Conduction block and denervation in Guillain-Barré polyneuropathy.

The two main electrophysiological abnormalities seen in the first two weeks of the acute Guillain-Barré syndrome (GBS) were conduction block and, in some patients, low maximum M response amplitudes. In this study period, maximum motor and sensory conduction velocities were often in the normal range and temporal dispersion was relatively less common. The conduction block was generalized in its distribution in some peripheral nerves, while in others the block was predominantly proximal or distal in location. Conduction abnormalities in excess of those proximal or distal to it were frequent at common sites of entrapment. Very low M response amplitudes early in the course of the disease correlated well with the subsequent development and frequency of denervation in the muscle(s) and unfavourable clinical recovery. We conclude that conduction block is the main cause of the acute paralysis and sensory loss in the GBS. Axonal degeneration contributes variably to the acute disorder, but is the main cause of lasting disability.