Long Term Changes in Parkinson’s Disease Patients Treated with Subthalamic Nucleus Deep Brain Stimulation : Clinical and Stimulation Parameters Changes

Th e use of chronic bilateral subthalamic nucleus stimulation has become increasingly widespread in the treatment of Parkinson’s disease (PD). Its benefi cial eff ects have been well documented. These effects include improvement in motor function and reduction of required dopaminergic medication, with resulting reduction or elimination of dyskinesias. Specifi c information regarding the durability of these results, however, has been relatively limited. Information regarding necessary changes to stimulation parameters over a long-term follow-up period is even sparser. Thirty consecutive patients who underwent placement of bilateral subthalamic nucleus deep brain stimulators were followed prospectively at six month postoperatively (baseline), and then again at one, three, and five years after surgery. Unifi ed PD Rating Scale (UPDRS) motor scores and dopaminergic medication requirement were recorded, as were the following stimulation parameters: amplitude, impedance, rate, pulse-width, and total current output. The patients’ motor function worsened slightly from mean score of 7.4 at baseline to 11.8 at five-year follow-up. During this period, total daily L-Dopa equivalent medication requirement did not change significantly (537mg to 678mg). There was no statistically signifi cant change in stimulation amplitude or pulse width. Overall current output increasedand impedance declined. Th is study has demonstrated that chronic subthalamic nucleus stimulation continues to provide good control of the motor symptoms of PD. Although the motor scores increasedduring the follow-up period, this increase was relatively minor and these scores remained comparatively low. Increase in average medication dosage was not necessary to maintain good control. Stimulation settings remained well within the limitations of the pulse generator device, indicating the potential for continued efficacy in the future.