F-wave in experimental allergic neuritis

The conduction velocity of volleys in motor fibres causing F waves, in addition to distal latency and to maximal motor conduction velocity of volleys in fibres causing the M response, were measured in the hindlimbs of control guinea pigs and rabbits and in those with experimental allergic neuritis (EAN). The spinal roots and sciatic nerves were examined histologically in the animals with EAN. The conduction time to the F wave was abnormal in the presence of normal maximal conduction velocity in fibres causing the M waves in 14% of the guinea pigs and 7% of the rabbits. However, conduction time to the F wave was prolonged in the presence of normal maximal motor conduction velocity in one case where no pathological abnormalities were found in the ventral roots and in some instances, F wave conduction time was within the normal range when ventral root and peripheral nerve demyelination was present. These findings highlight some of the problems in interpretation of F wave studies in man.