A 72-year-old woman on anticoagulation for atrial fibrillation presents with acute neurological deficit. MRI brain with susceptibility-weighted imaging (SWI) is performed. Regarding the MRI sequences and imaging findings in acute hemorrhagic stroke, all of the following statements are correct EXCEPT:

Explanation

## MRI Sequences in Hemorrhagic Stroke **Key Point:** T1-weighted imaging with gadolinium enhancement is NOT reliable for distinguishing acute from chronic hemorrhage. The distinction is based on the intrinsic T1 and T2 signal characteristics of hemoglobin oxidation state, not enhancement patterns. ### Correct MRI Sequence Applications | Sequence | Use in Hemorrhage | Key Features | |----------|-------------------|---------------| | **SWI / Gradient-Echo** | Microhemorrhages, hemosiderin | Highly sensitive; shows blooming artifact | | **DWI** | Acute ischemia (NOT acute ICH) | Restricted diffusion in ischemia; normal in pure hemorrhage | | **FLAIR** | SAH detection (superior to T2) | Suppresses CSF; shows blood as hyperintense | | **T1-weighted (pre-gadolinium)** | Acute → subacute hemorrhage dating | Intrinsic hyperintensity from methemoglobin | | **T2-weighted** | Chronic hemorrhage (hemosiderin) | Hypointensity from iron deposition | **High-Yield:** Gadolinium enhancement does NOT reliably distinguish acute from chronic hemorrhage. Enhancement can occur in both due to blood-brain barrier disruption (acute) or associated lesions (chronic). ### Hemorrhage Evolution on MRI ```mermaid flowchart TD A["Acute Hemorrhage<br/>(0-3 days)"]:::outcome --> B["Deoxyhemoglobin<br/>T2: Hypointense<br/>T1: Isointense"]:::outcome B --> C["Early Subacute<br/>(3-7 days)"]:::outcome C --> D["Methemoglobin<br/>T1: Hyperintense<br/>T2: Hyperintense"]:::outcome D --> E["Late Subacute<br/>(1-2 weeks)"]:::outcome E --> F["Chronic<br/>Hemosiderin rim<br/>T2: Hypointense"]:::outcome F --> G["SWI: Blooming<br/>artifact persists"]:::outcome ``` **Clinical Pearl:** The distinction between acute and chronic hemorrhage relies on the paramagnetic properties of hemoglobin and its breakdown products (deoxyhemoglobin → methemoglobin → hemosiderin), NOT on gadolinium enhancement patterns. ### Why Gadolinium Enhancement Is Unreliable 1. **Acute hemorrhage:** BBB disruption may allow gadolinium leakage → enhancement 2. **Chronic hemorrhage:** Associated gliosis, neovascularization, or underlying lesions (tumor, AVM) may enhance 3. **No pathognomonic pattern:** Enhancement does not distinguish age of bleed **Mnemonic:** **SHEC** = Sequences for Hemorrhage Evaluation: **S**WI (microhemorrhages), **H**emoglobin evolution (T1/T2 signal), **E**cho-gradient (blooming), **C**hronicity (hemosiderin on T2). [cite:Harrison 21e Ch 435; Robbins 10e Ch 28]