A 52-year-old woman from Bangalore presents 6 hours after acute onset of right hemiparesis and aphasia. Non-contrast CT head shows no hemorrhage. MRI brain with DWI sequences shows acute restricted diffusion in the left middle cerebral artery (MCA) territory. Perfusion imaging shows a larger area of hypoperfusion extending beyond the DWI lesion. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient is **beyond the 4.5-hour IV thrombolysis window** (6 hours from onset) but has imaging evidence of an acute ischemic stroke with a **mismatch pattern**: restricted diffusion (DWI lesion) smaller than the perfusion deficit (PWI lesion). This mismatch indicates salvageable tissue (penumbra). ## Imaging Interpretation **Key Point:** DWI/PWI mismatch represents the ischemic penumbra—tissue that is hypoperfused but not yet infarcted. This is the target for mechanical thrombectomy in the extended window. **High-Yield:** The presence of a significant perfusion-diffusion mismatch extends the window for mechanical thrombectomy beyond the IV thrombolysis window (up to 24 hours in selected cases with appropriate imaging criteria). ## Why Mechanical Thrombectomy is Correct - Patient is beyond IV thrombolysis window (6 hours > 4.5 hours) - DWI/PWI mismatch indicates salvageable penumbral tissue - Large vessel occlusion (MCA territory) is ideal for thrombectomy - Mechanical thrombectomy has strong evidence for extended window treatment - CTA is typically done as part of thrombectomy planning but should not delay the decision ## Comparison: IV Thrombolysis vs. Mechanical Thrombectomy | Feature | IV Thrombolysis | Mechanical Thrombectomy | |---------|-----------------|------------------------| | Time window | 0–4.5 hours (standard) | 0–24 hours (with mismatch) | | Vessel occlusion required | No | Yes (large vessel) | | DWI/PWI mismatch | Not required | Highly beneficial | | Efficacy in proximal occlusions | Lower | Higher | | Contraindications | Multiple | Fewer | | Imaging requirement | Non-contrast CT | CTA/MRA or CTP | ## Management Decision Tree ```mermaid flowchart TD A[Acute ischemic stroke]:::outcome --> B{Time since onset?}:::decision B -->|< 4.5 hours| C[IV thrombolysis eligible?]:::decision B -->|4.5-24 hours| D[Imaging mismatch present?]:::decision C -->|Yes| E[Administer IV alteplase]:::action C -->|No| F[Consider mechanical thrombectomy]:::action D -->|Yes - DWI/PWI mismatch| G[Mechanical thrombectomy]:::action D -->|No mismatch| H[Medical management]:::action E --> I[Monitor for reperfusion]:::outcome F --> J[Obtain CTA/MRA for LVO]:::action G --> J J --> K[Endovascular intervention]:::action K --> L[Successful reperfusion?]:::outcome ``` **Clinical Pearl:** The mismatch pattern (DWI < PWI) is the imaging hallmark of the ischemic penumbra and justifies mechanical thrombectomy even in the extended window.