A study on new diagnostic criteria of H reflex.

H reflex is known as a useful electrodiagnostic test in the diagnosis of S1 radiculopathy. But, only the latency difference has been the useful parameter by previously published conventional method. Under the assumption that the constant appearance of initial negative biphasic H wave is critical to study H reflex using parameters such as amplitude, area and shape, we developed a new method using parameters such as amplitude, area and shape. To validate our assumption and to compare the diagnostic values between the conventional method and the new one, we studies H reflex in 330 subjects. One hundred sixty-two subjects were studied by conventional method and 168 subjects were studied by our new method. There was no definite difference in diagnostic values between two methods by latency criteria. However, new method was more specific for S1 radiculopathy than conventional method by amplitude and area criteria. Parameters such as amplitude, area and shape can be used significantly only in the new method. Therefore, we suggest new diagnostic criteria of abnormal response as follows: (1) H latency difference over 1.0 msec and H/H amplitude ratio less than 0.5 or (2) H latency over 30 msec or (3) unilateral absent evoked H response.