Abstract
Twenty hemipiegic patients were studied with transcranial magnetic stimulation (TMS).
Motor evoked potentials (MEPs) of the biceps brachii (BB) and the abductor pollicis
brevis muscles (APB) were recorded on both sides simultaneously. TMS was carried out
with an 8-shaped coil over different scalp positions in the intact hemisphere. Bilateral
MEPs of BB were elicited in patients with later childhood lesion as well as early
lesion, but those of APB were only elicited in the latter (up to 2 years). In patients
with prenatal or birth lesion on BB and in all patients on APB, cortical maps of MEP
amplitude of paretic and non-paretic sides showed similar distributions. There were
no remarkable differences in mean latency between both sides, and correlation coefficients
of MEP amplitude between both sides were high in these patients. In patients with
postnatal lesion on BB, MEP maps of both sides showed different distributions, ipsilateral
MEP latencies were delayed and correlation coefficients were low. We suspect that
ipsilateral MEPs after early lesion derive from axonal sprouting both in the proximal
and the distal muscles. After postnatal lesion, other mechanisms of ipsilateral motor
projection take place in the proximal muscles, but not in the distal ones.
Key words
Plasticity - Hemiplegia - Children - Magnetic stimulation
