Electrophysiologic evidence of severe distal nerve segment pathology in the Guillain-Barré syndrome

We report the clinical and electrophysiologic findings in 4 patients with Guillain-Barré syndrome (GBS) who, within 48 hours of onset, progressed to flaccid quadriplegia. Evoked muscle action potentials were absent or prolonged in latency and markedly reduced in amplitude within 48 hours of onset of weakness at a time when sensory nerve studies were almost normal. We conclude that pathophysiologic abnormalities may be distal and severe in some patients with GBS and that there is a predilection for motor axons in GBS.