Comparison of three methods for recording tibial H reflex - A clinical note

Recording the tibial H reflex from the calf is routine in clinical electrom yography. Two widely used methods are Hugon's and Braddom and Johnson's. Bo th methods produce an H wave with an initial positive deflection. Another m ethod, the "half and half" method, generates an H wave with an initial nega tive deflection. To compare these methods, H-reflex responses were recorded in the right calf of 20 normal adults with each method using identical amp lifier and stimulator settings. Stimulus current was increased by increment s of 0.5-1.0 mA until the Fl reflex and motor (M) wave responses reached ma ximum amplitudes (Hmax, Mmax). H wave to M wave (H/M) amplitude ratios were calculated. The half-and-half method produced greatest Hmax, Mmax, and H/M ratio. Wave form configuration for the half-and-half method was biphasic w ith an initial negative deflection; it was triphasic with an initial positi ve deflection with the other methods. The shapes of M and H waves were simi lar in two methods but dissimilar in one. Because of the greater amplitude and the initial negative deflection, the Fl wave may be easier to detect wi th the half-and-half method and may present a latency that is more easily d etermined. For these reasons, the half-and-half method is recommended for m easuring amplitude and latency in clinical settings.