title: Double cortical stimulation in amyotrophic lateral sclerosis.
abstract: OBJECTIVE
  Transcranial double magnetic stimulation on the motor cortex was used to investigate central motor tract function in 16 patients with amyotrophic lateral sclerosis, five with spinal muscular atrophy, and 16 age matched normal controls.
  
  
  METHODS
  Surface EMG responses were recorded from the relaxed abductor pollicis brevis (APB) muscle.
  
  
  RESULTS
  Responses to test stimuli were markedly attenuated by a subthreshold conditioning stimulus given at a condition-test (C-T) interval of 1-4 ms in normal controls and patients with spinal muscular atrophy, but attenuation was mild in patients with amyotrophic lateral sclerosis. In the normal controls this suppression was caused by activation of the intracortical inhibitory mechanism because responses to electrical test stimuli and the H wave were not suppressed by the same magnetic subthreshold conditioning stimulus. In amyotrophic lateral sclerosis the effect of the conditioning cortical stimulus on the H wave was also in the normal range.
  
  
  CONCLUSIONS
  The intracortical inhibitory mechanism may be impaired in patients with amyotrophic lateral sclerosis.
authors.affiliation: Department of Neurology, Tokyo Medical and Dental University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yokota
authors.forename: A
authors.initials: A
authors.lastname: Yoshino
authors.forename: A
authors.initials: A
authors.lastname: Inaba
authors.forename: Y
authors.initials: Y
authors.lastname: Saito
mesh_terms: D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*