However, within 3 hours of symptoms onset, these early ischemic changes are found only in 31-53% of the patient but improves at 6 h with sensitivity of 67% [ref6] [ref12]. Although normal CT brain might be found, it does not excludes the presence of ischemic stroke as it has a low negative predictive value (27%) in the first 6 hour [ref12].What is an ischemic stroke?
What is an Ischemic Stroke? Ischemic stroke occurs when a vessel supplying blood to the brain is obstructed. It accounts for about 87 % of all strokes. Fatty deposits lining the vessel walls, called atherosclerosis, are the main cause for ischemic stroke.How quickly do CT findings change after a stroke?
Due to the fact the ischemic stroke is a dynamic process, the CT findings change over time. The early ischemic changes can be present anytime up to 72hour regardless of the initial presence of CT findings [ref1]. Hypodensity area detected by CT previously may gradually expand, involving both gray and white matter of the brain.What is the time course of stroke on non enhanced CT?
Time course of ischemic stroke on non-enhanced CT. The ischemic changes detected by unenhanced CT are caused by cytotoxic edema (occurred within 30 minutes) attributed to lactic acidosis and failure of cellular membrane’s ion pumps. This results in redistribution of water from extracellular to intracellular space.