Influence of timing on electrodiagnosis of Guillain-Barré syndrome in the first six weeks: a retrospective study.

The effect of timing is uncertain on the electrophysiology of Guillain-Barré syndrome (GBS). On this may however depend the usefulness of systematic serial studies performed at specific time intervals. We retrospectively analyzed records of 118 consecutive patients with GBS from Birmingham, U.K. (2001-2012), studied between 0-14days, or, 15-42days post-onset using new criteria which we recently proposed [4]. Rates of acute inflammatory demyelinating polyneuropathy (AIDP) (p=0.45), axonal GBS (p=0.32) and equivocal forms (p=0.46) were similar for both timings. Similarly, no significant differences between timings were observed using Hadden et al.'s criteria. Proportions were comparable to published serial studies for both timings, for AIDP (p=0.25; p=0.10) and axonal GBS (p=0.73; p=0.56) but were higher than with serial studies for equivocal forms in patients studied on days 0-14 (p=0.012), although not in those studied on days 15-42 (p=0.17). This suggests that over the initial 6weeks post-onset, timing fails to influence subtype proportions in a large GBS cohort, irrespective of criteria used. Repeat studies appear therefore unlikely to be helpful when systematically performed within this time frame, except in equivocal cases. The benefit of repeat studies remains possible at other times but may need to be individualized, and requires future prospective evaluation.