Indirect discharges as an early nerve conduction abnormality in the Guillain-Barré syndrome

Abnormal electrophysiological findings may be delayed in the Guillain-Barré syndrome (GBS). In this study, conducted in 29 GBS patients, 23 patients (group 1) fulfilled the electrodiagnostic criteria for GBS [1]at the time of initial investigation, performed on average 22.3 days after onset of symptoms; whereas the 6 patients (group 2) who did not fulfil the criteria were first seen earlier, on average after 9.7 days. During the initial nerve conduction studies, numerous late responses, distinct from F waves, were observed in 26 of the 29 patients (90%), that is in 20 patients of group 1, and in all patients of group 2. Most of these responses, if not all, were indirect discharges (iDs) caused by proximal re-excitation on motor axons. If the iDs had been included in the electrodiagnostic criteria of GBS, all the patients of this series would have been diagnosed at the initial electrophysiological examination. We conclude that iDs occur frequently in GBS and are observed early in the disease. We recommend adding the presence of multiple iDs to the classical electrodiagnostic criteria of GBS.