title: Utility of multi-channel surface electromyography in assessment of focal hand dystonia.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Neurological Sciences, Christian Medical College, Vellore, India, 632004.
authors.forename: Ajith
authors.initials: A
authors.lastname: Sivadasan
authors.forename: M
authors.initials: M
authors.lastname: Sanjay
authors.forename: Mathew
authors.initials: M
authors.lastname: Alexander
authors.forename: Suresh R
authors.initials: SR
authors.lastname: Devasahayam
authors.forename: Babu K
authors.initials: BK
authors.lastname: Srinivasa
mesh_terms: D000328:Adult; D001676:Biofeedback, Psychology; D016022:Case-Control Studies; D004185:Disability Evaluation; D020821:Dystonic Disorders / Q000473:pathology* / Q000534:rehabilitation*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D019018:Imagery, Psychotherapy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D019370:Observation; D013997:Time Factors; D014956:Writing; D055815:Young Adult
keywords: delayed offset; early onset; focal hand dystonia (FHD); mirror activity; surface electromyogram (SEMG)