The cortical silent period and amyotrophic lateral sclerosis

Muscle Nerve. 1994 Feb;17(2):217-23. doi: 10.1002/mus.880170213.


The cortical silent period (C-SP) was elicited by transcranial magnetic stimulation in 25 normal subjects and 19 patients with amyotrophic lateral sclerosis (ALS). The inhibitory (S-X) period was highly stimulus intensity (SI)-dependent (mean r2 = 0.89 for both normals and patients with ALS). The range of the C-SP (difference between maximum and minimum S-X intervals) was age-dependent for normals (r2 = 0.701, P < 0.001) but not patients with ALS. Means, maximums and ranges for the C-SP were not significantly different between normal and ALS groups and thresholds to cortical stimulation were also comparable. There was a significant, linear, relation between the maximum C-SP and disease duration of ALS (P = 0.002). The maximum C-SP was shorter early in the disease. It is hypothesized that the reduced inhibition early in the course of ALS might reflect glutamate-induced corticomotoneuronal excitotoxicity.

MeSH terms

  • Adult
  • Aged
  • Aging / physiology
  • Amyotrophic Lateral Sclerosis / physiopathology*
  • Cerebral Cortex / physiopathology*
  • Differential Threshold
  • Electric Stimulation
  • Electromyography
  • Female
  • Humans
  • Magnetics
  • Male
  • Middle Aged
  • Reaction Time
  • Reference Values