Electrodiagnostic findings related to anti-GM1 and anti-GQ1b antibodies in Guillain-Barré syndrome.

Antibodies against the gangliosides GM1 and GQ1b may induce conduction failure in mice. To investigate their possible site of action in the Guillain-Barré syndrome (GBS), we studied the relation between serum anti-GM1 and anti-GQ1b antibodies and electromyography in 124 GBS patients. Anti-GM1 antibodies were found in 22 (18%) and anti-GQ1b antibodies in 5 (4%) patients. Anti-GM1 antibodies were associated with low distal compound muscle action potential amplitudes and relatively high compound sensory nerve action potential (CSNAP) amplitudes. In none of the patients with anti-GQ1b antibodies could CSNAPs be detected. Patients with anti-GM1 and anti-GQ1b antibodies were heterogenous with respect to electrodiagnostic features exclusive fordemyelination oraxonal degeneration, although the anti-GM1 positive patients tended to have more axonal degeneration. In conclusion, electromyographic studies indicate selective and more severe damage of motor nerves in patients with anti-GM1 antibodies, while patients with anti-GQ1b antibodies have more severe damage of sensory nerves. These antibodies may interfere with the electrophysiologic properties of different nerve fibers and thereby contribute to the clinical heterogeneity in GBS.