H-reflex study of flexor carpi radialis muscle in healthy subjects

Parameters of the flexor carpi radialis H-reflex were studied with an aim to establish the reference values of our laboratory. The files of the individuals with normal electrophysiological studies were reviewed to determine the H-reflex latency, conduction velocity, maximum amplitude, right-left H-reflex latency difference, H-M interlatency, Hmax/Mmax ratio, right-left maximum amplitude ratio and their relation with the physiological factors.Although we were unable to obtain the H-reflex during rest in the majority of the individuals (63.7%), the reflex was present in almost all subjects during the facilitation maneuver (95%). The maximum amplitude, Hmax/Mmax ratio, right-left amplitude ratio of the H-reflex were significantly increased during the facilitation maneuver compared to findings obtained at rest (p<0,05). Additionally, the right sided H-reflex amplitude was found to be significantly augmented compared to the left side (p<0,05) during facilitation. Significant differences were noted in the H-reflex parameters between male and female subjects both during rest and facilitation. H-reflex latency and the H-M interlatency on both sides were significantly prolonged in male subjects compared to females. Moreover, the M-response amplitudes were markedly augmented in males during the facilitation maneuver (p<0,05). At rest the M-response amplitudes on both sides were larger in males, reaching statistical significance only on the left side (p<0,05). During facilitation the H-reflex amplitudes and Hmax/Mmax ratio were significantly increased in female subjects (p<0,05). Multiple regression analysis revealed that the H-reflex latency showed a significant correlation both with arm length and age. While no relation was found between right-left H-reflex latency differences and age at rest, a significant correlation was apparent (r=0,256, p=0,025) on facilitation. The right-left H-reflex amplitude ratio was inversely correlated with age (r = -0,257, P=0,025). Similarly the H-reflex conduction velocity on both sides decreased with age (right: r=-0,506, p=0,004, left: r=-0,640, p=0,000) both during rest and facilitation.In conclusion it is important to determine the normal reference values for the H-reflex parameters in the assessment of both peripheral and central nervous system disorders. Moreover, in the evaluation of these disorders the most suitable methods and H-reflex parameters should be chosen. H-reflex parameters are affected by the facilitation maneuvers and the supraspinal influences should be taken into account, while performing these tests.