Search for Approaches to the Strategy of Transcranial Neuromodulation in Patients with Post-Stroke Hemiparesis in Real Clinical Practice

Background: In order to increase the efficiency of motor recovery after a stroke in routine clinical practice, the search for selective biomarkers that determine the choice of the optimal strategy for non-invasive neuromodulation of the brain remains relevant. The study of patterns of interhemispheric interaction can hypothetically help in determining the correct conceptual model of neuromodulation. Aims: To determine variants of interhemispheric interaction based on a correlation analysis of motor cortex excitability in subgroups of patients with post-stroke hemiparesis stratified by the degree of motor deficit. Materials and methods: The retrospective observational study involved 185 people (men (56.2%) and women (43.8%) aged 19 to 88 years) with verified post-stroke hemiparesis and 40 healthy volunteers (men (55.0%) and women (45.0%) aged 20 to 85). The patients underwent diagnostic transcranial magnetic stimulation in the projection of the cortical representation of m. Abductor pollicis brevis and m. Tibialis anterior of both brain hemispheres. The level of excitability of the motor cortex and its interhemispheric asymmetry were recorded, followed by correlation analysis in subgroups stratified by the degree of paresis. Results: It was revealed that there was no interhemispheric correlation of rest motor thresholds (rMT) in patients with a level of muscle strength for the “hand” segment of 0-2 points (р0,05). In the remaining compared subgroups, positive interhemispheric correlation of the rMT were noted (p0.02). A positive correlation of the rMT of the damaged brain hemisphere and interhemispheric asymmetry of the motor cortex excitability for all degrees of paresis was observed when studying the cortical representation of the muscles of the upper limbs. A negative correlation between rMT of the unaffected brain hemisphere and interhemispheric asymmetry was detected for all degrees of motor deficit of the “foot” segment (p0.02). Conclusions: The study did not confirm the concept of interhemispheric competition of the studied functional activity of the brain. Three authentic variants of interhemispheric interaction were identified: unidirectional hemispheric interaction with predominant reactivity of the affected hemisphere; unidirectional hemispheric interaction with predominant reactivity of the unaffected hemisphere; functional interhemispheric dissociation. The results obtained indicate the need to rethink some approaches to transcranial neuromodulation strategies.