Relationships between stroke severity and cortical haemodynamics during hand movement in subacute and chronic stroke survivors

Background: The challenges of upper limb motor rehabilitation post-stroke validate the need for a thorough understanding of haemodynamic changes in the brain. This pilot study investigated the relationships between cortical haemodynamics and arm motor function in subacute and chronic stroke survivors. Methods: Participants in the subacute and chronic stages of stroke recovery aged 25-76 with upper limb impairment subsequent to first middle cerebral artery stroke were recruited. Haemodynamic responses during a hand-tapping task were measured with fNIRS in the sensorimotor cortex of each brain hemisphere. This study examined peak oxyhaemoglobin (HbO), time-to-peak oxyhaemoglobin, trough deoxyhaemoglobin (HbR), time-to-trough deoxyhaemoglobin concentrations and intraregional channel connectivity in relation to arm impairment scores using pearson's correlations. Results: Ten participants were recruited, with arm impairment ranging from mild to severe. In the ipsilesional hemisphere, less arm impairment was associated with longer time-to-peak HbO in the primary motor cortex (r = 0.652, p = 0.041), deeper trough of HbR in the premotor and supplementary motor areas (r = -0.678, p = 0.031) and shallower trough HbR in the dorsolateral prefrontal cortex (r = 0.662, p = 0.037). Additionally, asynchronous activation pattern in intraregional channels was seen in five of the ten participants. Conclusion: This study suggests that cortical haemodynamic variables in the ipsilesional hemisphere may be a useful tool that indexes the severity of arm impairment after stroke