Effects of transcutaneous electrical nerve stimulation on H-reflex and spinal spasticity

Abstract

The purpose of this study was to investigate the short-term effects of transcutaneous electrical nerve stimulation (TENS; 99 Hz; 250 ms pulses) on H-reflex and spinal spasticity. Considering the reflex hyperexcitability commonly displayed in spinal cord-injured subjects, it was hypothesized that repetitive low threshold afferent stimulation would have an inhibitory effect on the triceps surae H-reflexes which could also be reflected by a decrease in plantarflexor spasticity. Clonus, Achilles tendon reflex and modified Ashworth evaluations were performed on 14 spinal cord-injured subjects prior to and after 30 minutes' application of TENS. Non-parametric statistical analyses (n = 14; alpha = 0.05) failed to reveal significant effects of TENS on H-reflex amplitude. However, there was a significant decrease in scores for the Achilles tendon reflex and the modified Ashworth test. The clonus score decreased in most subjects post-TENS, although not in a statistically significant manner. The present pilot results thus suggest that TENS appears to be effective in reducing spinal spasticity, as measured clinically.