**Characteristics of the F-Wave and H-Reflex in Patients with Cerebrovascular Diseases: A New Method to Evaluate Neurological Findings and Effects of Continuous Stretching of the Affected Arm**

Toshiaki Suzuki, Tetsuji Fujiwara, Makiko Tani and Eiichi Saitoh

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/55887

**1. Introduction**

The F-wave is a result of the backfire of α-motoneurons following an antidromic inva‐ sion of propagated impulses across the axon hillock (Kimura, 1974). Its occurrence reflects excitability changes in the spinal motor neurons, as reported in patients with spasticity (Odusote & Eisen, 1979) and in healthy subjects with isometric contraction (Suzuki, Fujiwara & Takeda, 1993). In our previous study that investigated the nervous system of hemiplegic patients, excitability of spinal neural function was evaluated using F-wave data of patients with cerebrovascular disease (CVD) (Suzuki, Fujiwara & Takeda, 1993). We also reported that the persistence and amplitude ratio of F/M in patients with CVD were affected by the grade of muscle tonus, tendon reflex, or voluntary movement. Persistence reportedly depends on the number of neuromuscular units activated, while the ampli‐ tude ratio of F/M depends on their excitability (Eisen and Odusote, 1979). Therefore, we concluded that F-wave measurement was an effective neurological test for evaluating muscle tonus and voluntary movements.

Generally, current stimulus intensity required to generate an F-wave is 20% more than that required to generate a supramaximal M-wave because only the F-wave appears in healthy subjects; the H-reflex that is elicited by electrical stimulation of a peripheral mixed nerve, especially muscle spindle Ia fibers, does not appear in healthy subjects. However, we observed that the H-reflex could be evoked with supramaximal stimulation, a test for

measuring the F-wave in CVD patients with hypertonus and hyperreflexia. As a result, the H-reflex can be mistaken for an F-wave during F-wave measurement using supramaxi‐ mal stimulation.

We hypothesized that evaluation of F-wave and H-reflex patterns resulting from in‐ creased stimulus intensity in CVD patients could be a potential new method for the neurological evaluation of the affected arm or leg. In this report, we investigated the excitability of spinal neural function by evaluating H-reflex and F-wave patterns result‐ ing from increased stimulus intensity during muscle relaxation in healthy subjects and CVD patients. The results were analyzed in terms of the characteristic appearance of the Hreflex and F-wave in the healthy subjects and the relationship between the neurological findings of CVD and the characteristic appearance of the H-reflex and F-wave in the CVD patients.

In the field of rehabilitation medicine, muscle stretching is generally used to increase range of motion and improve muscle tonus. The effects of leg muscle stretching have been previously evaluated using H-reflex data (Angel et al., 1963 and Nielsen et al., 1993), and the results showed that the H-reflex following passive stretching was decreased to a lesser extent in spastic patients than in healthy subjects. However, in that study, the calf muscles and not the arm muscles were stretched; moreover, the periods of continuous stretching were differ‐ ent.Therefore, we also investigated the effects of continuous stretching of the affected arm for 1 min by evaluating H-reflex and F-wave characteristics in different stretched arm positions in the CVD patients.
