[The spinal monosynaptic reflexes elicited from the tibialis anterior muscle--standardization of the reflexes and diagnostic use in L5 radiculopathy].

The spinal monosynaptic reflexes evoked in the tibialis anterior muscle were investigated to establish a practical method for assessing L5 radiculopathy. Voluntary contraction and averaging technique made it possible to consistently obtain the H-and T-reflexes from the muscle in which these reflexes are normally unelicitable at rest. Based on the study of fifty normal subjects, formulae were produced by an analysis of the simultaneous regression of the latencies of these reflexes on height and age, because these latencies were highly correlated with them. A side-to-side latency difference of the H-and T-waves greater than 1.5 msec. and 2.3 msec. respectively, and/or low amplitude less than 26% and 39% of the amplitude of the contralateral side respectively, could be considered abnormal. According to these criteria, eight out of twelve patients (67%) with unilateral compressive L5 radiculopathy showed abnormalities.