1996 Volume 33 Issue 6 Pages 407-415
We used transcranial magnetic stimulation to record motor evoked potentials (MEP) from the lower limb muscles in 33 patients with cerebrovascular diseases (CVD) and 20 normal subjects. MEPs were recorded from the abductor hallucis (AH) muscles both at rest and during mild contraction of the muscles. The central motor conduction time (CMCT) was calculated by subtracting the peripheral conduction segment, measured using the shortest latency F wave recorded in the AH, from the MEP onset latency. Amplitude of the MEP was expressed as MEP/M wave amplitude ratio. Compared with the unaffected side, CMCT was significantly prolonged and the MEP/M wave amplitude ratio was significantly lower on the affected side in the patients. In some patients with severe hemiparesis, no response was obtained on the affected side, even under the facilitated condition with contraction of the muscles. There was no significant difference between the MEP characteristics on the right and left sides in normal subjects. With the exception of the MEP/M wave amplitude ratio in relaxed AH muscle, these characteristics in affected limbs correlated significantly with the extent of volitional movement of those limbs. This test was valuable to evaluate the level of hemiparesis without being influenced by abnormal synergic movements. The present study indicated that the value of these MEP characteristics may serve as important parameters in evaluating functional recovery of paretic limbs in hemiparetic patients.
