Electrophysiological studies of Guillain-Barré syndrome with different susceptibilities to develop EAN serum on 2 strains of rats.

Sera from 10 patients with AIDP and 10 age-matched controls were microinjected into the tibial division of rat sciatic nerve using improved microinjection techniques and coded sera. No statistically significant changes in conduction velocity or amplitude of the compound muscle action potential (CMAP) or in the monophasic compound action potential (CAP) parameters was found at 1 week. In nerves studied with serial recording over 1 h a small but significantly greater reduction in CMAP amplitude was observed at 60 min in the AIDP group and at both 30 and 60 min when only sera from very severely affected (bed-ridden) patients were considered. A similar reduction was found following microinjection into focally demyelinated nerves. The finding of a small reduction in CMAP amplitude in the first hour suggests the presence in some AIDP patients of serum blocking or demyelinating factors but the clinical significance of this small reduction is uncertain.