This study will evaluate the effectiveness of deep brain stimulation (DBS) for treating primary dystonia. Patients with dystonia have muscle spasms that cause uncontrolled twisting and repetitive movement or abnormal postures. Medical therapies are available, but not all patients get adequate relief from the abnormal movements or the pain associated with them. DBS is a surgical procedure that interrupts neuronal circuits in the globus pallidus interna (Gpi) and subthalamic nucleus (STN) - areas of the basal ganglia of the brain that do not work correctly in patients with dystonia. This results in decreased movement and therefore may lessen patients' symptoms and pain. The study will also examine the physiology of dystonia and determine whether the treatment effects of DBS in the Gpi differ significantly from DBS of the STN.

Patients 18 years of age and older with primary cervical dystonia that does not respond to medical treatment or botulinum toxin (Botox) may be eligible for this study. Candidates are screened with blood and urine tests, chest x-ray, electrocardiogram, and magnetic resonance imaging (MRI, see below) of the brain.

Each participant undergoes the following tests and procedures:

• Magnetic resonance imaging. This procedure is done after implantation of the stimulators to verify position of the electrodes. MRI uses a magnetic field and radio waves to produce images of the brain. The patient lies on a table that is moved into the scanner (a narrow cylinder), wearing earplugs to muffle loud knocking and thumping sounds that occur during the scanning process. The procedure usually lasts about 45 to 90 minutes, during which the patient is asked to lie still for up to 15 minutes at a time.
• Transcranial magnetic stimulation. This procedure maps brain function. A wire coil is held on the scalp, and a brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. During the stimulation, the patient may be asked to tense certain muscles slightly or perform other simple actions. The stimulation may cause a twitch in muscles of the face, arm, or leg, and the patient may hear a click and feel a pulling sensation on the skin under the coil. During the stimulation, electrical activity of muscles is recorded with a computer, using electrodes attached to the skin with tape.
• Neurologic evaluation. Before and after DBS, the patient's dystonia is measured with a standardized rating scale called the Toronto Western Spasmodic Torticollis Scale (TWSTRS).
• DBS treatment. Patients are randomly assigned to have electrodes implanted in either the Gpi or STN area of the basal ganglia. The electrodes are what stimulate the brain in DBS therapy. Before surgery, a frame is secured to the patient's head, and an MRI scan is done. DBS involves making two small incisions and two small holes in the skull, opening the lining around the brain, locating the Gpi or STN, securing the electrodes in place, and connecting them to the pulse generator that is placed under the skin below the collar bone. In addition, during the surgery, the patient is asked to move certain muscles. The muscle activity is recorded to gain a better understanding of the physiology of movement. After surgery, MRI scans are done to confirm placement of the electrodes.
• Stimulation and evaluation. After surgery, patients' movements are evaluated during and after stimulation. The changes in movement and function are videotaped and scored according to a rating scale. The optimal stimulation settings are determined and the stimulators are adjusted accordingly.

Neurologic evaluations with the TWSTRS scale are repeated at 1, 2, 3, 6 and 12 months after surgery, and the stimulators are adjusted as needed. Some of the evaluations are videotaped.