Post-Ischemia Functional Rehabilitation: Morphological Correlates to Diffusion Kurtosis Imaging in Neural Plasticity
Nelson, Andrew W.
Milliken, Garrett W.
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Loss of contra-lesion forelimb motor function is one of the most common impairments resulting from ischemic stroke. Rehabilitation strategies may augment mechanisms of spontaneous recovery of motor function within a time-dependent window following stroke. The structural and morphological underpinnings of these mechanisms are poorly understood, however. Diffusional kurtosis imaging (DKI) has been shown to possess advantages over other conventional neuroimaging techniques in assessment of post-stroke changes in tissue microenvironments. Measurements of mean kurtosis (MK) and mean diffusivity (MD) in infarct tissue may be referenced in investigating microstructural tissue changes during stroke progression in order to establish biomarkers to be used in assessing functional rehabilitation outcome. This pair of studies investigated changes in axonal surface density as a potential biomarker that reflects MD and MK evolution within the penumbral region of infarct SMC in controlled rat models of acute and chronic stroke, with an additional effect of rehabilitation investigated in the chronic stage. Overall, no significant relationships between axonal surface density and either MD or MK were found. Additionally, no significant changes in axonal surface density were observed in acute stroke progression or in the chronic stroke period as a result of functional motor rehabilitation. These results suggest that the SMI-312 antibody used to visualize axons was insufficiently sensitive in capturing structural changes in axons following stroke, or that axonal surface density is not a viable biomarker responsible for changes in DKI observed in acute and chronic stroke progression. As such, future studies should reexamine axonal surface density in the penumbra following stroke using an antibody more specific to small, demyelinated axons.