Magnetic Resonance Imaging Findings of Term and Preterm Hypoxic-Ischemic Encephalopathy: A Review of Relevant Animal Models and Correlation to Human Imaging.

Kyle A Jisa,Eric S Peeples,Dillon D Clarey

doi:10.2174/1874440001812010055

Abstract

Background:Neonatal hypoxic-ischemic encephalopathy is brain injury caused by decreased perfusion and oxygen delivery that most commonly occurs in the context of delivery complications such as umbilical cord compression or placental abruption. Imaging is a key component for guiding treatment and prediction of prognosis, and the most sensitive clinical imaging modality for the brain injury patterns seen in hypoxic-ischemic encephalopathy is magnetic resonance imaging.Objective:The goal of this review is to compare magnetic resonance imaging findings demonstrated in the available animal models of hypoxic-ischemic encephalopathy to those found in preterm (≤ 36 weeks) and term (>36 weeks) human neonates with hypoxic-ischemic encephalopathy, with special attention to the strengths and weaknesses of each model.Methods:A structured literature search was performed independently by two authors and the results of the searches were compiled. Animal model, human brain age equivalency, mechanism of injury, and area of brain injury were recorded for comparison to imaging findings in preterm and term human neonates with hypoxic-ischemic encephalopathy.Conclusion:Numerous animal models have been developed to better elicit the expected findings that occur after HIE by allowing investigators to control many of the clinical variables that result in injury. Although modeling the same disease process, magnetic resonance imaging findings in the animal models vary with the species and methods used to induce hypoxia and ischemia. The further development of animal models of HIE should include a focus on comparing imaging findings, and not just pathologic findings, to human studies.

Highlights

Neonatal Hypoxic-Ischemic Encephalopathy (HIE) is a condition resulting from decreased blood flow and oxygen delivery to the brain, which generally occurs at or around the time of delivery
Numerous animal models have been developed to better elicit the expected findings that occur after HIE by allowing investigators to control many of the clinical variables that result in injury
Modeling the same disease process, magnetic resonance imaging findings in the animal models vary with the species and methods used to induce hypoxia and ischemia

Summary

Introduction

Neonatal Hypoxic-Ischemic Encephalopathy (HIE) is a condition resulting from decreased blood flow and oxygen delivery to the brain, which generally occurs at or around the time of delivery. Various animal models have been developed to examine changes within the brain during Hypoxic-Ischemic (HI) injury, as well as to test novel therapies. Use of these models allows for controlling multiple variables that can impact the severity of HI injury, including developmental maturity at the time of. Various animal models have been utilized for inducing cerebral ischemia, but there have only been a few studies that have focused on imaging these animals with HIE [2, 4 - 10] Translating these studies to human populations is difficult due to the need to adjust for different rates of brain maturation between species, complicated by the fact that MRI findings in animals vary based on the species and method of inducing hypoxia and ischemia. Imaging is a key component for guiding treatment and prediction of prognosis, and the most sensitive clinical imaging modality for the brain injury patterns seen in hypoxic-ischemic encephalopathy is magnetic resonance imaging

Methods

Discussion

Conclusion