Purpose or Case Report: Hypoxic ischemic encephalopathy (HIE) is a significant cause of severe long term neurological impairment and mortality in the newborn. It develops in two stages; the ischemic phase caused by hypoxia leading to cytotoxic edema, followed by the reperfusion phase with the release of reactive oxygen species leading to oxidative damage and vasogenic edema. Imaging plays a key role in diagnosis, management, and treatment of HIE. It also offers important prognostic information. MRI remains the preferred imaging modality.
Microvascular imaging (MVI) is a novel advanced Doppler ultrasound (US) technique that permits visualization of the microvasculature without the administration of contrast agents. It enhances the visualization of flow signal in the microvessels and helps reveal functional insights into the brain at high resolution.

A female newborn of 32 weeks of gestation was delivered by urgent C-section following absent fetal movements and suspected placental abruption. She was born to a mother with a reported exposure to cocaine with a last use the week prior to delivery. At birth, no pulse was detected, and CPR was initiated immediately. O2 saturation remained low during resuscitation despite intubation and a FiO2 of 100%. Return of spontaneous circulation was noted 50 minutes after birth. Following birth, the patient was diagnosed with severe HIE and had multiple seizures. Her physical exam revealed fixed and cloudy pupils with a diameter of 4 mm and no brainstem reflexes. At one day of life, a brain US was done and displayed diffusely increased echogenicity of the parenchyma and crowding of the cortical gyri concerning for cerebral edema. MVI revealed markedly increased microvascular perfusion in the basal ganglia, thalami, and periventricular region consistent with post-ischemic reperfusion in the setting of HIE. MRI showed diffusion restriction throughout the brain including the medial temporal lobes, hippocampi, thalami, basal ganglia, and frontoparietal cortex. Also noted was extensive hyperintense signal abnormality on T2-weighted sequences within both the gray and white matter with loss of the gray-white matter differentiation and moderate sulcal effacement. These findings confirmed the diagnosis of severe HIE.

In our case, MVI demonstrated marked hyperperfusion in the basal ganglia, thalami and periventricular region. Whether this MVI flow signature can prognosticate poor clinical outcomes, it warrants further investigation.
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