Electrophysiological measurement at Erb's point during the early stage of Guillain-Barré syndrome.

This study aimed to find the electrophysiological significance of proximal nerve stimulation at Erb's point during the early stage of Guillain-Barré syndrome (GBS). Twenty-one healthy volunteers and 13 patients within the first week of GBS were studied. Latency and amplitude at wrist, elbow and Erb's point, and F waves were calculated after compound muscle action potentials (CMAP) were obtained at the median and ulnar nerve. There were statistically significant differences between groups for CMAP latency and amplitude at Erb's point for the median (p=0.005 and 0.001, respectively) and ulnar nerves (p=0.007 and 0.007, respectively). Latency or amplitude of CMAP after Erb's point stimulation was abnormal in 77% of patients while F wave latency was abnormal in only 46% of patients. Conduction block was observed in 62% of patients. Abnormal parameters at Erb's point were the only abnormality in four patients at the first electrophysiological examination. We conclude that electrophysiological examination at Erb's point is a simple and non-invasive method that can be used in the early stage of GBS, especially for patients who exhibit normal F waves and nerve conduction studies at distal nerves.