[Sequential studies of motor nerve conduction in relation to the disease stages of Guillain-Barré syndrome].
We retrospectively studied sequential changes in motor nerve conduction in forearm segments of 17 median nerves in 9 consecutive patients with Guillain-Barré syndrome (GBS). The disease course was divided into 6 stages: progressing, nadir, early-, mid- and late-convalescent, and cured stages. All patients were tested on at least 3 occasions in each different stage. Low amplitude compound muscle action potentials (CMAP) were noted in the progressing and nadir stages, suggesting the presence of conduction block. In the early- and mid-convalescent stages, on the other hand, the delays in distal motor latencies and conduction velocities as well as temporal dispersions of CMAPs were more prominent than in the progressing or nadir stage. These findings suggest that pathophysiological processes are different in the two stages of GBS: demyelination with conduction block predominated in the earlier stage and demyelination without conduction block predominated in the later stage. The former is considered to involve predominantly the relatively smaller motor nerves during the progressing and nadir stages, producing muscle weakness but not causing marked slowing of the motor nerve conduction. The latter is considered to involve predominantly the fastest motor fibers in the later days lasting into the early- and even mid-convalescent stages. This process seems to produce marked conduction slowing, but does not cause prominent muscle weakness. In addition, recovery from the conduction block during the convalescent stages produces temporal dispersions of CMAPs because of the variably slowed conduction velocities.(ABSTRACT TRUNCATED AT 250 WORDS)