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

If anti-GM1 antibody plays a role in the axonal damage in Guillain-Barre sy ndrome, the common entrapment sites may be preferentially involved with evi dence of axonal dysfunction. To assess this hypothesis, we studied nerve co nduction across the cubital tunnel in 44 patients. Abnormal amplitude reduc tion of compound muscle action potentials (CMAPs) was found in 45% of 20 im munoglobulin G (IgG) anti-GM1-positive and in 29% of 24 anti-GM1-negative p atients. The time course and sequel were distinct between the two groups. I n the former group, the amplitude reduction was prominent in weeks 1 to 2 a nd was followed by a decrease in distal CMAPs (axonal degeneration) or an i ncrease in proximal CMAPs (resolution of conduction block), In contrast, an ti-GM1-negative patients showed slower resolution with temporal dispersion. In anti-GM1-positive cases, amplitude reduction at the common entrapment s ite is frequent and may reflect wallerian degeneration or physiological con duction block at the nodes of Ranvier, both suggesting axonal involvement. (C) 1999 John Wiley & Sons, Inc.