Deep brain simulation of the globus pallidus pars interna in advanced Parkinson's disease

Pallidotomy is now widely performed for the treatment of advanced Parkinson 's disease (PD). Preliminary reports of the effect of globus pallidus pars interna deep brain stimulation (GPi DBS) have also been promising. We have analyzed a cohort of 22 consecutive patients enrolled in a multicenter stud y. Surgery was bilateral in I? and unilateral in five patients. At B-month follow-up, the bilaterally GPi-implanted patients demonstrated a marked imp rovement when examined after drug withdrawal ("off") and under optimal medi cation ("on") using the Unified Parkinson's Disease Rating Scale (UPDRS). T he benefit induced by the stimulation in the "off" medication condition in the total motor score was 31% and in the activities of daily Living (ADL) s cores was 39%. During the "on" medication period, the reduction in the tota l "on" dyskinesias score was 66% and in the ADL score was 32%. A similar pa ttern of improvement was seen in the group of patients with unilateral GPi stimulation, although a second cohort of 12 patients not included in the mu lticenter study showed greater improvements in "on" motor functioning. Alth ough the effect of DBS is predominantly reversible, electrode insertion alo ne resulted in measurable clinical effects in the absence of stimulation. T hus, at B-month follow-up,the benefit observed without stimulation was up t o 44% in the "on" dyskinesias score and 29% in timed tapping scores underta ken in the "off" medication state. Complications among 34 patients from all centers included perioperative infection (n = 3), hardware fracture (n = 2 ), and premature battery failure (n = 3). These results show a positive ant iparkinsonian effect of pallidal DBS. No specific complications were observ ed with bilateral procedures.