Deep-brain stimulation (DBS) for Parkinson's disease (PD) received yet another endorsement with the recent publication of Deuschl and colleagues'1 large, randomised-pairs trial of subthalamic nucleus (STN) stimulation versus standard medical treatment. Despite many published studies of DBS in PD, few have been large, well controlled, or randomised using a medically treated control group for comparison. Furthermore, quality-of-life scales were used as the primary endpoint in Deuschl and colleagues' study in addition to standard motor scales for PD. Not surprisingly, surgically treated patients had substantially better outcomes at 6 months than did medically treated patients. In fact, improvements in scores on the Parkinson's disease questionnaire-39 after surgery were far greater than improvements in the scores noted in various clinical trials of antiparkinson drugs in which the questionnaire was used as a secondary response variable. Changes were understandably greatest in the motor aspects of the scale with little difference in the neurobehavioural components. Of note, in the paired analysis 36% of patients who received medical treatment showed greater improvements than their counterparts assigned DBS. Paired analysis of the off-medication motor component on the unified Parkinson's disease rating scale favoured the medically treated group in 27% ofpairs. Serious adverse effects, although infrequent, occurred more readily in the DBS group. Why did some of the medically treated patients do better than their DBS-treated counterparts and where should DBS now reside in the hierarchy of PD treatments?
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