The ubiquity of contraction enhanced H reflexes: normative data and use in the diagnosis of radiculopathies.

Surface recorded contraction enhanced H reflexes to single stimuli were obtained from muscles supplied by the C5, 6, 7, 8, L3, 4, 5, S1 and 2 nerve roots. For each of 12 such muscles, these reflexes were recorded from 25 control subjects as well as standard unenhanced H reflexes from the gastrocnemius muscles. Amplitude and latency criteria for normality were determined. Thirty-two patients with typical histories and physical findings of radiculopathy secondary to degenerative disease of the spine (C6 nerve root - 9 patients, C7 - 10, C8 - 4, L4 - 4, L5 - 4, S1 - 1) were studied with these H reflexes and the needle electrode. Thirty patients had H reflex abnormalities appropriate to the signs and symptoms. Eighteen had absent H reflexes and 16 had abnormalities to amplitude criteria. None were abnormal by latency criteria. Twelve patients had abnormal needle examinations and all also had abnormal H reflexes. These results indicate that contraction enhanced H reflexes are ubiquitous, readily obtainable and sensitive to the presence of clinically clear-cut radiculopathies.