• clinical neurophysiology
• cortical excitability
• functional recovery
• intracortical inhibition
• motor evoked potentials
• neurorehabilitation
• silent period
• stroke

New frontiers in stroke rehabilitation aim to improve functional recovery taking advantage from the knowledge of mechanisms of cortical reorganization that occur after the acute event. There are several aspects still to be explored in this field. On the one hand, the role of contralesional primary motor cortex in post-stroke recovery is still debated. It was supposed that unaffected hemisphere operates at a higher-order processing level involved in selection, preparation, temporal or spatial organization of movement, facilitating control of recovered motor function, but no clear correlation between unaffected hemisphere activity, clinical function and motor recovery has been carried out in subacute stroke patients. On the other hand, recent literature suggests to apply a stratification based on lesion location and to consider patients with cortico-subcortical and subcortical strokes separately: different lesion location may influence therapeutic response. Therefore we aimed to describe the contribution of UH in plastic phenomena after stroke and to identify a neurophysiological parameter that can be used as marker to describe motor recovery in subacute stroke patients with different lesion location. In particular we focused on Silent Period (SP), since both shortened and prolonged SP durations have been proposed as negative prognostic factors for motor recovery after stroke. A crucial question is the lack of information about SP modifications basing on specific factors that may influence its length. One of these factors is the simultaneous assumption of drug therapies used for the management of neurological and psychiatric disorders. Furthermore, a possible confounding factor is the type and the amount of motor activity performed by subjects.
Following these considerations, in the first part of this study we correlated neurophysiological and functional features in a cohort of stroke patients recruited in a specific time window from the acute event and subdivided in cortico-subcortical and subcortical strokes. Evaluations were also performed at 3 months after stroke to monitor changes in brain reorganization and clinical behaviour. Our main finding was that 3 months after the acute event patients affected by subcortical stroke presented a reduction in contralateral SP duration in the unaffected hemisphere; this trend was related to clinical improvement of upper limb motor function. Therefore, the reduction of unaffected intracortical inhibition in subcortical stroke patients may play an important role in effective motor recovery.
In the second part of this project we performed a retrospective study aimed to deeply comprehend the influence of CNS drugs, in particular GABAergic, on motor recovery in stroke patients. We found that assumption of GABAergic drugs impacts on motor recovery in the subacute phase of stroke: subdividing patients on the basis of drug therapies assumption during rehabilitation treatment, we observed a better clinical performance in patients who did not assumed GABAergic drugs, correlated to a reduction of intracortical inhibition in unaffected hemisphere. Such findings could potentially provide insights into the mechanisms of stroke recovery, and might also help strategic planning in the design of therapeutic approaches to improving motor recovery after stroke.
In the third part of the study we used a standardized robotic-aided rehabilitative protocol to investigate the neurophysiological correlates of the motor learning process. To do this, we quantified SP modifications in subacute stroke patients related to clinical performance after a specific rehabilitative protocol. Our results showed a direct correlation between the intracortical inhibition in unaffected hemisphere and the functional improvement on upper limb, highlighting the possible direct involvement of the unaffected hemisphere in relearning of new skills and improvement of motor functions.
In conclusion, the deeper knowledge of the mechanisms involved in motor recovery may help to structure specific therapeutic protocols, maximizing the effects of the rehabilitation and allowing visible results.