The evolution of cerebral infarction produces time-dependent imaging changes on MRI. Recognizing these helps estimate the infarct age, guide thrombolysis/thrombectomy, and avoid misinterpretation.
🕒 Stages of Infarct & MRI Features
| Stage | Timeframe | DWI | ADC | T2/FLAIR | T1 | Other Features |
|---|---|---|---|---|---|---|
| Hyperacute | 0–6 hrs | Bright (restricted diffusion) | Low (true restriction) | Usually normal | Normal | DWI is most sensitive |
| Acute | 6 hrs – 3 days | Bright | Low | Subtle hyperintensity, sulcal effacement | Normal to hypointense | Early mass effect |
| Early Subacute | 3–7 days | Bright (may persist) | Low → pseudonormalizing by day 5–7 | Hyperintense edema | Hypointense | Gyriform enhancement (after ~3–5 days) |
| Late Subacute | 1–2 weeks | May normalize | ADC pseudonormal (appears normal despite infarct) | Hyperintense | Hypointense | More obvious enhancement, mass effect peaks |
| Chronic | > 2 weeks | Variable | High (gliosis, encephalomalacia) | Gliosis, volume loss, T2 hyperintensity | Hypointense | Ex vacuo dilatation of ventricles/sulci |
🔎 Key Teaching Points
- DWI: most sensitive → detects infarction within minutes.
- ADC: falls in acute phase (restricted diffusion), pseudonormalizes by 1–2 weeks, then increases (chronic gliosis).
- T2/FLAIR: lag behind diffusion, becoming abnormal after ~6 hours.
- Gadolinium enhancement: appears 3–5 days (luxury perfusion), peaks at 1–2 weeks, disappears by ~2–3 months.
- Chronic stage: volume loss, gliosis, CSF-like cavity, no mass effect.
