Study of motor and electrophysiological effects induced by the association of motor imagery exercises and Paired Associative Stimulation in 6 hemiplegic patients

ObjectiveMotor imagery (MI) is a cognitive process of imagining a movement without actually doing it. This technique has demonstrated its benefits in the rehabilitation of hemiplegic patients. Non-invasive brain stimulation (NIBS) is still at a preclinical stage but has demonstrated their adjunct effect in the learning of a motor task. In this study, we studied the motor and electrophysiological effects of a session combining Paired Associative Stimulation (PAS), a technique of NIBS and MI exercises (PAS-MI).MethodsA prospective, randomized cross-over study where six patients were included (4 men, age=44.5±13.7 years; 5.7±7.7 months post-stroke). They randomly underwent three 15-minute sessions of stimulation, one week apart: PAS-MI, PAS alone and ShamPAS associated with MI exercises (ShamPAS-MI). The PAS intervention consisted in an electrical stimulation of the hemiplegic extensor carpi radialis (ECR) associated with cortical magnetic stimulation over the wrist motor area. In MI condition, the patient was instructed to imagine extension of his hemiplegic wrist and in ShamPAS intervention, we used a SHAM probe. We compared the surface variation of the motor-evoked potential (MEP) of the ECR and the amplitude of active extension (AE) of the hemiplegic side obtained after each session.ResultsTwenty-five minutes after the end of session PAS alone, an increase of MEP surface (+91%±150.3%) which reveals a higher cortical excitability associated with a slight motor improvement (ΔEA=1.33±3.14°) was shown. A smaller facilitation was shown after sessions PAS-MI and ShamPAS-MI (+45.97±134.32% and 44.85±28.77%, respectively) and, in these cases, was not associated with motor improvement.ConclusionThe session PAS alone seems to induce motor improvement associated with increased cortical excitability not shown after the other two sessions. The combination of two types of stimuli seems to have less effect, perhaps because of the mechanisms regulating the homeostasis of brain plasticity. The results have to be confirmed on a larger sample