Subthalamic stimulation for cervical dystonia.

Abstract

The globus pallidus internus (GPi) has been the primary target for deep brain stimulation (DBS) to treat severe medication-refractory dystonia. Some patients with primary cervical dystonia do not respond adequately to GPi stimulation. Subthalamic nucleus (STN) DBS may provide an alternative choice for treating this dystonia. In this study, we analysed the effect of bilateral STN DBS on two patients of medically refractory primary cervical dystonia. The severity of the dystonia was measured using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) preoperatively, and 1, 3, 6 and 12months postoperatively and yearly follow-up was performed. Any change in mental status was recorded using the Mini-Mental State Examination (MMSE) score. Surgery was performed using the Leksell stereotactic system and by fusing CT scan and MR images with neuronavigation and microelectrode recording. Both patients were followed for more than 3years. STN DBS was well-tolerated by both patients with no adverse effects. The benefit seems to be immediate. The first patient showed 74% improvement, and the second patient showed 84.3% improvement in the overall TWSTRS score. No mental deterioration was observed in either of the cases, as the MMSE score remained unchanged in both patients. A prior bilateral pallidal lesion in the first case did not adversely affect the outcome. This study showed that bilateral STN DBS results in a very significant improvement in cervical dystonia with no mental worsening and suggests that STN DBS may be an alternative to GPi DBS for treating primary cervical dystonia.