Microstructural Alterations in Projection and Association Fibers in Neonatal Hypoxia-Ischemia

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.