Neuronal activity in the globus pallidus in primary dystonia and off-period dystonia.

Decreased neuronal activity and altered firing patterns in the globus pallidus have been commonly observed in primary dystonia. Intraoperative neuronal recording in a patient with off-period dystonia revealed that the mean firing rates were considerably low in both the internal and external segments of the globus pallidus and that firing was irregular in the internal segment of the globus pallidus when dystonia developed, as compared with firing patterns in off-state parkinsonian patients without dystonia. These altered firing patterns were immediately reversed to those of off-state parkinsonism after relief of dystonia. These results suggest that primary dystonia and off-period dystonia result from the same physiological change in the basal ganglia. Ablation and stimulation of the internal segment of the globus pallidus can abolish both types of dystonia by blocking the abnormal activity of pallidal neurons.