PALLIDAL ACTIVITY DURING DYSTONIA - SOMATOSENSORY REORGANIZATION AND CHANGES WITH SEVERITY

A woman with progressive, medically intractable right upper Limb dysto nia underwent a pallidotomy with only transient improvement. During th e procedure her dystonia became more severe as she repeatedly made a f ist to command in order to provoke dystonia transiently (movement prov oked dystonia). Comparisons within cells in the internal segment of th e globus pallidus (Gpi) disclosed that the firing rate was the same at rest, with making a fist, and during movement provoked dystonia. Howe ver, the firing rate compared between cells decreased significantly th roughout the procedure as the patient made a fist repeatedly. During t he second half of the procedure the firing rate of cells in the Gpi wa s similar to that in hemiballismus. The proportion of cells in the GPi which responded to sensory stimulation was significantly higher in dy stonia (53%) than in hemiballismus (13%). These results suggest that p allidal activity can correlate inversely with the severity of dystonia , perhaps due to activity dependent changes in neuronal function resul ting from repeated voluntary movement.