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 (р>0,05).
In the remaining compared subgroups, positive interhemispheric
correlation 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 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 (p<0.02).
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.
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