Multiple a waves in Guillain-Barre syndrome

In 13 of 14 patients with Guillain-Barre syndrome (GBS), we observed multip le A waves in at least one limb nerve on routine electroneurographic studie s within 7 days after onset of symptoms. The patient without A waves had a severe axonal type of GBS with tetraplegia and almost complete loss of M re sponses following electrical stimulation of limb nerves. In the remaining 1 3 patients, on average 8 +/- 2 (mean +/- SD) A waves were present in each t ibial nerve (n = 24) and 4 +/- 1 A waves in each peroneal nerve (n = 26). A bout half of the A waves were below 50 mu V in amplitude, whereas amplitude s were higher than 120 mu V in only 22 of 299 A waves. Of these A waves, 68 were not constantly elicitable. There was a significant correlation betwee n the number of A waves up to 50 ms poststimulus and the reduction in ampli tude of the compound muscle action potential when elicited with proximal co mpared to distal stimulation in the peroneal (n = 26, P < 0.0005; Kendall's tau) and tibial nerves (n = 24, P < 0.002). Therefore, in GBS both conduct ion block and A waves are presumably signs of inflammatory nerve lesions. T he existence of multiple A waves soon after onset of symptoms seems to be a sensitive sign of GBS. (C) 1999 John Wiley & Sons, Inc.