Conduction velocity in the proximal segments of a motor nerve in the Guillain-Barré syndrome.

Conduction velocity from spinal cord to axilla (estimated using the F wave) has been compared with conduction velocity from axilla to wrist (measured in the conventional manner) in the motor fibres of the ulnar nerve in 17 controls subjects and in 11 patients with the Guillain-Barré syndrome (GBS). In the patients with GBS the conduction velocity was, in general reduced to a similar extent in both the proximal and the distal portions of the motor fibres, suggesting that the disease process is usually diffuse. In two patients, however, the conduction velocity in the proximal segment was disproportionally reduced and in one of these the conduction velocity in the distal segment was normal. It is concluded that the estimation of conduction velocity in the proximal segments of motor nerves may be of value in the assessment of patients with GBS.