Axial versus distal motor impairment in Parkinson's disease.

We measured axial (head rotation) and distal (wrist flexion and extension) movements in parkinsonian patients with varying stages of disability, before and after administration of L-dopa. Velocities for both movements were proportionately reduced in all stages of disease. L-Dopa administration provided a small but consistent increase in distal movement velocity for most patients, whereas in patients with advanced disease (stages III to V), axial movement velocity actually declined after administration of L-dopa. This decline may be partially responsible for the failure of L-dopa administration to reverse the loss of "righting reflexes" in these patients. Measurement of axial motor control may be a useful tool in evaluating therapeutics for Parkinson's disease patients.