A 58-year-old man from Delhi presents with acute-onset left hemiparesis and speech difficulty. MRI brain with DWI/PWI is performed within 4 hours of symptom onset. Regarding the expected imaging findings and their interpretation in acute ischemic stroke, all of the following are correct EXCEPT:

Question

Accepted Answer

C. Apparent diffusion coefficient (ADC) maps will show hyperintensity in areas of acute ischemia, confirming true restriction of water diffusion. ## DWI/PWI Interpretation and ADC Maps in Acute Stroke

**Key Point:** ADC maps are HYPERINTENSE (bright) in areas of **chronic** infarction or vasogenic edema, but are **HYPOINTENSE (dark)** in acute ischemia due to cytotoxic edema. This is a common source of confusion.

### Why Option C (Correct Answer) is Wrong

In acute ischemia, **ADC is LOW (hypointense/dark)**, not hyperintense. This reflects restricted water diffusion due to cytotoxic edema. The DWI signal is HIGH (hyperintense) because of T2 shine-through combined with restricted diffusion. ADC hypointensity confirms that the DWI signal is due to true restriction, not T2 prolongation alone.

**High-Yield:** Remember the **DWI/ADC mismatch** in acute stroke:
- **DWI hyperintense + ADC hypointense** = acute ischemia (cytotoxic edema)
- **DWI hyperintense + ADC hyperintense** = chronic infarction or vasogenic edema (T2 shine-through)

### Why the Other Options are Correct

| Option | Validity |
|--------|----------|
| **Option A** | Correct. Small DWI lesion with normal PWI = completed infarction; no penumbra to salvage. |
| **Option B** | Correct. Large DWI/PWI mismatch = substantial penumbra; patient eligible for reperfusion therapy even beyond standard 4.5-hour window (up to 24 hours with favorable imaging). |
| **Option D** | Correct. SWI is sensitive for detecting intravascular thrombus (hypointense signal) and microhemorrhages; useful for confirming vessel occlusion. |

**Clinical Pearl:** The **DWI/PWI mismatch** is the imaging biomarker for the ischemic penumbra and guides patient selection for extended-window thrombolysis or thrombectomy (up to 24 hours in selected cases).

**Mnemonic — ADC in Acute vs. Chronic Ischemia:**
- **A**cute: ADC **A**ppears **D**ark (hypointense)
- **C**hronic: ADC **C**lear/bright (hyperintense)

```mermaid
flowchart TD
  A[Acute Ischemic Stroke]:::outcome --> B{DWI/ADC Pattern}:::decision
  B -->|DWI high + ADC low| C[Acute ischemia with cytotoxic edema]:::action
  B -->|DWI high + ADC high| D[Chronic infarction or vasogenic edema]:::outcome
  C --> E{DWI/PWI Mismatch?}:::decision
  E -->|Yes, large mismatch| F[Penumbra present - eligible for late reperfusion]:::action
  E -->|No or small mismatch| G[Completed infarction - no salvageable tissue]:::outcome
```

Answer

A. Susceptibility-weighted imaging (SWI) may reveal a hypointense dot or line representing thrombus within a cerebral vessel, aiding in vessel occlusion diagnosis

Answer

B. If DWI shows a small acute infarct but PWI demonstrates a much larger area of hypoperfusion, the patient is a candidate for late-window thrombectomy or thrombolysis

Answer

D. A DWI lesion restricted to the gray matter of the insular cortex with normal PWI suggests completed infarction in a small penetrating artery territory

A 58-year-old man from Delhi presents with acute-onset left hemiparesis and speech difficulty. MRI brain with DWI/PWI is performed within 4 hours of symptom onset. Regarding the expected imaging findings and their interpretation in acute ischemic stroke, all of the following are correct EXCEPT:

Explanation

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