Diffusion restriction in the corticospinal tracts and the corpus callosum in neonates after cerebral insult.

BACKGROUND: In neonatal brains diffusion restriction, which is not limited to the region of insult, but is also found in distant locations from it seems to be a frequent finding, called pre-Wallerian degeneration.

OBJECTIVES: The purpose of this study was to describe these findings and to estimate the frequency of their occurrence with an attempt to determine their clinical significance.

METHODS: 125 brain MRI examinations of neonates with confirmed brain damage performed or consulted in our Institute were retrospectively reviewed, focusing on the presence of restricted diffusion in corticospinal tracts (CST) and corpus callosum (CC). Apparent diffusion coefficients (ADC) were measured in callosal splenium and compared to normal neonatal brains.

RESULTS: Restricted diffusion was found in 21 newborns (16.8%): in 4 in CST (3.2%), in 5 in CC (4.0%), in 12 in both (9.6%). Mean ADC value in CC was 0.638, standard deviation (SD): 0.211μm2 /s and in the control group 0.995, SD: 0.162μm2 /s (p=0,001).

CONCLUSIONS: Neonatal brain MRI should be searched for DWI abnormalities which are not rare and require careful studying of ADC maps. Diffusion restriction in the corpus callosum and/or corticospinal tracts below the region of insult should not be mistaken for acute ischemia as it most likely reflects early phase of secondary neuronal degeneration called pre-Wallerian degeneration. This finding helps in prognostication and guides the management of the affected neonates.