Serial action potential analysis in Guillain-Barré syndrome

Action potential analyses were carried out in 62 skeletal muscles of 16 patients with the Guillain-Barré syndrome. The muscles of a good prognosis showed only a slight change in duration, amplitude and phase of action potentials on electromyograms. On the other hand, the muscles of a poor prognosis showed a marked increase in duration and amplitude of action potentials, especially in the chronic stage. The incidence of polyphasic potentials was more frequent in the early stage than in the chronic stage of the muscles of a poor prognosis. The changes in duration in the early stage of a poor prognosis muscles were similar to those of acute beriberi neuropathy and the changes in the later stage were similar to those of amyotrophic lateral sclerosis, both of which showed axonal degenerations. In the early stage, myopathy-like changes in electromyography were often noticed, but the muscle biopsy showed only early neurogenic changes. Coupling or satellite discharges were found most frequently six or eight months after the onset, and decreased in number in the chronic stage. Satellites with blockings appeared earlier than those without blockings. A poor prognosis might be induced by an axonal degeneration partly together with segmental demyelinations.