Evaluation of posterior tibial H/M ratio in cerebrovascular accidents

Clinical use of the late responses during routine neurophysiological examination has significantly increased the diagnostic yield of the neurophysiological evaluation. The H max to M max ratio (H/M ratio) is considered a suitable index for illustrating the level of reflex excitability of the motor pool. In this study posterior tibial nerve H/M ratio changes in cerebrovascular accidents (CVA) evaluated. This investigation was carried out in 22 normal subjects aged 40-65 years with mean 52 years, and in 40 patients with CVA aged 42-63 years with mean 57 years. In normal subjects no significant differences were found between the mean values observed between right and left sides. In patients significant increased H/M ratios in both sides with more in non-plegic leg (P<0.01) were found. The facilitation of Babinsky sign in patients is significantly associated with low H/M ratios (P=0.003). The H/M ratio changes were not significantly associated with severity of hemiplegia (P=0.3 for lower extremities, P=0.9 for upper extremities). The H/M ratio was increased in ischemic lesions (P<0.01), but in intracerebral hemorrhages the soleus H/M ratio increases in non-plegic side the same as the plegic side. The posterior tibial nerve H/M ratios are increased in CVA bilaterally due to decreased presynaptic inhibition Ia terminals, thus amplitude of H reflexes increased without increased amplitude of M response.