Axonal involvement at the common entrapment sites in Guillain-Barré syndrome with IgG anti-GM1 antibody.

If anti-GM1 antibody plays a role in the axonal damage in Guillain-Barré syndrome, the common entrapment sites may be preferentially involved with evidence of axonal dysfunction. To assess this hypothesis, we studied nerve conduction across the cubital tunnel in 44 patients. Abnormal amplitude reduction of compound muscle action potentials (CMAPs) was found in 45% of 20 immunoglobulin G (IgG) anti-GM1-positive and in 29% of 24 anti-GM1-negative patients. The time course and sequel were distinct between the two groups. In the former group, the amplitude reduction was prominent in weeks 1 to 2 and was followed by a decrease in distal CMAPs (axonal degeneration) or an increase in proximal CMAPs (resolution of conduction block). In contrast, anti-GM1-negative patients showed slower resolution with temporal dispersion. In anti-GM1-positive cases, amplitude reduction at the common entrapment site is frequent and may reflect wallerian degeneration or physiological conduction block at the nodes of Ranvier, both suggesting axonal involvement. Copyright 1999 John Wiley & Sons, Inc.