Non-contrast head CT reveals global hypoattenuation of brain parenchyma compatible with diffuse cerebral edema. There is loss of gray-white differentiation and reversal of the normal hyperdense basal ganglia and hypodense internal capsules (ROI 1 - 22 HU; ROI 2 - 29 HU). There is complete loss of sulci. The lateral ventricles are markedly effaced appearing slit-like. The basal cisterns are similary effaced concerning for early transtentorial herniation. Relative hyperdense appearance of the suprasellar cistern, intracranial vessels and tentorium mimicks subarachnoid hemorrhage. Findings are compatible with hypoxic-ischaemic brain injury in the setting of cardiac arrest.