[Reflex responses from the sural nerve to tibialis anterior muscle in hemiplegic patients: the relation between the responses and Babinski sign].

Stimulation of the sural nerve of healthy subjects induced short latency inhibition in the ipsilateral tibialis anterior muscle and facilitation in peroneal muscle. We examined lower limb muscle responses after stimulation of the sural nerve in 19 patients with hemiplegia caused by cerebro-vascular disease and compared them with the control responses. The sural nerve was stimulated electrically (3 or 5 square wave pulses of 0.5 ms repeated at 250 Hz) during weak tonic contraction. Stimulation was triggered to average the rectified surface electromyography (EMG) of the test muscle. Usually 100 - 200 sweeps were averaged. After stimulation, the tibialis anterior muscle on the affected side of the hemiplegic patients showed the patterns of inhibition, facilitation, and no response, whereas all responses on the unaffected side, except those of one patient, were inhibition. The peroneal muscle on both sides showed only facilitation as in the controls. Abnormal responses of the tibialis anterior muscle on the affected side were present in many patients who had the Babinski sign. Abnormal responses in the tibialis anterior muscle of the affected side may have been due to contributions by disinhibition of the flexor reflex, late-recruited motor units or both.