Movement-Related Brain Networks Involved in Hand Dystonia

Overview

This study will use various methods to measure the activity of the motor cortex (the part of the brain that controls movements) in order to learn more about focal hand dystonia. Patients with dystonia have muscle spasms that cause uncontrolled twisting and repetitive movement or abnormal postures. In focal dystonia, just one part of the body, such as the hand, neck or face, is involved. Patients with focal hand dystonia and healthy normal volunteers between 18 and 65 years of age may be eligible for this study. Each candidate is screened with a medical history, physical examination and questionnaire. Participants undergo the following procedures: Finger Movement Tasks Subjects perform two finger movement tasks. In the first part of the study, they move their index finger repetitively from side to side at 10-second intervals for a total of 200 movements in four blocks of 50 at a time. In the second part of the study, subjects touch their thumb to the other four fingers in sequence from 1, 2, 3 and 4, while a metronome beats 2 times per second to help time the movements. This sequence is repeated for a total of 200 movements in four blocks of 50 at a time. Electroencephalography This test records brain waves. Electrodes (metal discs) are placed on the scalp with an electrode cap, a paste or a glue-like substance. The spaces between the electrodes and the scalp are filled with a gel that conducts electrical activity. Brain waves are recorded while the subject performs a finger movement task, as described above. Magnetoencephalography MEG records magnetic field changes produced by brain activity. During the test, the subjects are seated in the MEG recording room and a cone containing magnetic field detectors is lowered onto their head. The recording may be made while the subject performs a finger task. Electromyography Electromyography (EMG) measures the electrical activity of muscles. This study uses surface EMG, in which small metal disks filled with a conductive gel are taped to the skin on the finger. Magnetic resonance imaging MRI uses a magnetic field and radio waves to produce images of body tissues and organs. The patient lies on a table that can slide in and out of the scanner (a narrow metal cylinder), wearing earplugs to muffle loud knocking and thumping sounds that occur during the scanning. Most scans last between 45 and 90 minutes. Subjects may be asked to lie still for up to 30 minutes at a time, and can communicate with the MRI staff at all times during the procedure. Questionnaire This questionnaire is designed to detect any sources of discomfort the subject may have experienced during the study.

Objective Dystonia is a disabling movement disorder that manifests with sustained co-contraction of agonist and antagonist muscles, giving rise to abnormal twisted postures and overflow of muscle activity. Abnormal neurophysiologic parameters of the somatosensory and motor cortex have been demonstrated, although it is unclear how these changes lead to the predominant motor manifestations. In normal voluntary movement, communication between sensory and motor cortices is important and these interactions may be dysfunctional in dystonia. Coherence is a powerful method used to assess brain communication and has been instrumental in demonstrating the interregional interactions involved in normal movement. Inappropriate connectivity in terms of the duration of communication or the extent of spread over sensorimotor areas may give rise to the involuntary overflow of movements that characterize dystonia. We propose to examine changes in coherence associated with disorganized movements to yield insight as to the brain networks involved in the development and expression of the disease. Study population Patients with focal hand dystonia and normal volunteers will take part in the study. Design In this study, EEG/MEG coherence analysis will be used to investigate corticocortical and corticomuscular interactions during voluntary hand movements in focal hand dystonia patients and normal subjects. Power spectral changes in the beta and alpha frequency range over the hand sensorimotor cortex will be studied using a 28-channel EEG montage while subjects perform various tasks involving the hand. The interregional coherence between sensory and motor, premotor and motor, and interhemispheric cortices will be assessed for changes between study populations. Outcome Measures Comparison of interregional coherence changes will be performed between dystonia patients and normal volunteers as well as between affected and unaffected sides. Furthermore, coherence changes will be compared between rest and during task performance.