Method
The subjects were 37 patients and 30 normal controls. The patient group was composed of 28 patients with L5 radiculopathy and 9 patients with S1 radiculopathy, which were confirmed by clinical, radiological, and electrodiagnostic studies. Tibialis anterior H-reflex (TA-H reflex) was recorded from maximally contracting tibialis anterior muscle by averaging technique and submaximal stimulation of common peroneal nerve. Sensitivities and specificities were delineated from the several diagnostic criteria.

Results
In the normal controls, mean side to side difference in the TA-H reflex latency was 0.66⁑0.48 msec and mean amplitude ratio was 75⁑16%. The diagnostic criteria of abnormal TA-H reflex were latency difference above 1.62 msec and amplitude ratio less than 42.2%. The abnormal TA-H reflexes were shown in 17 out of 28 patients with L5 radiculopathy and 1 out of 9 patients with S1 radiculopathy. Sensitivity and specificity of TA-H reflex as a diagnostic criteria of L5 radiculopathy were 61% and 89%, respectively.

Conclusion
Tibialis anterior H-reflex might be useful in the diagnosis of L5 radiculopathy.