Diffusion Tensor Tractography of the Corticospinal Tracts in Neonates after Hypoxic Ischemic Encephalopathy

Background: MRI scans of infants who suffered from neonatal hypoxic ischemic encephalopathy (HIE) are considered to be the best proxy for prediction of long-term neurodevelopmental outcome. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) are quantitative MRI techniques that generate vectors that visualize and model neuronal fiber tracts within the brain.

Objective: To evaluate the associations of corticospinal tracts’ (CST) diffusion values with the degree of MRI brain injury in infants with neonatal HIE born after 35w gestation.

Methods: Retrospective study of a prospectively enrolled cohort of infants with neonatal HIE born between 2014-2020 that had an early MRI. Scans were prospectively scored for degree of brain injury according to the Rutherford scoring system. Explore DTI software was used for CST tractography and for computation of their volume, fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Neonatal data for seizures, abnormal aEEG, abnormal neurologic status at discharge, or death was retrieved.

Results: Sixty-six infants were included in the study. Significant associations were found between a worse MRI score and a longer hospital stay (p=0.002), seizures (p=0.012), abnormal aEEG background (p<0.001), abnormal neurologic status at discharge (p<0.001) and death (p=0.001). A significant negative association was found between a higher MRI category score, tract volume and diffusion values.

Conclusions: Decrease in diffusion values of the CST is associated with a higher likelihood of worse MRI category scores. These findings support a possible prognostic role CST tracts diffusion value.