Unenhanced CT and acute stroke physiology.

Unenhanced CT remains the most widely used imaging technique and is the standard of care for acute stroke evaluation. Early ischemic signs (EIS) within the first 3 to 6 hours of symptom onset (eg, parenchymal hypodensity, sulcal effacement, and dense vessel) have been advocated as a triage tool for thrombolytic therapy. Recent studies have challenged the relevance of these EIS within 3 hours of stroke onset, with advanced MR and CT methods increasingly competing with unenhanced CT as the primary imaging modality for acute ischemia. Nonetheless, the insights regarding acute stroke physiology provided by studying the CT evolution of early ischemic signs continue to be valuable for the informed interpretation of all stroke images. It is these insights that comprise the topic of this article.