Purpose or Case Report:
Hypoxic ischemic encephalopathy (HIE) is one of the most common causes of neurological injury in neonates. Given the variability of clinical manifestations, ranging from normal neurological outcomes to profound neurocognitive impairment or death, precise characterization is critical in prognostication. Evaluation is made more challenging by the unique morphologic features of the neonatal brain which constantly evolve as the nervous system matures. With this in mind, the timing of disease and duration of insult can produce characteristic imaging patterns. The timing of imaging is also crucial, as typical patterns may become occult or obscure in the subacute/chronic setting. Unexplained signal abnormalities seen in the neonate may also be erroneously attributed to HIE, when in fact another underlying disease process may be the etiology. The goal after viewing this exhibit is to have a clear and concise pattern based approach for the diagnosis and prognostication of HIE while highlighting important differentials that may mimic this disease.

The exhibit will review the most common morphologic patterns of hypoxic ischemic encephalopathy in neonates with perinatal HIE using sample brain MRI and ultrasound studies from our institution over the last 3 years. Initially focus will be placed on discussing subtypes and mechanisms of classic HIE based on the severity of the insult and duration of ischemia (mild/moderate acute, mild/moderate prolonged, severe acute, and severe prolonged). Characteristic schematic and imaging examples will be provided for each category. Additionally, for each pattern of injury several alternative diagnoses will be discussed which can mimic HIE in the term neonate, and imaging examples will be provided. The potential mimics will include developmental, vascular, infectious, metabolic, and congenital etiologies.

Understanding the variable patterns of HIE is paramount in providing both an accurate report and aiding in prognostication. Equally important is knowing and considering differential diagnoses for common mimics of HIE, which may dramatically alter management.
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