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Investigating microbleeds and white matter hyperintensities in TBI at a tract-level: A DTI study
Zalán Petneházy1, Dávid Bognár1, Péter Laar1
1Department of Medical Imaging, University of Pécs, Clinical Centre, Hungary; National Laboratory of Translational Neuroscience, Hungary; University of Pécs, Medical School, Hungary.
Objectives:
This study aimed to determine whether focal MRI lesions such as microbleeds (MBs) and focal white matter hyperintensities (FWMHs) serve as reliable and specific markers for tract-level white matter injury in traumatic brain injury (TBI).
Materials & Methods:
Twenty-two patients with moderate-to-severe TBI and 22 age-matched healthy controls underwent MRI on a 3 T Siemens Prisma scanner. Imaging included susceptibility-weighted imaging (SWI), fluid-attenuated inversion recovery (FLAIR), and diffusion tensor imaging (DTI). Focal lesions were manually identified on SWI and FLAIR and mapped onto tractography reconstructions. Diffusion metrics-fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were compared between lesion-affected tracts, contralateral normal-appearing white matter (NAWM), and corresponding control tracts. Statistical analyses were performed using repeated measures ANOVA with Greenhouse-Geisser correction and Bonferroni-adjusted post hoc tests for FA. Friedman tests were conducted for MD, AD, and RD, followed by Bonferroni-corrected Wilcoxon post hoc comparisons.
Results:
In this study, we identified 27 MBs and 66 FWMHs intersecting white matter tracts. We observed notable differences in diffusion metrics when comparing lesion-affected tracts to healthy controls. In MB-affected tracts, fractional anisotropy (FA) differed significantly (p = 0.002), while mean diffusivity (MD) also showed a significant alteration (p = 0.002), along with radial diffusivity (RD) (p < 0.001). Similarly, in FWMH-affected tracts, significant differences were observed in FA (p < 0.001), MD (p < 0.001), axial diffusivity (AD) (p < 0.001), and RD (p < 0.001). However, we did not find any significant differences between lesion-affected tracts and the contralateral normal-appearing white matter (NAWM).
Conclusion:
MBs and FWMHs do not co-localize with axonal injury at the tract level but indicate a global white matter damage.
Insights
Focal MRI lesions like microbleeds and white matter hyperintensities in traumatic brain injury (TBI) do not specifically mark axonal injury. These findings suggest they indicate broader white matter damage rather than localized tract damage.
Area of Science:
- Neuroimaging
- Traumatic Brain Injury Research
- White Matter Pathology
Background:
- Traumatic brain injury (TBI) can cause diffuse white matter damage.
- Identifying specific MRI markers for tract-level injury is crucial for understanding TBI pathology.
- Microbleeds (MBs) and focal white matter hyperintensities (FWMHs) are common MRI findings in TBI.
Purpose of the Study:
- To investigate if MBs and FWMHs are reliable markers of tract-level white matter injury in TBI.
- To compare diffusion metrics in lesion-affected tracts versus normal-appearing white matter and controls.
Main Methods:
- MRI including SWI, FLAIR, and DTI was performed on 22 TBI patients and 22 controls.
- Focal lesions (MBs, FWMHs) were identified and mapped onto white matter tracts.
- Diffusion metrics (FA, MD, AD, RD) were analyzed in affected tracts, contralateral NAWM, and control tracts.
Main Results:
- Significant alterations in FA, MD, and RD were found in MB-affected tracts compared to controls.
- Significant differences in FA, MD, AD, and RD were observed in FWMH-affected tracts versus controls.
- No significant differences were detected between lesion-affected tracts and contralateral normal-appearing white matter (NAWM).
Conclusions:
- MBs and FWMHs do not directly correlate with axonal injury at the tract level in TBI.
- These focal lesions appear to reflect more global white matter damage.
- Further research is needed to elucidate the precise mechanisms of white matter injury in TBI.
