Utility of multi-channel surface electromyography in assessment of focal hand dystonia.
INTRODUCTION
Surface electromyography (SEMG) allows objective assessment and guides selection of appropriate treatment in focal hand dystonia (FHD).


METHODS
Sixteen-channel SEMG obtained during different phases of a writing task was used to study timing, activation patterns, and spread of muscle contractions in FHD compared with normal controls. Customized software was developed to acquire and analyze EMG signals.


RESULTS
SEMG of FHD subjects (20) showed "early onset" during motor imagery, rapid proximal muscle recruitment, agonist-antagonist co-contraction involving proximal muscle groups, "delayed offset" after stopping writing, higher rectified mean amplitudes, and mirror activity in contralateral limb compared with controls (16). Muscle activation latencies were heterogenous in FHD.


CONCLUSIONS
Anticipation, delayed relaxation, and mirror EMG activation were noted in FHD. A clear pattern of muscle activation cannot be ascertained. Multi-channel SEMG can aid in objective assessment of temporal-spatial distribution of activity and can refine targeted therapies like chemodenervation and biofeedback.
['Sivadasan|Ajith|A|', 'Sanjay|M|M|', 'Alexander|Mathew|M|', 'Devasahayam|Suresh R|SR|', 'Srinivasa|Babu K|BK|']
D000328:Adult D001676:Biofeedback, Psychology D016022:Case-Control Studies D004185:Disability Evaluation D020821:Dystonic Disorders D004558:Electric Stimulation D004576:Electromyography D005260:Female D007839:Functional Laterality D006225:Hand D006801:Humans D019018:Imagery, Psychotherapy D008297:Male D008875:Middle Aged D009119:Muscle Contraction D018482:Muscle, Skeletal D019370:Observation D013997:Time Factors D014956:Writing D055815:Young Adult
focal hand dystonia (FHD) early onset delayed offset mirror activity surface electromyogram (SEMG)