title: Abnormal spinal interactions from hand afferents to forearm muscles in writer's cramp.
abstract: OBJECTIVE
  Spinal reflexes from hand to wrist muscles were investigated in writer's cramp.
  
  
  METHODS
  Stimulus-triggered rectified EMG averages after ulnar nerve and cutaneous stimulation, in wrist flexors and extensors during tonic contraction, were compared in 18 controls and 19 patients.
  
  
  RESULTS
  On the patient dystonic side, ulnar-induced EMG suppression was decreased in wrist extensors, and facilitation in wrist flexors modified dependent on the dystonic wrist posture during writing. No change was found on the patient non-dystonic side. Cutaneous stimulation increased wrist flexor EMG on both sides of the patients with normal wrist posture during writing, but had no effect in controls and patients with abnormal wrist posture.
  
  
  CONCLUSIONS
  Comparison between cutaneous and mixed nerve stimuli suggests that spindle afferents from intrinsic hand muscles may mediate patients' ulnar-induced EMG modulations. Abnormal proprioceptive control was only observed on dystonic side, while bilateral unusual cutaneous control was found in patients. Changes in spinal transmission were partly related to the dystonic wrist posture, suggesting that systems involved in sensory processing can be differentially altered in writer's cramp.
  
  
  CONCLUSIONS
  Changes in spinal transmission, probably related to peripheral and/or cortical inputs, might either take part in primary or adaptive mechanisms underlying writer's cramp.
authors.affiliation: INSERM, U731, Paris F-75013, France.
authors.forename: G
authors.initials: G
authors.lastname: Lourenço
authors.forename: J-P
authors.initials: JP
authors.lastname: Bleton
authors.forename: C
authors.initials: C
authors.lastname: Iglesias
authors.forename: M
authors.initials: M
authors.lastname: Vidailhet
authors.forename: V
authors.initials: V
authors.lastname: Marchand-Pauvert
mesh_terms: D000328:Adult; D000368:Aged; D004185:Disability Evaluation; D020821:Dystonic Disorders / Q000503:physiopathology*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005542:Forearm / Q000294:innervation* / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000294:innervation* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology*; D009475:Neurons, Afferent / Q000502:physiology*; D011187:Posture / Q000502:physiology; D012867:Skin / Q000294:innervation; D013116:Spinal Cord / Q000503:physiopathology*; D014459:Ulnar Nerve / Q000502:physiology; D014953:Wrist / Q000294:innervation / Q000502:physiology