GAMMA-KNIFE PALLIDOTOMY IN ADVANCED PARKINSONS-DISEASE

Posteroventral pallidotomy as a treatment for Parkinson's disease (PD) has been the subject of increasing interest. We treated 4 nondemented patients with advanced PD, 2 with severe bradykinesia and a declining response to medication, and 2 with marked clinical fluctuations. All patients received 180 Gy delivered in one sitting to the right postero ventral pallidum site, used by Laitinen and colleagues, adjusted as ne eded, to avoid the optic tract. Only 1 patient changed significantly. Dyskinesia completely resolved on the side contralateral to the lesion in this patient. This same patient also became transiently demented a nd psychotic. The other 3 patients suffered no clearly identifiable be neficial or harmful effects. Follow-up magnetic resonance imaging scan s of the brain at 1 year revealed lesions exactly where targeted altho ugh of unequal sizes. Our negative experience forces us to conclude th at either larger volumes of tissue must be ablated, that physiologic m onitoring is required for placing a lesion, that our subjects were poo r candidates for the procedure, or that surgical ablation and radiatio n cause tissue damage of different types with different results.