The Hoffman reflex has been used to study integration of the first sacral spinal segment and its afferent-efferent pathway. H-reflexes recorded from other level has not been used routinely because of technical difficulties and lack of normative data.

The objectives of this study were to standardize the parameters of FCR H-reflex and to investigate the clinical availability of FCR H-reflex study in the 6th or 7th cervical radiculopathies.

We recorded the H-reflex from flexor carpi radialis in 60 healthy subjects as control, and 40 patients who were considered to have the 6th or 7th cervical radiculopathies by needle electromyography. The normal subjects were divided into three groups by the length of their upper extremities. The 38 limbs were measured below 80cm(Group A), 46 limbs from 80 cm 89.9cm(Group B), and another 36 limbs above 90 cm(group C). And the latencies of FCR H-reflex were standardized by the length of their upper extremities. We compared the latencies of FCR H-reflexes and the findings from MRI.

The results were as follows;

1) The mean values of the parameters of FCR H-reflex in healthy subjects were 13.86±0.49msec in latency and 1.12±0.67mV in amplitude.

There was no significant difference of the latencies and amplitudes of FCR H-reflexes between sides and sexes.

2) The mean latencies of FCR H-reflex were 13.28±0.38 msec in group A, 13.98±0.28 msec in group B, and 14.08±0.60 msec in group C, and there was significant difference(P<0.001). A single regression equation was calculated for FCR H-reflex as a function of arm length; `Latency of FCR H-reflex=0.047×arm length(cm)+9.9'. This relationship was highly significant(P<0.001).

3) 34 patients(85%) showed abnormal latencies of FCR H-reflexes in group of patients.

4) 4 patients with normal findings from MRI showed normal latencies of FCR H-reflexes.

In conclusion, we present the reference value of the latency of FCR H-reflex and the measurement of the latency of flexor carpi radialis H-reflex in consideration of patient's arm length proved helpful to increase accuracy for diagnosing sixth or seventh cervical radiculopatheis.