F-wave velocity in motor neurone disease

The F-wave velocity in the central segment (axilla to spinal cord) was studied employing the "collison technique" described by Kimura (1974), and compared with the conduction velocity obtained with the usual methods. In 25 normal subjects the F-wave velocity increased proceeding proximally, reaching the maximum values in the central tract (64.86 +/- 2.23 m/sec in ulnar nerve). In 11 patients affected by motor neurone disease and 11 patients affected by amyotrophic lateral sclerosis the F-wave velocity decreased significantly proceeding proximally and the minimum values were found in the central tract (52.51 +/- 2.15 m/sec in MND and 48.64 +/- 5.60 m/sec in ALS). We therefore suggest the use of F-wave velocity as a more complete element for precise localization of the lesion in the central segment when the motoneurone is primarily involved.