A Study on F Wave in Amyotrophic Lateral Sclerosis

ABSTRACT

F waves are motor responses produced by antidromic activation of motoneurons following stimulation of motor axons peripherally. The F wave is useful in evaluating proximal motor nerve conduction, in assessing the integrity of the ventral root, and in measuring the motor neuron excitability. This study was undertaken to assess the integrity of the lower motor neurons in amyotrophic lateral sclerosis(ALS). F-wave latency(FWL), F-wave conduction velocity(FWCV), F ratio, F-response frequency, and distal MNCV were determined in the median and tibial nerves of 9 patients with ALS. The results were compared with 32 healthy adult volunteers as controls. In patients with ALS, in contrast,to the control subjects, the mean FWL was prolonged, the mean FWCV and distal MNCV slowed, and the mean F-response frequency reduced. These results are thought to reflect some degree of loss of the lower motor neurons.