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Pallidotomy increases cortical inhibition in Parkinson's disease
A Strafella1, P Ashby, A Lozano
1Division of Neurology, Playfair Neuroscience Unit, University of Toronto, Ontario, Canada.
Background:
Pallidotomy helps parkinsonian symptoms. We tested the hypothesis that this might be due to changes in inhibition in the motor cortex.
Methods:
We examined 15 patients with parkinsonism before and after posteroventral pallidotomy. Magnetic stimuli were delivered over the motor cortex, while subjects maintained a 30% maximum voluntary contraction of the contralateral first dorsal interosseus (FDI).
Results:
Weak stimuli inhibited voluntary muscle activity, while slightly stronger stimuli caused short latency facilitation from activation of the corticospinal neurons. After pallidotomy magnetic stimulation, at the threshold for the short latency facilitation, resulted in more inhibition than before.
Conclusion:
Pallidotomy increases cortical inhibition. This may be associated with improved control of movements.