Early versus delayed bilateral subthalamic deep brain stimulation for Parkinson’s disease: Need for long-term trials.

We read with interest a recently published decision analysis on the timing of subthalamic nucleus (STN) deep brain stimulation (DBS) implants in Parkinson’s disease(PD).1 This model predicts that performing STN DBS in patients with less than 20% off time is associated with increased quality-adjusted life expectancy, compared with patients with more than 40% off time. We recently reported a cohort of PD patients treated with STN DBS 8 years previously 2 and found remarkable interindividual variability of outcome and variable response of different PD motor symptoms to DBS. At 8 years, rigidity and tremor improved more than gait and even more than limb akinesia, whereas speech did not improve and postural stability worsened.2 Furthermore, we observed between-patient variability of outcome at 8 years, raising the issue of differentiating PD subtypes who can best benefit from STN DBS. The simulation by Espay and colleagues1 is generally in keeping with our findings, but it did not consider UPDRS motor score subitems, which are part of the clinical evaluation of PD patients. The total UPDRS motor score does not allow details to be obtained on individual motor items that are subject to specific variations in the long term. The complexity of real-life scenarios, which also take into account clinical heterogeneity (eg, disease progression),3,4 cannot be easily reproduced by simulation models. We believe that long-term randomized controlled trials remain the gold standard for decision making on PD surgery and for the development of guidelines.