Pathophysiological Insights Into Deep Brain Stimulation for Primary Cervical Dystonia

• The body's response to Transcranial Magnetic Stimulation (TMS). [ Time Frame: 7-9 months for entire study, 1 day for control subjects ] [ Designated as safety issue: No ]

  The purpose of this research study is to determine the actual physical brain changes in people with cervical dystonia after Deep Brain Stimulator (DBS) surgery. We will do this by measuring your body's response to Transcranial Magnetic Stimulation (TMS) before and after DBS surgery, unless you are a control subject. If you are control subject, we will measure your body's response to TMS on one occasion for comparison purposes.

  For cervical dystonia patients, we plan to perform TMS one month before Deep Brain Stimulator (DBS) surgery, and again at 3- and 6-months after DBS surgery. These repeated tests should help us learn whether the electrical changes in the brain have any relation to the physical benefits patients with primary cervical dystonia receive from DBS surgery.

  
  

The first study visit will be performed one to four weeks before surgery (if you are not a control subject). If you are a control subject, this will be your only study visit. The following tests and /or evaluations will be obtained on this visit:

1. A neurological examination with special attention to the sensory system will be performed. The sensory system is the system by which the brain receives and perceives feelings from different body parts.
2. For non-control patients only: Scales used for clinical assessment of dystonia will be video recorded. These scales will be Toronto Western Cervical Dystonia Rating Scale (TWSTRS,) the SF-36 scale for quality of life assessment, Visual Analog Scale for assessment of dystonia and pain severity, MMSE instrument for cognitive testing and Beck Depression Inventory (BDI II), for evaluation of mood. We will not collect these scales on control subjects.
3. We will determine your individual Motor Evoked Potential (MEP) threshold before beginning the study treatment. MEP will be recorded from a muscle located between right thumb and index finger. MEP threshold refers to the amount of stimulation to the brain that is required to activate muscle cells enough to appear on an EMG (electromyography), which records electrical potential in muscle through electrodes placed on the skin.
4. We will test your sensory system and its interaction with the motor cortex by using Transcranial Magnetic Stimulation (TMS). For these tests, you will sit in a chair that looks like one you would find at the dentist's office. A nerve stimulator will be placed at the wrist of your right hand to stimulate the median nerve; the intensity of the nerve stimulator will be gradually increased until the right thumb begins to twitch. A magnetic coil will be placed on the scalp on one side of the head, overlying your brain's motor cortex (as shown in picture below) to stimulate your brain's output to the muscles in the opposite hand.

Study Visit 2 (for non-control patients only):

This study visit will be performed three months after DBS surgery on two consecutive days. Each day your DBS stimulator will be kept either ON or OFF. Separate days are chosen to allow time after each stimulator adjustment. You will be seen by the study doctor; a focused history will be obtained of how well you have been doing since your previous visit and since DBS surgery. A physical examination will be performed and the clinical scales and TMS tests used during Visit 1 will be applied and recorded on both days.

Study Visit 3 (for non-control patients only):

This study visit will be performed six months after DBS surgery on two consecutive days. The method and plan will be identical to that used during visit 2.