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A Piglet Model of Neonatal Hypoxic-Ischemic Encephalopathy
Published on: May 16, 2015
Microstructural Alterations in Projection and Association Fibers in Neonatal Hypoxia-Ischemia
Zuozhen Cao1, Huijia Lin2, Fusheng Gao3
1Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China.
Background:
Diffusion MRI (dMRI) is known to be sensitive to hypoxic-ischemic encephalopathy (HIE). However, existing dMRI studies used simple diffusion tensor metrics and focused only on a few selected cerebral regions, which cannot provide a comprehensive picture of microstructural injury.
Purpose:
To systematically characterize the microstructural alterations in mild, moderate, and severe HIE neonates compared to healthy neonates with advanced dMRI using region of interest (ROI), tract, and fixel-based analyses.
Study Type:
Prospective.
Population:
A total of 42 neonates (24 males and 18 females).
Field Strength/Sequence:
3-T, diffusion-weighted echo-planar imaging.
Assessment:
Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), fiber density (FD), fiber cross-section (FC), and fiber density and cross-section (FDC) were calculated in 40 ROIs and 6 tracts. Fixel-based analysis was performed to assess group differences in individual fiber components within a voxel (fixel).
Statistical Tests:
One-way analysis of covariance (ANCOVA) to compare dMRI metrics among severe/moderate/mild HIE and control groups and general linear model for fixel-wise group differences (age, sex, and body weight as covariates). Adjusted P value < 0.05 was considered statistically significant.
Results:
For severe HIE, ROI-based analysis revealed widespread regions, including the deep nuclei and white matter with reduced FA, while in moderate injury, only FC was decreased around the posterior watershed zones. Tract-based analysis demonstrated significantly reduced FA, FD, and FC in the right inferior fronto-occipital fasciculus (IFOF), right inferior longitudinal fasciculus (ILF), and splenium of corpus callosum (SCC) in moderate HIE, and in right IFOF and left anterior thalamic radiation (ATR) in mild HIE. Correspondingly, we found altered fixels in the right middle-posterior IFOF and ILF, and in the central-to-right part of SCC in moderate HIE.
Data Conclusion:
For severe HIE, extensive microstructural injury was identified. For moderate-mild HIE, association fiber injury in posterior watershed area with a rightward lateralization was found.
Evidence Level:
1 TECHNICAL EFFICACY: Stage 3.
Insights
Advanced diffusion MRI reveals widespread microstructural brain injury in severe hypoxic-ischemic encephalopathy (HIE). Moderate to mild HIE shows specific fiber tract damage, particularly in association fibers with rightward lateralization.
Area of Science:
- Neuroimaging
- Pediatric Neurology
- Radiology
Background:
- Diffusion MRI (dMRI) is sensitive to hypoxic-ischemic encephalopathy (HIE).
- Existing dMRI studies use limited metrics and regional analyses, failing to capture comprehensive microstructural injury.
- Advanced dMRI techniques are needed for detailed characterization of HIE-related brain damage.
Purpose of the Study:
- To systematically characterize microstructural alterations in neonates with mild, moderate, and severe HIE using advanced dMRI.
- To compare findings in HIE neonates with healthy controls.
- To employ region of interest (ROI), tract, and fixel-based analyses for comprehensive assessment.
Main Methods:
- Prospective study of 42 neonates (24 males, 18 females) with varying HIE severity.
- 3-T diffusion-weighted echo-planar imaging was utilized.
- Advanced dMRI metrics (FA, MD, RD, AD, FD, FC, FDC) were calculated in 40 ROIs and 6 tracts, alongside fixel-based analysis.
Main Results:
- Severe HIE showed widespread reduced FA in deep nuclei and white matter.
- Moderate HIE exhibited decreased FC in posterior watershed zones and reduced FA, FD, and FC in specific tracts (IFOF, ILF, SCC).
- Mild HIE demonstrated reduced FA, FD, and FC in the right IFOF and left ATR, with corresponding fixel alterations.
Conclusions:
- Severe HIE involves extensive microstructural brain injury.
- Moderate to mild HIE is associated with specific association fiber injury in the posterior watershed area, showing rightward lateralization.
- Advanced dMRI provides a detailed characterization of HIE-related microstructural damage across different severity levels.
