Both projection and commissural pathways are disrupted in individuals with chronic stroke: investigating microstructural white matter correlates of motor recovery

Abstract

BackgroundComplete recovery of motor function after stroke is rare with deficits persisting into the chronic phase of recovery. Diffusion tensor imaging (DTI) can evaluate relationships between white matter microstructure and motor function after stroke. The objective of this investigation was to characterize microstructural fiber integrity of motor and sensory regions of the corpus callosum (CC) and descending motor outputs of the posterior limb of the internal capsule (PLIC) in individuals with chronic stroke and evaluate the relationships between white matter integrity and motor function.ResultsStandardized measures of upper extremity motor function were measured in thirteen individuals with chronic stroke. Manual dexterity was assessed in thirteen healthy age-matched control participants. DTI scans were completed for each participant. Fractional anisotropy (FA) of a cross-section of sensory and motor regions of the CC and the PLIC bilaterally were quantified. Multivariate analysis of variance evaluated differences between stroke and healthy groups. Correlational analyses were conducted for measures of motor function and FA. The stroke group exhibited reduced FA in the sensory (p = 0.001) region of the CC, contra- (p = 0.032) and ipsilesional (p = 0.001) PLIC, but not the motor region of the CC (p = 0.236). In the stroke group, significant correlations between contralesional PLIC FA and level of physical impairment (p = 0.005), grip strength (p = 0.006) and hand dexterity (p = 0.036) were observed.ConclusionsMicrostructural status of the sensory region of the CC is reduced in chronic stroke. Future work is needed to explore relationships between callosal sensorimotor fiber integrity and interhemispheric interactions post-stroke. In addition, contralesional primary motor output tract integrity is uniquely and closely associated with multiple dimensions of motor recovery in the chronic phase of stroke suggesting it may be an important biomarker of overall motor recovery.

Integrity of normal-appearing white matter and functional outcomes after acute ischemic stroke

“…Fourth, we elected to assess median values of the selected diffusivity metrics within contralesional NAWM rather than targeting a specific region of interest, as has been done in some prior studies. 41,42 While region-of-interest analysis is important for tract-specific changes, we draw from the established methodology of a global assessment of NAWM integrity that proved to be more informative with regard to the complex functional assessments in the general population and is likely to have a broader role in the studies of poststroke recovery. 7,21,41 The variability in the number of diffusion-encoding gradient directions and number of excitations could potentially introduce error in the DTI acquisition; however, this was previously reported to not significantly affect mean FA or MD measurements despite slight differences in the individual eigenvalues.…”

Compensatory motor network connectivity is associated with motor sequence learning after subcortical stroke

“…In addition, age, post-stroke duration and Fugl Meyer (FM) were correlated with predictor weights as these measures have been previously shown to have a strong relationship with neurophysiological measures, such as white matter integrity (fractional anisotropy; FA) [25]. All statistical procedures were conducted using SPSS software (SPSS 19.0).…”

Leukoaraiosis Predicts a Poor 90-Day Outcome after Endovascular Stroke Therapy

“…For example, decreased integrity of fiber tracts within the unaffected hemisphere and purported compensatory pathways (such as the corticorubrospinal system) have been shown to impair poststroke recovery. 23,24 Accordingly, global white matter changes such as those caused by leukoaraiosis are expected to adversely affect the potential for poststroke recovery. However, although several studies have linked leukoaraiosis to poor functional outcomes, there is a paucity of data regarding the degree of poststroke recovery, particularly in patients with large-artery occlusion.…”