## Clinical Presentation Analysis The patient presents with acute focal neurological deficit (right hemiparesis and expressive aphasia) localized to the left MCA territory, consistent with acute ischemic stroke. ## MRI DWI/ADC Interpretation **Key Point:** DWI hyperintensity with corresponding ADC hypointensity is the hallmark of acute ischemic stroke and represents **cytotoxic edema**. In acute ischemia: 1. Ischemic tissue undergoes energy failure 2. Na⁺/K⁺-ATPase pump fails → Na⁺ and water accumulate intracellularly 3. Water shifts from extracellular to intracellular space (cytotoxic edema) 4. Restricted water diffusion → **DWI hyperintensity** and **ADC hypointensity** ## Timeline Correlation | Imaging Modality | Timeline | Findings | |---|---|---| | **Non-contrast CT** | 0–24 hours | Normal (excludes hemorrhage) | | **DWI/ADC MRI** | Minutes to hours | Hyperintense DWI + hypointense ADC | | **Conventional MRI (T2/FLAIR)** | 6–12 hours | T2/FLAIR hyperintensity appears | | **CT perfusion** | Early | Perfusion deficit | **High-Yield:** DWI is the most sensitive imaging modality for acute ischemic stroke, detecting infarction within **minutes** of symptom onset, whereas conventional CT/MRI may appear normal in the first 6–12 hours. ## Why This Patient Qualifies for Thrombolysis - Symptom onset to imaging: 3 hours (within 4.5-hour IV thrombolysis window) - No hemorrhage on NCCT - Acute DWI lesion confirms ischemia - Candidate for IV alteplase or mechanical thrombectomy **Clinical Pearl:** The combination of acute clinical stroke syndrome + DWI positivity on MRI is diagnostic of acute ischemic stroke, even if conventional MRI (T2/FLAIR) appears normal. 
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