Dataset Information

Comparison of corticospinal tract integrity measures extracted from standard versus native space in chronic stroke.

ABSTRACT:

Background

Fractional anisotropy (FA) and mean diffusivity (MD) are measures derived from diffusion-weighted imaging that represent the integrity of the corticospinal tract (CST) after stroke. Some studies of the motor system after stroke extract FA and MD from native space while others extract from standard space making comparison across studies challenging.

New method

The purpose was to compare CST integrity measures extracted from standard versus native space in individuals with chronic stroke. Twenty-four individuals with stroke underwent diffusion-weighted imaging and motor impairment assessment. The spatial location of the CST was identified using four commonly utilized approaches; therefore, our results are applicable to a variety of approaches.

Results

FA extracted from standard space (FA_std) was significantly different from FA extracted from native space (FA_nat) for all four approaches; FA_std was greater than FA_nat for three approaches. The relationship between ipsilesional CST FA and UE FM was significant for all approaches and similar regardless of extraction space. MD_std was significantly different from MD_nat for most approaches, however, the directionality of the differences was not consistent.

Comparison with existing method(s)

Our study shows that extraction space influences diffusion-based microstructural integrity values (FA and MD) of the CST in individuals with stroke, which is important when considering methods for aggregating CST integrity data across studies. The relationship between CST integrity and motor impairment appears to be robust to extraction space.

Conclusions

The differences we identified are important for comparing FA and MD values across studies that use different extraction space. Our results provide context for future meta-analyses of diffusion-based metrics of CST integrity in individuals with stroke.

SUBMITTER: Lewis AF

PROVIDER: S-EPMC8205992 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature

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Publications

Comparison of corticospinal tract integrity measures extracted from standard versus native space in chronic stroke.

Lewis Allison F AF Stewart Jill C JC

Journal of neuroscience methods 20210507

<h4>Background</h4>Fractional anisotropy (FA) and mean diffusivity (MD) are measures derived from diffusion-weighted imaging that represent the integrity of the corticospinal tract (CST) after stroke. Some studies of the motor system after stroke extract FA and MD from native space while others extract from standard space making comparison across studies challenging.<h4>New method</h4>The purpose was to compare CST integrity measures extracted from standard versus native space in individuals wit ...[more]

PMID: 33971202

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Project description:ObjectiveStudies on upper limb recovery following stroke have highlighted the importance of the structural and functional integrity of the corticospinal tract (CST) in determining clinical outcomes. However, such relationships have not been fully explored for the lower limb. We aimed to test whether variation in walking impairment was associated with variation in the structural or functional integrity of the CST.MethodsTranscranial magnetic stimulation was used to stimulate each motor cortex while EMG recordings were taken from the vastus lateralis (VL) bilaterally; these EMG measures were used to calculate both ipsilateral and contralateral recruitment curves for each lower limb. The slope of these recruitment curves was used to examine the strength of functional connectivity from the motor cortex in each hemisphere to the lower limbs in chronic stroke patients and to calculate a ratio between ipsilateral and contralateral outputs referred to as the functional connectivity ratio (FCR). The structural integrity of the CST was assessed using diffusion tensor MRI to measure the asymmetry in fractional anisotropy (FA) of the internal capsule. Lower limb impairment and walking speed were also measured.ResultsThe FCR for the paretic leg correlated with walking impairment, such that greater relative ipsilateral connectivity was associated with slower walking speeds. Asymmetrical FA values, reflecting reduced structural integrity of the lesioned CST, were associated with greater walking impairment. FCR and FA asymmetry were strongly positively correlated with each other.ConclusionsPatients with relatively greater ipsilateral connectivity between the contralesional motor cortex and the paretic lower limb were more behaviorally impaired and had more structural damage to their ipsilesional hemisphere CST.SignificanceMeasures of structural and functional damage may be useful in the selection of therapeutic strategies, allowing for more tailored and potentially more beneficial treatments.

