Reader Response: Deep Brain Stimulation in Early-Stage Parkinson Disease: Five-Year Outcomes

We have followed with great interest the pilot trial on subthalamic nucleus deep brain stimulation (DBS) for early-stage Parkinson disease (PD). The 5-year outcomes of this trial were just published by Hacker et al.1 The authors argue that DBS reduces the risk of disease progression based on a reduced rest tremor when these patients are compared with patients who were randomized to only optimized drug therapy (ODT). Barring rest tremor, this follow-up study did not show significant difference between the ODT and DBS + ODT groups for on-therapy motor scores and measures of disability and quality of life. Although tremor can be bothersome to patients with early-stage PD, bradykinesia is clearly the disabling feature.2 Interestingly, the DBS + ODT group performance in the timed tests at 5 years1 and off-therapy bradykinesia at 2 years3 were worse, although not significant. Besides, progressive neurodegeneration may lead to gradual abatement of tremor, and tremor-dominant PD often transforms to akinetic-rigid PD.4 We certainly agree that early DBS can reduce the need of medications and possibly abolish the risk of developing dyskinesias or hallucinations in the long term. Nonetheless, we would recommend caution when stating a “Class II evidence that DBS implanted in early-stage Parkinson disease decreases the risk of disease progression”. Although similar between-group adverse event profiles were reported, 2 of the 15 DBS + ODT patients had potentially disabling adverse events: a perioperative stroke and an intracranial infection.5 In our opinion, with several variables to factor in, it is premature—and possibly dangerous—to conclude that DBS in early-stage PD reduces the risk of disease progression.

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