I studied a secondary disturbance of the peripheral nerve following a lesion in the upper motoneuron using M and F wave studies of the tibial nerve. Fifteen subjects with hemiplegia as a result of cerebral palsy (CP), 15 subjects with hemiplegia as a result of strokes or head injuries (acquired group), and 15 normal controls age-matched to the CP group were examined. I assessed the MCV and the amplitude ratio of M waves after stimulating the popliteal and ankle. The shortest latency, difference in latencies, and the duration and amplitude of F waves after stimulating the ankle were also assessed. When the affected and the non-affected limbs were compared, both the CP and the acquired group had statistically significant differences in the MCV, F/M duration ratio and F/M amplitude ratio. When the results for non-affected limbs and the normal group were compared, both the CP and the acquired group had statistically significant differences for the MCV, the shortest F latency, and the F/M duration ratio. In both the affected and non-affected limbs, the abnormal M wave amplitude ratio and the F/M amplitude ratio in the CP group were less severe than those of the acquired group.
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