Search for approaches to transcranial neuromodulation in patients with post-stroke hemiparesis in real clinical practice

BACKGROUND: 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 noninvasive neuromodulation of the brain remains relevant. The study of interhemispheric interaction patterns can hypothetically help in determining the correct conceptual model of neuromodulation. AIM: To determine variants of interhemispheric interaction based on a correlation analysis of motor cortex excitability in patients with poststroke hemiparesis stratified by the degree of motor deficit. MATERIALS AND METHODS: This retrospective observational study involved 185 people (men, 56.2%; women, 43.8%) aged 19–88 years with verified poststroke hemiparesis and 40 healthy volunteers (men, 55.0%; women, 45.0%) aged 20–85 years. 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 excitability level of the motor cortex and its interhemispheric asymmetry were recorded, and correlation analysis in subgroups stratified by the degree of paresis was performed. RESULTS: No interhemispheric correlation of resting motor thresholds (rMT) was found in patients with a level of muscle strength for the “hand” segment of 0–2 points (р >0.05). In the remaining subgroups, positive interhemispheric correlations of the rMT were noted (p <0.02). 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 evaluating the cortical representation of the upper limb muscles. A negative correlation between the rMT of the unaffected brain hemisphere and interhemispheric asymmetry was detected for all degrees of motor deficit of the “foot” segment (p <0.02). CONCLUSION: 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, and functional interhemispheric dissociation. The results indicate the need to rethink some approaches to transcranial neuromodulation strategies in the analyzed cohort.