Electrophysiological studies in the Guillain-Barré syndrome.

Electrophysiological studies were performed on 114 patients with Guillain-Barré syndrome and the literature was reviewed. Abnormalities of motor and sensory conduction were present in about 90% of the patients. Because of the patchy distribution of demyelinating lesions, the likelihood of detecting electrophysiological abnormalities increases with the number of nerves studied. Marked slowing of conduction or an abnormally prolonged distal motor latency consistent with demyelination was found in one or more nerves in about 50% of the patients. Abnormalities of conduction not present in the early stages of the illness may become evident at the peak of disability or during the recovery phase. The application of F-wave studies and somatosensory evoked potential recordings may assist in detecting demyelination in roots and proximal segments of the peripheral nervous system. There is no correlation between the degree of slowing of conduction and the duration of illness or the long-term prognosis. Abnormalities of conduction at follow-up do not correlate with the clinical disability. On the other hand, electromyographic findings of abundant spontaneous fibrillation and other evidence of axonal degeneration are associated with a poor prognosis for complete recovery and also with a slower rate of recovery from the initial illness.