Sequence of electrode implantation and outcome of deep brain stimulation for Parkinson's disease

IntroductionThe effect of the variability of electrode placement on outcomes after bilateral deep brain stimulation of subthalamic nucleus has not been sufficiently studied, especially with respect to the sequence of hemisphere implantation.MethodologyWe retrospectively analysed the clinical and radiographic data of all the consecutive patients with Parkinson's disease who underwent surgery at our centre and completed at least 1 year follow-up. The dispersion in electrode location was calculated by the square of deviation from population mean, and the direction of deviation was analysed by comparing the intended and final implantation coordinates. Linear regression analysis was performed to analyse the predictors of postoperative improvement of the motor condition, also controlling for the sequence of implanted hemisphere.Results76 patients (mean age 58±7.2 years) were studied. Compared with the first side, the second side electrode tip had significantly higher dispersion as an overall effect (5.6±21.6 vs 2.2±4.9 mm2, p=0.04), or along the X-axis (4.1±15.6 vs 1.4±2.4 mm2, p=0.03) and Z-axis (4.9±11.5 vs 2.9±3.6 mm2, p=0.02); the second side stimulation was also associated with a lower threshold for side effects (contact 0, p