A 72-year-old woman with a history of atrial fibrillation (not on anticoagulation) and hypertension presents with acute onset hemiplegia and headache. MRI shows a lobar hemorrhage in the parietal region with microhemorrhages on susceptibility-weighted imaging scattered throughout the cortex. What is the most common cause of lobar intracerebral hemorrhage in elderly patients?

## Most Common Cause of Lobar ICH in Elderly Patients **Key Point:** Cerebral amyloid angiopathy (CAA) is the **most common cause of lobar (cortical) intracerebral hemorrhage in elderly patients**, whereas hypertension preferentially causes deep (basal ganglia, thalamic, pontine) hemorrhages. ### Differential Diagnosis: Lobar vs. Deep ICH by Cause | Cause | Most Common Location | Patient Population | Pathophysiology | |-------|----------------------|-------------------|------------------| | **Cerebral amyloid angiopathy** | **Lobar (cortical)** | **Elderly (>70 years)** | Amyloid-β deposition in cortical vessel walls → fragility | | Hypertension | Deep (basal ganglia, thalamus, pons) | Middle-aged to elderly | Lipohyalinosis of penetrating arteries | | Anticoagulation | Any location (lobar or deep) | Any age on anticoagulants | Therapeutic or supratherapeutic INR | | AVM/Aneurysm | Variable (often lobar) | Younger patients | Structural vascular malformation | | Amyloid-related imaging abnormalities (ARIA) | Lobar | Patients on anti-amyloid monoclonal antibodies | Amyloid clearance-related inflammation | ### Cerebral Amyloid Angiopathy: Key Features **High-Yield:** CAA is characterized by: 1. **Amyloid-β deposition** in the walls of cortical and leptomeningeal vessels 2. **Lobar hemorrhages** (parietal, temporal, occipital > frontal) 3. **Recurrent hemorrhages** — high risk of rebleeding (up to 10% per year) 4. **Microhemorrhages** on susceptibility-weighted imaging (SWI) or gradient-recalled echo (GRE) sequences 5. **Cortical superficial siderosis** (hemosiderin in cortical layers) 6. **No hypertension required** — occurs in normotensive elderly **Mnemonic: CHANT** — **C**ortical location, **H**ypertension-independent, **A**myloid deposition, **N**o deep bleeds, **T**herapy-resistant (high rebleeding risk) ### Clinical Pearl **Clinical Pearl:** The presence of **multiple microhemorrhages on SWI/GRE** in a lobar distribution in an elderly patient is pathognomonic for CAA. The patient in this case has scattered cortical microhemorrhages, which strongly suggests CAA rather than hypertensive ICH (which would show a single deep hemorrhage without microhemorrhages). ### Boston Criteria for CAA Diagnosis **Key Point:** The Boston Criteria (modified) classify CAA as: - **Definite CAA:** Pathological confirmation of amyloid-β in vessel walls - **Probable CAA:** Clinical + MRI evidence (lobar ICH + microhemorrhages + age >55 years, no other cause) - **Possible CAA:** Lobar ICH + age >55 years ### Why CAA Causes Lobar Hemorrhage Amyloid-β deposition weakens the walls of cortical arterioles and capillaries, making them prone to rupture. Unlike hypertensive lipohyalinosis (which affects deep penetrating arteries), CAA selectively affects superficial cortical vessels. ### Management Implications **Warning:** Patients with CAA-related ICH should **avoid anticoagulation** and **antiplatelet agents** when possible, as they significantly increase rebleeding risk. Strict blood pressure control is essential. [cite:Harrison 21e Ch 296; Robbins 10e Ch 28]