Abnormal activity in the globus pallidus in off-period dystonia

Pallidotomy was performed in a parkinsonian patient with off-period foot dy stonia. Dystonia appeared at the beginning of surgery and disappeared after the first microelectrode penetration of the globus pallidus, perhaps a mic ropallidotomy effect. Neuronal recording during dystonia revealed that the mean firing rates were low in both the internal and external segments of th e globus pallidus, and that firing was irregular in the internal segment of the globus pallidus, compared with firing patterns in off-state parkinsoni an patients without dystonia. These firing patterns immediately changed int o those of nondystonic, off-state parkinsonism after relief of dystonia. Th ese results suggest that off-period dystonia results from the same physiolo gical change in the basal ganglia as that in primary dystonia.