Effects of transcutaneous electrical nerve stimulation (TENS) on spasticity in patients with hemiplegia

The effect of afferent cutaneous electrical stimulation on the spasticity of leg muscles was studied in 20 patients with chronic hemiplegia after stroke. Stimulation electrodes were placed over the sural nerve of the affected limb. The standard method of cutaneous stimulation, TENS with impulse frequency of 100 Hz, was applied. The tonus of the leg muscles was measured by means of an electrohydraulic measuring brace. The EMG stretch reflex activity of the tibialis anterior and triceps surae muscles was detected by surface electrodes and recorded simultaneously with the measured biomechanical parameters. In 18 out of 20 patients, a mild but statistically significant decrease in resistive torques at all frequencies of passive ankle movements was recorded following 20 min of TENS application. The decrease in resistive torque was often (but not always) accompanied by a decrease in reflex EMG activity. This effect of TENS persisted up to 45 min after the end of TENS. The results of the study support the hypothesis that TENS applied to the sural nerve may induce short-term post-stimulation inhibitory effects on the abnormally enhanced stretch reflex activity in spasticity of cerebral origin.