CORTICAL MOTOR OVERACTIVATION IN PARKINSONIAN-PATIENTS WITH L-DOPA-INDUCED PEAK-DOSE DYSKINESIA

We have studied the regional cerebral blood flow (rCBF) changes induce d by the execution of a finger-to-thumb opposition motor task in the s upplementary and primary motor cortex of two groups of parkinsonian pa tients on L-dopa medication the first one without L-dopa induced dyski nesia (n = 23) and the other with moderate peak-dose dyskinesia (n = 1 5), and of a group of 14 normal subjects. Single photon emission tomog raphy with i.v. Xe-133 was used to measure the rCBF changes. The dyski netic parkinsonian patients exhibited a pattern of response which was markedly different from those of the normal subjects and non-dyskineti c parkinsonian patients, with a significant overactivation in the supp lementary motor area and the ipsi-and contralateral primary motor area s. These results are compatible with the hypothesis that an hyperkinet ic abnormal involuntary movement, like L-dopa-induced peak dose dyskin esia, is due to a disinhibition of the primary and associated motor co rtex secondary to an excessive outflow of the pallidothalamocortical m otor loop.