Transcranial Electrical Polarization to Treat Focal Hand Dystonia

Overview

This study will evaluate the effect of transcranial electrical polarization (TEP), also called direct current (DC) stimulation, on focal hand dystonia in people with writer's cramp. In dystonia, muscle spasms cause uncontrolled twisting and repetitive movement or abnormal postures. Focal dystonia involves just one part of the body, such as the hand, neck or face. When people with focal hand dystonia make small and repeated movements with their hands, there is extra activity in the part of the brain called the motor cortex. TEP is a method of brain stimulation that slows down the activity of the nerve cells in the motor cortex. This study may help researchers develop new ways to treat focal hand dystonia. People 18 years of age and older with focal hand dystonia may be eligible for this study. Participants have a neurological examination and are randomly assigned to one of two treatment groups: TEP or placebo stimulation. The TEP group receives stimulation to the parts of the brain used for hand movement, and the placebo group receives sham stimulation, which does not affect any area of the brain. There are three TEP/placebo sessions over a period of 7 to 10 days. The first session may last up to 2-1/2 hours; the other two sessions last 1-2 hours. For TEP, sponge electrodes are placed on the scalp and an electrical current is passed through the scalp and skull to the outer part of brain. Before and after each session, participants have a neurological examination, including an evaluation of the rate and severity of their movement problems. For this assessment, participants do a writing test while the electrical activity of their hand muscles is recorded using surface electromyography (EMG). For EMG, small metal disks (electrodes) filled with a conductive gel are taped to the skin over the muscles being tested. Patients are followed in the clinic the day after the end of TEP treatment for evaluation of their movement abilities and the effects of therapy, such as improvement of handwriting.

Objective: The treatment of focal hand dystonia (FHD) needs further improvement. A deficiency of inhibition was demonstrated in patients with writer's cramp. The passage of weak DC currents across the head, or transcranial electrical polarization (TEP) has been done for many years with numerous effects described in healthy subjects and mentally diseased patients. Recently, it has been shown by objective means, in controlled experiments, that this type of treatment has robust and lasting effects on the excitability of the motor cortex in healthy humans. Study population: 40 subjects with focal hand dystonia. Design: We hypothesize that TEP will have a beneficial effect on hand writing in patients with FHD because it will decrease the excitability of the motor cortex compensating the deficiency of inhibition. Specifically, we propose to look at the effect of 2 mA TEP with cathode position over the hand projection in the contralateral to the affected hand primary motor cortex. Anodes will be placed over the orbit and mastoid process ipsilateral to the affected hand (contralateral to the cathode). Over a two-year period, we will enroll 40 patients with FHD and evaluate the acute TEP effects over a period of 1 week (3 TEP sessions). Outcome measures: Symptoms will be evaluated by kinematic analysis of the handwriting and with dystonia scales.