H-reflex in known as a useful electrodiagnostic test in the diagnosis of S1 radiculopathy. But, only the latency difference has been the useful parameter by previous method.

Under the assumption that the constant initial negative biphasic appearance of H-wave in essential so that the parameters such as amplitude, area and shape could be used as another significant parameters, we developed new H-reflex study method.

To validate our assumption and to compare the diagnostic value between the previous method and the new one, we studied H-reflex study in 330 subjects.

162 subjects were studied by previous method and 168 subjects were studied by our new method.

There was no definite differences in diagnostic values between two methods by latency criteria. But new method was more specific for S1 radiculopathy than previous method by amplitude and area criteria and the parameters such as amplitude, area and shape can be used as significant parameters only in the new method.

So, we suggest new diagnostic criteria as follows;

1) H-latency difference over 1.0 msec and H/H amplitude ratio less than 0.5 seems to be abnormal.

2) or, H-latency over 30 msec seems to be abnormal.

3) or, Unilateral no evoked H response seems to be abnormal