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.
Highlights
Complete recovery of motor function after stroke is rare with deficits persisting into the chronic phase of recovery
Mean fractional anisotropy (FA) for the sensory region of the corpus callosum (CC) was significantly reduced compared to the healthy group (F(1, 21) = 15.37, p = 0.001), but a significant difference was not observed between groups for CC motor region mean FA (F(1, 21) = 1.48, p = 0.236) (Figure 1)
Age was significantly correlated with Fugl-Meyer (FM) score (r = −0.571, p = 0.041), Wolf Motor Function Test (WMFT) asymmetry (r = 0.571, p = 0.042), grip strength asymmetry (r = 0.653, p = 0.021), Box and Blocks test (BBT) asymmetry (r = 0.687, p = 0.010), and contralesional posterior limb of the internal capsule (PLIC) FA (r = −0.668, p = 0.013)
Summary
Complete 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. FA is a quantitative, unit-less measure of the directionality of water diffusion that indexes the microstructural properties of white matter [11] Using this measure, relationships between white matter integrity and various measures of motor function have been demonstrated [6,7,8,9,10]. The present experiments were designed to explore differences in the integrity of motor and sensory fibers of the CC and motor output tracts of the PLIC between individuals with stroke and healthy age-matched controls, and to evaluate how these measures relate to multiple dimensions of motor recovery
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