OBJECTIVES—To investigate the pathophysiology of selective absence of F waves and its relation with antiganglioside antibodies in Guillain-Barré syndrome (GBS). Some patients with GBS show the absence of F waves as an isolated conduction abnormality, which has been interpreted as demyelination in the proximal nerve segments. METHODS—In 62 consecutive patients with GBS, sequential nerve conduction and F wave studies were reviewed, and antibodies against ganglioside GM1, GM1b, GD1a, GalNAc-GD1a, GD1b, and GQ1b were measured by an enzyme linked immunosorbent assay. RESULTS—In the first electrophysiological studies, isolated absence of F waves was found in 12 (19%) patients. Sequential studies in 10 of these patients showed two electrophysiological sequel patterns; rapid restoration of F waves (six patients), and persistent absence of F waves with distal motor nerve degeneration (acute motor axonal neuropathy, four patients). None of the 10 patients showed evidence of demyelination in the proximal, intermediate, or distal nerve segments throughout the course. Of the 62 patients, IgG antibodies against GM1, GM1b, GalNAc-GD1a, or GD1b were significantly associated with the electrodiagnosis of acute motoraxonal neuropathy, and patients with these antibodies more often hadisolated absence of F waves than patients without them (11 of 36 (31%)v one of 26 (4%);p<0.01). Eleven of the 12 patients withisolated absence of F waves had positive serology for one or moreantiganglioside antibodies. CONCLUSIONS—In GBSwith antiganglioside antibodies, isolated absence of F waves is afrequent conduction abnormality especially in the early phase of thedisease, and may be caused by axonal dysfunction, such as physiologicalconduction block or axonal degeneration at the nerve roots.
