Voluntary movement after pallidotomy in severe Parkinson's disease

The mechanisms bradykinesia after investigated in 17 patients undergoing un ilateral pallidotomy for severe Parkinson's disease. Clinical ratings of 'o ff period bradykinesia demonstrated a maximal improvement of 22% 3 months p ostoperatively. Kinematic assessments of rapid repetitive finger and sequen tial arm movements were performed after overnight withdrawal of antiparkins onian medications. There was a bilateral reduction in the inter-onset laten cy of a two-stage sequential arm movement and a contralateral increase in s peed of arm movement after pallidotomy, There was no significant improvemen t postoperatively in the rhythm, amplitude or speed of repetitive finger mo vements. The results confirm the of improvement in parkinsonian posterovent ral pallidotomy were clinical impression that pallidotomy improves bradykin esia, This was more evident for complex limb movements, which used attentio nal strategies and external (visual and auditory) cues, than for repetitive finger-tapping movements, which were largely internally generated. Since a blation of the pallidum can only reduce inhibitory pallidal outflow it is u nlikely to restore the normal pallidal influence on thalamocortical motor c ircuits. Therefore, any improvement in bradykinesia after pallidotomy must be related to mechanisms other than restoration of pallidothalamocortical c onnectivity. Based on the above observations, we suggest that some of the c hanges in motor control may be explained by the greater efficacy of externa l cues in facilitating movement after withdrawal of the abnormal pallidal d ischarge.