Motor evoked potentials in stroke patients during neurorehabilitative approaches

Excitability and conductivity of the central motor system were evaluated through transcranial magnetic stimulation in stroke patients. We foilowed-up two rehabilitation approaches having a different theoretical frame ("peripheral" i.e. Bobath versus "central" i.e. Perfetti approach). According to perceptual theories, voluntary movement and relaxation act at a "central" level activating brain mechanisms of perceptual awareness and purposeful behaviour (cortical facilitation). On the other hand, "peripheral" facilitatory techniques utilise movement control strategies acting at a spinal level. Twenty patients were selected: 11 and 9 were following a neurorehabilition treatment based on Bobath or Perfetti approaches, respectively. Functional and neurological status was evaluated. MEPs was bilaterally recorded from five upper limb muscles (Deltoid, FCR, EDC, FDI, ADM) in 5 different sessions, from admittance (TO) to 3-4 months away from TO (T4). In Perfetti-treated patients, a MEPs amplitude increment was present in most muscles at rest and during contraction. On the other hand, considering mean MEP latencies, it was possible to find shorter latencies, either at rest or during contraction in the Bobath-treated population. After a vascular monohemispheric lesion, the analysis of 5 different MEP recording session, showed some differences between Bobathand Perfetti-treated patients: in Perfetti group, a pattern of amplitude increment and SP shortening was evident, while on Bobath group there was a shortening of latencies. Excitability thresholds were not different in the two groups. It seems that an approach based on "peripheral" afferences modulation (Bobath) induces some recovery of the lost tonic facilitatory sensory feed-back from the affected arm. The "central" method (Perfetti), acting at a cortical level, could contribute to a decrement of inhibition from the affected hemisphere coupled with a more synchronized recruitment of the motoneuronal population (temporal summation) as well as of an increased number of the activated cortical efferents (spatial summation).