Purpose or Case Report: To provide radiologic-pathologic correlation of brain injury in the Papez circuit in neonates with hypoxic-ischemic encephalopathy (HIE) and correlate radiologic findings with long-term neurodevelopmental outcomes.
Methods & Materials: A total of 20 full term neonates were evaluated. The cerebral pulsed arterial spin labeling (PASL) values were compared by permutation test to identify brain regions with statistically significant perfusion changes between 14 HIE neonates without evidence of developmental delay by Bayley-III scores(8/6 males/females, mean age 8.2±7.2 days) and 6 HIE neonates with evidence of developmental delay (4/2 males/females, mean age 13.1±8 days). Linear regression was performed to eliminate the effect of age and gender on PASL data. Developmental assessments were carried out at mean (range) age of 16 (6-40) months. The histopathologic studies on specimens were taken from post-mortem brains of another group of infants (1/3 males/females, mean age 10±6.8 days) with HIE. The infants were not the same ones who had MRIs.
Results: Significantly decreased perfusion in the Papez circuit was found in the HIE neonates with developmental delay compared with HIE neonates without findings of delay via Bayley-III. Decreased ASL perfusion values were seen in Papez circuit structures of the fornix (p=0.002), entorhinal cortex (p=0.048), amygdala (p=0.036), hippocampus (p=0.033), and thalamus (p=0.036). In autopsy specimens of neonates with known HIE, anoxic (eosinophilic) neurons, reactive astrocytes, and white matter rarefaction were observed in these regions, providing pathology correlation to the imaging findings of HIE.
Conclusions: The Papez circuit is susceptible to hypoxic-ischemic injury in neonatal patients as demonstrated by perfusion-weighted imaging and histopathology. This sheds new light onto a possible non-familial mechanism of neuropsychiatric disease evolution initiated in the infant period and raises the potential for early identification of at-risk children who could benefit from further surveillance and interventions.