Brain, Vol. 122, No. 5, 895-906,
May 1999
© 1999 Oxford University Press
Voluntary movement after pallidotomy in severe Parkinson's disease
1 University Department of Medicine, 2 Department of Neurology, 3 Department of Neurosurgery, Royal Adelaide Hospital, Adelaide, South Australia, Australia
Correspondence to:
Professor P. D. Thompson, University Department of Medicine, Royal Adelaide Hospital, Adelaide, South Australia 5000, Australia
The mechanisms of improvement in parkinsonian bradykinesia after posteroventral pallidotomy were investigated in 17 patients undergoing unilateral pallidotomy for severe Parkinson's disease. Clinical ratings of `off' period bradykinesia demonstrated a maximal improvement of 22% 3 months postoperatively. Kinematic assessments of rapid repetitive finger and sequential arm movements were performed after overnight withdrawal of antiparkinsonian medications. There was a bilateral reduction in the inter-onset latency of a two-stage sequential arm movement and a contralateral increase in speed of arm movement after pallidotomy. There was no significant improvement postoperatively in the rhythm, amplitude or speed of repetitive finger movements. The results confirm the clinical impression that pallidotomy improves bradykinesia. This was more evident for complex limb movements, which used attentional strategies and external (visual and auditory) cues, than for repetitive finger-tapping movements, which were largely internally generated. Since ablation of the pallidum can only reduce inhibitory pallidal outflow, it is unlikely to restore the normal pallidal influence on thalamocortical motor circuits. Therefore, any improvement in bradykinesia after pallidotomy must be related to mechanisms other than restoration of pallidothalamocortical connectivity. Based on the above observations, we suggest that some of the changes in motor control may be explained by the greater efficacy of external cues in facilitating movement after withdrawal of the abnormal pallidal discharge.
pallidotomy; Parkinson's disease; bradykinesia; movement; kinematic
ADL = activities of daily living; GPi = internal globus pallidus; IOL = inter-onset latency; SMA = supplementary motor area; UPDRS = unified Parkinson's disease rating scale
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