The Importance of F-Wave Patterns in a Patient with Cerebrovascular Disease Characterized by a Markedly Increased Tone of the Thenar Muscles

Abstract

F-waves are used to measure the excitability of spinal motor nerve function. This study aimed to investigate the F-wave patterns in a patient with cerebrovascular disease who had no voluntary movement of the hand, particularly the thumb, caused by a considerably increased tone of the thenar muscles. A patient with right hemiplegia caused by left cerebral hemorrhage (putamen) showed a considerably increased tone of the thumb flexors and no voluntary movements. F-waves were recorded from the affected thenar muscles with median nerve stimulation in the supine lying position during the first trial. Exercise therapy that included stretching of the affected thenar muscles was performed twice a week for 20 min for 8 months. Subsequent changes in the F-wave waveform were examined and considered as second trial. The latency and persistence of the F-wave and F-wave conduction velocity did not show any significant change between the two trials. Compared with the first trial, the F/M amplitude ratio in the second trial was increased. Following 8 months of exercise therapy, muscle tone improved slightly, and minimal voluntary movements of the affected thumb were noted. Since motor function of the affected thumb improved with exercise therapy but there was no improvement in F-wave data, it was determined that the main factor underlying the hypertonicity of the thenar muscles in this patient was more likely due to secondary muscle shortening than to spasticity. Unclear waves that possibly were F-waves were also observed approximately 20 ms after the appearance of the M-wave in the first trial but not in the second trial. Because exercise therapy showed muscle tone improvement and did not result in the appearance of unclear waves, F-wave patterns should be monitored for evaluating spasticity, which markedly increases muscle tone in patients with cerebrovascular disease.