decrease in spasticity alone does not seem to explain the results, which may be a result of adaptation to the decrease in hypertonicity leading to increased use of the arm and possibly an increase in antagonist muscle strength.