500 Section - Neurophysiological effects of bilateral versus unilateral robot-assisted therapy on brain symmetry in subacute stroke: a pilot randomized controlled trial

Although bilateral robotic therapy has demonstrated benefits for upper limb motor recovery after stroke, its impact on the neural reorganization processes supporting recovery, compared to unilateral robotic therapy, remains insufficiently understood. This pilot randomized controlled study investigated how unilateral and bilateral robotic rehabilitation influences interhemispheric balance in individuals with subacute stroke, assessed through quantitative electroencephalography.

Design: Nineteen participants with ischemic stroke completed a 30-session neurorehabilitation program using a bilateral upper limb robotic exoskeleton, each session lasting 45 minutes, performed daily. Subjects were randomly allocated to either a bilateral treatment group (BG, n = 10) or a unilateral treatment group (UG, n = 9). EEG recordings were obtained before (T0) and immediately after (T0+) the first session, after completion of the intervention (T1), and at a one-week follow-up (T2), under both eyes-open and eyes-closed conditions. The pairwise-derived Brain Symmetry Index (pdBSI) was extracted from EEG data, over the 1–25 Hz frequency range. Clinical outcomes were evaluated at T0 and T1 using validated assessment scales.

Results:

Both treatment groups demonstrated significant improvements in clinical outcomes and interhemispheric symmetry in the 1-25 Hz range following the intervention, with no significant between-group differences. However, only the bilateral group showed a reduction in pdBSI specifically within the delta and theta frequency bands. These neurophysiological changes were not sustained at follow-up, and no significant pdBSI modifications were detected after a single rehabilitation session.

Conclusion:

Our findings demonstrate that robotic rehabilitation is associated with a restoration of the interhemispheric balance in patients with stroke. Distinct modulation patterns between unilateral and bilateral interventions are present in the delta and theta frequency ranges.