Objective: To examine objectively the clinical effects of subthalamic nucleus (STN) deep brain stimulation (DBS) in advanced PD.
Methods: Our initial seven consecutive patients with medication-refractory motor fluctuations and levodopa-induced dyskinesias undergoing chronic STN DBS underwent a standardized preoperative evaluation followed by a 2-day double-blind evaluation of efficacy 6 to 12 months after electrode implantation. Diaries documenting motor fluctuations and dyskinesias were also completed preoperatively and postoperatively.
Results: In the medication-off state, turning the stimulators on resulted in improvement in mean total Unified Parkinson's Disease Rating Scale (UPDRS) motor score by 58% including the following improvements in composite scores: akinesia 57%, rigidity 52%, tremor 82%, and gait and postural stability 49%. Additionally, the medication-off state improved 17% without stimulation, possibly as a result of electrode insertion alone or carry-over of chronic stimulation. In the medication-on, stimulation-on state, all major features of parkinsonism improved and total UPDRS motor score improved 41% compared with before surgery. Activities of daily living were improved while off medication 30%, and levodopa-induced dyskinesias were reduced 83% while total drug dosage was decreased 40%. With chronic stimulation, patients reported that the percentage of time spent in the "on" state (without dyskinesias) increased from 26% to 52% and "off" time decreased from 30% to 6%. Operative complications including cognitive worsening were not uncommon.
Conclusions: STN DBS is a promising new surgical option for the treatment of advanced PD. The marked clinical benefits obtained in these severely disabled patients outweighed the adverse effects.