## Imaging Features of Intracerebral Hemorrhage ### CT Findings in Acute ICH **Key Point:** Non-contrast CT is the gold standard for detecting acute ICH. Hyperdensity (>60 HU) represents acute blood (oxyhemoglobin). Surrounding hypodensity indicates cerebral edema. ### The Blend Sign **High-Yield:** The "blend sign" (also called "heterogeneous density sign") refers to: - Heterogeneous appearance of the hematoma with areas of **lower attenuation interspersed within high-density blood** - Indicates **active extravasation** of blood at the time of imaging - Associated with **hematoma expansion** (risk of poor outcome) - Predicts need for aggressive hemostasis and monitoring **Clinical Pearl:** Presence of blend sign warrants closer monitoring and consideration of hemostasis strategies (e.g., reversal of anticoagulation, BP control). ### Microhemorrhages and CAA **High-Yield:** Cerebral amyloid angiopathy (CAA) is a leading cause of lobar ICH in elderly patients. Imaging features: - **SWI and gradient-echo (GRE) MRI** are highly sensitive for detecting microhemorrhages - **Multiple microhemorrhages in a lobar distribution** (cortical and subcortical) are highly specific for CAA - Microhemorrhages appear as small foci of hypointensity (blooming artifact) - Boston Criteria use microhemorrhage pattern to support CAA diagnosis ### Hypertensive ICH **Key Point:** Hypertensive hemorrhage occurs in characteristic locations due to rupture of **Charcot-Bouchard aneurysms** (lipohyalinosis of small penetrating arteries): - **Basal ganglia** (putamen/globus pallidus) — 50–60% of cases - **Thalamus** — 15–25% - **Pons** (brainstem) — 5–10% - **Cerebellum** — 5–10% - **Lobar (subcortical white matter)** — less common in pure hypertension **Mnemonic:** **BTP-C** = Basal ganglia, Thalamus, Pons, Cerebellum (hypertensive ICH locations) ### The "Black Hole Sign" — The False Statement **Warning:** The "black hole sign" does **NOT** represent hemoglobin oxidation or indicate a chronic hematoma of >3 weeks. **Correct Definition:** The "black hole sign" (or "blooming artifact") refers to: - **Hypointensity on T2/GRE sequences** caused by **susceptibility artifact from deoxyhemoglobin or hemosiderin** - Seen in **subacute to chronic phases** of ICH (days to weeks onward) - Represents **iron deposition** from hemoglobin breakdown, not oxidation per se - Does NOT specifically indicate >3 weeks; can appear earlier depending on sequence and field strength **Clinical Pearl:** The evolution of ICH on MRI follows hemoglobin metabolism: - **Hyperacute (0–6 hours):** Oxyhemoglobin (isointense T1, hyperintense T2) - **Acute (6 hours–3 days):** Deoxyhemoglobin (hypointense T2, blooming on GRE) - **Early subacute (3–7 days):** Methemoglobin (hyperintense T1 and T2) - **Late subacute (1–4 weeks):** Methemoglobin + hemosiderin rim (hyperintense T1, hypointense T2 rim) - **Chronic (>4 weeks):** Hemosiderin (hypointense T2, blooming on GRE) The timeline is variable and depends on hematoma size, location, and imaging sequence. ### Summary Table: ICH Imaging Features | Feature | Finding | Significance | | --- | --- | --- | | Blend sign | Heterogeneous density on CT | Active bleeding, hematoma expansion risk | | Microhemorrhages (SWI) | Multiple lobar foci of hypointensity | CAA diagnosis support | | Hypertensive ICH location | Basal ganglia, thalamus, pons, cerebellum | Charcot-Bouchard rupture | | Black hole sign | Hypointensity on T2/GRE | Subacute-chronic phase, NOT specific to >3 weeks | [cite:Harrison 21e Ch 296] ## Why the Correct Answer Is Correct Option 3 is **FALSE** because the "black hole sign" does not specifically indicate a hematoma of >3 weeks duration. It represents susceptibility artifact from deoxyhemoglobin or hemosiderin and can appear earlier. The timeline of ICH evolution on MRI is variable and not rigidly fixed at >3 weeks.
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