]> 2026-07-31T14:08:25+00:00 WBR0894 0 en Subarachnoid hemorrhage Subarachnoid hemorrhage appears as a high-attenuating, amorphous substance that fills the normally dark CSF-filled subarachnoid spaces. This is most evident in the largest subarachnoid spaces, such as the suprasellar cistern and Sylvian fissures. Acute ischemic stroke Typical changes observed after an ischemic infarct may not be evident during the early hours following onset of symptoms of stroke. Some of the subtle changes seen are loss of gray-white differentiation and swelling of the gyri that produces sulcal effacement. Acute intracerebral hemorrhage Acute hemorrhage is evident as areas of hyperdensity on CT (darker than the surrounding brain parenchyma) and areas of hypointensity on MRI. Chronic ischemic stroke This will be evident as areas of hypodensity on CT. Chronic intracerebral hemorrhage This manifests as areas of hyperdensity on CT. The image above shows loss of gray-white differentiation, one of the subtle changes appreciable very early after an infarct. Another feature of an ischemic infarct is the swelling of the gyri that produces sulcal effacement (not appreciable in this image). Non-contrast enhanced CT (NCCT) is the preferred immediate brain imaging to rule out or confirm hemorrhage in cases of suspected stroke, especially in the acute setting. Areas of hemorrhage on NCCT appear lighter (hypodensity) while areas of infarct are usually darker (hyperdense). Educational Objective: NCCT is used to rule out hemorrhage during an acute stroke. It is important to know how to differentiate a bleed from ischemic areas on a CT or MRI.<br/> '''Educational Objective:''' <br/> '''References:''' Internal medicine B Neurology 2020-10-28T02:01:00Z 2459150.5840278 WBR0894