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May 1, 1996

Cortical projections to spinal motoneurons
Changes with aging and amyotrophic lateral sclerosis

May 1996 issue
46 (5) 1396

Abstract

Peristimulus time histograms (PSTHs) of discharging single motor units, recorded from the extensor digitorum communis (EDC) during randomly applied cortical magnetic stimulation, were obtained in 42 normal subjects aged 24 to 83 years and 42 patients with amyotrophic lateral sclerosis (ALS) aged 37 to 84 years. Normal subjects had an early period of increased firing probability occurring at about 20 msec poststimulus, reflecting an underlying compound excitatory postsynaptic potential (EPSP) induced by fast-conducting, descending volleys of the corticomotoneuronal core facilitating the single spinal motoneuron. There was an age-dependent, linear decline in the amplitude of the EPSP (r = 0.673). We estimated that by age 50 years about 35% of corticomotoneurons are lost or nonfunctioning in normal controls. Compared with age-matched controls, the EPSP in most patients with ALS was reduced, and it was unmeasurable in six. We postulate this reflects a loss of corticomotoneurons. Seven (16.7%) patients phenotypically the same as the others had EPSPs that were larger than age-predicted values. This may reflect glutamate-induced excitotoxicity in a subset of ALS. In a single patient with chronic spinal muscular atrophy the EPSP was normal.

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Information & Authors

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Published In

Neurology®
Volume 46Number 5May 1996
Pages: 1396
PubMed: 8628489

Publication History

Published online: May 1, 1996
Published in print: May 1996

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Authors

Affiliations & Disclosures

Andrew Eisen, MD, FRCP(C)
Neuromuscular Diseases Unit, Vancouver General Hospital, and the University of British Columbia, Vancouver, BC, Canada.
Mohammed Entezari-Taher, MD
Neuromuscular Diseases Unit, Vancouver General Hospital, and the University of British Columbia, Vancouver, BC, Canada.
Heather Stewart, BSc, RT(EMG)
Neuromuscular Diseases Unit, Vancouver General Hospital, and the University of British Columbia, Vancouver, BC, Canada.

Notes

Address correspondence and reprint requests to Dr. Andrew Eisen, The Neuromuscular Diseases Unit (EMG), Vancouver General Hospital, 855 12th Avenue West, Vancouver, BC, V5Z 1M9, Canada.

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