In the diagnosis of radicular damage within the framework of lumboischialgic syndrome in addition to clinical examination two large groups of auxiliary examinations are used - imaging methods and electrophysiological methods. The H reflex is monosynaptic segmental reflex used in the electrophysi- ological diagnosis of radiculopathies of root S1. In more recent studies using an atypical pattern of the position of the recording and reference electrode in addition to the latency parameter of the H reflex also the amplitude parameter has become of interest. During 1997 - 1998 the authors examined 19 patients with clinically and CT confirmed vertebrogenically conditioned unilateral monoradiculopathy of S1, and 20 controls without signs of damage of the spinal roots. In all they assessed bilaterally the latency, amplitude, the difference in latencies of the two sides and the ratio of H amplitudes of the reflex. They found statistically significant differences, i.e. a significantly greater difference of the latencies of the two sides to the disadvantage of the affected side (p < 0.01) and a significantly greater difference when comparing the amplitude quotient, again to the disadvantage of the affected side (p < 0.02). On comparison of the mean values of absolute parameters - latencies and amplitudes of the H reflex - they did not find statistically significant differences between the group of patients and controls. In the control group they found pathological values only in one case (5 %), conversely the highest detection rate of pathological findings in the group of patients was held by the parameter of the amplitude quotient of the two sides (91 - 100 %). The results of the study indicate that when using the examination method based on experimental knowledge on the distribution of potential fields of the H reflex in the area of the leg valuable information can be obtained also when evaluating the amplitude parameter in particular when evaluating the different latencies and amplitudes of the H reflex on the two sides. The results correlate closest with the presence of pathological damage present concurrently in the sensory and motor part of the roots of S1. Examinations of the H reflex prove useful for the objective expression of damaged functions of nerve structures in the radicular distribution of S1.

        Key words: H reflex, root S1, lumboischialgic syndrome