## Early Ischemic Changes on CT and Prognostic Significance ### CT Findings in Acute Stroke **Key Point:** Hypodensity involving >1/3 of the MCA territory on early CT indicates a large infarct volume with irreversible tissue damage and is associated with poor clinical outcomes, including increased mortality and severe disability. ### Early Ischemic Change Grading | Finding | Timing | Extent | Prognosis | Clinical Significance | |---------|--------|--------|-----------|------------------------| | Loss of gray-white differentiation | 6–12 hrs | Subtle, focal | Variable | Early sign, not always irreversible | | Hypodensity <1/3 MCA territory | 6–12 hrs | Limited | Better | Smaller infarct, better recovery potential | | **Hypodensity >1/3 MCA territory** | **6–12 hrs** | **Large** | **Poor** | **Irreversible, high mortality** | | Hypodensity with mass effect | 12–24 hrs | Large | Poor | Malignant edema, herniation risk | ### Why >1/3 MCA Territory Hypodensity is Prognostically Significant 1. **Large infarct volume:** Indicates extensive irreversible tissue necrosis affecting major vascular territory. 2. **Contraindication to thrombolysis:** Patients with >1/3 MCA territory involvement are at high risk for hemorrhagic transformation and are often excluded from IV thrombolysis. 3. **Malignant MCA stroke:** Large MCA infarcts (>50% territory) carry 50–80% mortality risk due to cerebral edema and herniation. 4. **Poor functional recovery:** Extensive infarction correlates with severe disability (modified Rankin Scale 4–5). **Clinical Pearl:** The ECASS III trial and subsequent guidelines recommend against IV thrombolysis in patients with >1/3 MCA territory involvement on baseline CT due to increased hemorrhagic transformation risk. **High-Yield:** Hypodensity >1/3 MCA territory = large infarct = poor prognosis = contraindication to thrombolysis. This is tested frequently in NEET PG. 
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