The cortical silent period and amyotrophic lateral sclerosis.
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.
Prout
A J
AJ
Neuromuscular Diseases Unit, Vancouver General Hospital, University of British Columbia, Vancouver, Canada.
Eisen
A A
AA
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D004056:Differential Threshold; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D012016:Reference Values