Deep Brain Stimulation in Patients With Dystonia (STN DBS)

• The primary outcome measure is the change in Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) movement score from baseline to 12 months. [ Time Frame: 36 months ] [ Designated as safety issue: No ]
  

Device: Medtronic implantable deep brain stimulation (DBS) system
surgical placement of deep brain stimulation system for treatment of dystonia

Dystonia is an uncommon brain disorder in which there is abnormal muscle tone producing twisting, writhing movements and abnormal postures. It is associated with abnormal electrical activity in two groups of nerve cells in the brain called the globus pallidus internus (GPi) and the subthalamic nucleus (STN). Deep brain stimulation (DBS) has been shown to be an effective treatment in patients with medically refractory dystonia and is currently approved for both the GPi and STN targets under a humanitarian device exemption (HDE) for use in segmental and generalized primary dystonia as well as focal cervical dystonia. GPi DBS appears to be effective for medication-refractory focal and segmental dystonia affecting the cranial and cervical regions in open-label series, but recently GPi stimulation has been associated with subtle motor disturbances in previously non-dystonic body regions (i.e., arms and legs) in this population of patients. DBS of the STN has also been reported to be effective for treating generalized and cervical dystonia in small open label trials. STN DBS for cranial and cervical regions may provide similar efficacy in the treatment of dystonia as GPi DBS, but without unwanted stimulation-induced motor effects. Objectives of this study are to 1) evaluate the safety and efficacy of STN DBS for dystonia; 2) determine the time course of STN potential efficacy and optimal stimulation parameters; and 3) determine the frequency and severity of stimulation-induced motor adverse effects in previously non-dystonic body regions. Twenty-five patients will be screened, consented, and enrolled in this study. All patients will undergo bilateral STN DBS for dystonia. Participants will be evaluated pre- and postoperatively with standard dystonia rating scales including the Burke-Fahn-Marsden Dystonia rating scale (BFMDRS), Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), the Jankovic Rating Scale (JRS), and Clinical Global Improvement (CGI) rating scale. Changes in cognitive function will be assessed with neuropsychological testing. Stimulation parameters will be documented, and a patient questionnaire will be administered postoperatively to determine if patients are experiencing stimulation-induced motor adverse effects. Patient weight will be recorded at study visits. This pilot study will provide preliminary open label efficacy outcomes for STN DBS in the treatment of primary dystonia and will help determine if this target should be compared to GPi DBS in a larger double-blind trial.