Postoperative gait deterioration after bilateral subthalamic nucleus stimulation in Parkinson's disease

Deep brain stimulation of the subthalamic nuclei (STN) is a good therapeutic option to reduce dyskinesias and improve appendicular motor signs in well-selected patients with advanced Parkinson's disease (PD). Concerns about long-term adverse effects play an increasingly role in the decision whether or not to refer patients for this treatment. Worsening of gait as a consequence of STN stimulation for PD has been described, but may be under-recognized in clinical practice. The aim of this study was to evaluate the effects of STN stimulation on gait relative to global outcome in a group of consecutively operated patients. For this purpose, we used a standardized patient questionnaire that asked about global outcome and specific effects on gait, as experienced both 6 months postoperatively and currently (at the time of completing the questionnaire; mean: 2.7 +/- 1.1 years). A delayed worsening of gait after bilateral STN stimulation was experienced by a considerable proportion of patients (42% of subjects, for gait in the OFF phase), and this was apparently relatively "selective" because their global outcome scores continued to be improved. These findings highlight the presence of a hitherto poorly recognized long-term complication of bilateral STN stimulation. Further systematic studies are required to pinpoint the clinical and surgical determinants of this late gait deterioration.