Deep Brain Stimulation in Patients With 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 evaluate the safety and efficacy of STN DBS for dystonia. Up to 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 scale Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), and a
patient questionnaire will be administered postoperatively to determine if patients are
experiencing stimulation-induced motor adverse effects and will be logged for safety
monitoring. 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.

Inclusion Criteria:

- Refractory primary dystonia diagnosed by a movement disorders neurologist

- Severe functional impairment despite optimal medical management, including failed
botulinum toxin therapy

- Age 7-80 years (UCSF patients) and 18-80 (VA patients)

Exclusion Criteria:

- Patients considered at high risk for elective neurosurgery because of co-morbid
conditions

- Brain MRI showing extensive brain atrophy or small vessel ischemic disease

- Pregnancy

- Inability to tolerate awake microelectrode-guided neurosurgery

- Inability to follow up with post-operative study visits

- Inability to speak or read English

- Patients with a score of 4.5 or lower on the BFMDRS movement scale

- Patients with Secondary dystonia