Abnormal activity in the globus pallidus in off-period dystonia.

Pallidotomy was performed in a parkinsonian patient with off-period foot dystonia. Dystonia appeared at the beginning of surgery and disappeared after the first microelectrode penetration of the globus pallidus, perhaps a micropallidotomy effect. Neuronal recording during dystonia revealed that the mean firing rates were 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, compared with firing patterns in offstate parkinsonian patients without dystonia. These firing patterns immediately changed into those of nondystonic, off-state parkinsonism after relief of dystonia These results suggest that off-period dystonia results from the same physiological change in the basal ganglia as that in primary dystonia.