Pathophysiology of fasciculations in ALS as studied by electromyography of single motor units
Article first published online: 13 OCT 2004
Copyright © 1982 John Wiley & Sons, Inc.
Muscle & Nerve
Volume 5, Issue 3, pages 202–208, March 1982
How to Cite
Conradi, S., Grimby, L. and Lundemo, G. (1982), Pathophysiology of fasciculations in ALS as studied by electromyography of single motor units. Muscle Nerve, 5: 202–208. doi: 10.1002/mus.880050305
- Issue published online: 13 OCT 2004
- Article first published online: 13 OCT 2004
- Manuscript Accepted: 28 SEP 1981
- Manuscript Received: 4 JAN 1980
Electromyographic potentials of fasciculations were studied in ten patients with amyotrophic lateral sclerosis (ALS). The EMG recordings were made from the extensor digitorum brevis muscle. The EMG recording was so selective that only one motor unit potential appeared on maximal voluntary effort and on supramaximal electrical stimulation of the peroneal nerve. In a series of fasciculations, the shapes of the EMG potentials varied, while in a series of voluntary twitch activations of electrical nerve stimulations the EMG potentials were mainly constant. Fasciculations were followed by antidromic impulses in the test unit axon as judged from collision tests, and they persisted after lidocaine blockades of the nerve to the muscle. The findings are compatible with a conclusion of distal multifocal triggering of fasciculation. Fasciculating motor units had voluntary firing properties close to those of normal low-threshold motor units. Widespread fasciculations were abolished by a nonparalytic dose of a synthetic curare derivative (Pavulon) and augmented by administration of neostigmine in two cases. The fasciculations in ALS thus have the same characteristics as experimental fasciculations evoked by cholinesterase inhibitors, and there is reason to believe that the underlying pathophysiological mechanism is similar in the two cases.