Project description:BackgroundPreserved integrity of the corticospinal tract (CST) is a marker of good upper-limb behavior and recovery following stroke. However, there is less understanding of neural mechanisms that might help facilitate upper-limb motor recovery in stroke survivors with extensive CST damage.ObjectiveThe purpose of this study was to investigate resting state functional connectivity in chronic stroke survivors with different levels of CST damage and to explore neural correlates of greater upper-limb motor performance in stroke survivors with compromised ipsilesional CST integrity.MethodsThirty chronic stroke survivors (24 males, aged 64.7 ± 10.8 years) participated in this study. Three experimental sessions were conducted to: 1) obtain anatomical (T1, T2) structural (diffusion) and functional (resting state) MRI sequences, 2) determine CST integrity with transcranial magnetic stimulation (TMS) and conduct assessments of upper-limb behavior, and 3) reconfirm CST integrity status. Participants were divided into groups according to the extent of CST damage. Those in the extensive CST damage group did not show TMS evoked responses and had significantly lower ipsilesional fractional anisotropy.ResultsOf the 30 chronic stroke survivors, 12 were categorized as having extensive CST damage. Stroke survivors with extensive CST damage had weaker functional connectivity in the ipsilesional sensorimotor network and greater functional connectivity in the ipsilesional fronto-parietal network compared to those with preserved CST integrity. For participants with extensive CST damage, improved motor performance was associated with greater functional connectivity of the ipsilesional fronto-parietal network and higher fractional anisotropy of the ipsilesional rostral superior longitudinal fasciculus.ConclusionsStroke survivors with extensive CST damage have greater resting state functional connectivity of an ipsilesional fronto-parietal network that appears to be a behaviorally relevant neural mechanism that improves upper-limb motor performance.

Project description:ObjectiveThe primary objective of this study was to retrospectively investigate associations between clinical magnetic resonance imaging-based (MRI) metrics of corticospinal tract (CST) status and paretic upper extremity (PUE) motor recovery in patients that completed acute inpatient rehabilitation (AR) post-stroke.MethodsWe conducted a longitudinal chart review of patients post-stroke who received care in the Emory University Hospital system during acute hospitalization, AR, and outpatient therapy. We extracted demographic information, stroke characteristics, and longitudinal documentation of post-stroke motor function from institutional electronic medical records. Serial assessments of paretic shoulder abduction and finger extension were estimated (E-SAFE) and an estimated Action Research Arm Test (E-ARAT) score was used to quantify 3-month PUE motor function outcome. Clinically-diagnostic MRI were used to create lesion masks that were spatially normalized and overlaid onto a white matter tract atlas delineating CST contributions emanating from six cortical seed regions to obtain the percentage of CST lesion overlap. Metric associations were investigated with correlation and cluster analyses, Kruskal-Wallis tests, classification and regression tree analysis.ResultsThirty-four patients met study eligibility criteria. All CST overlap percentages were correlated with E-ARAT however, ventral premotor tract (PMv) overlap was the only tract that remained significantly correlated after multiple comparisons adjustment. Lesion overlap percentage in CST contributions from all seed regions was significantly different between outcome categories. Using MRI metrics alone, dorsal premotor (PMd) and PMv tracts classified recovery outcome category with 79.4% accuracy. When clinical and MRI metrics were combined, AR E-SAFE, patient age, and overall CST lesion overlap classified patients with 88.2% accuracy.ConclusionsStudy findings revealed clinical MRI-derived CST lesion overlap was associated with PUE motor outcome post-stroke and that cortical projections within the CST, particularly those emanating from non-M1 cortical areas, prominently ventral premotor (PMv) and dorsal premotor (PMd) cortices, distinguished between PUE outcome groups. Exploratory predictive models using clinical MRI metrics, either alone or in combination with clinical measures, were able to accurately identify recovery outcome category for the study cohort during both the acute and early subacute phases of post-stroke recovery. Prospective studies are recommended to determine the predictive utility of including clinical imaging-based biomarkers of white matter tract structural integrity in predictive models of post-stroke recovery.

Dataset Information

Comparison of corticospinal tract integrity measures extracted from standard versus native space in chronic stroke.

Background

New method

Results

Comparison with existing method(s)

Conclusions

Publications

Comparison of corticospinal tract integrity measures extracted from standard versus native space in chronic stroke.

Similar Datasets

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