A 72-year-old woman with no significant past medical history presents with acute onset headache and confusion. CT head shows a hyperdense lesion in the lobar region (frontal lobe). Which is the most common cause of lobar intracerebral hemorrhage in an elderly patient without hypertension?

Explanation

## Most Common Cause of Lobar ICH in Elderly Patients **Key Point:** Cerebral amyloid angiopathy (CAA) is the most common cause of lobar intracerebral hemorrhage in elderly patients without a history of hypertension. ### Etiology of Lobar ICH | Cause | Patient Profile | Frequency | Imaging Features | |-------|-----------------|-----------|------------------| | **Cerebral amyloid angiopathy (CAA)** | **Elderly (>60 years), normotensive** | **50–60%** | Multiple lobar hemorrhages, cortical/subcortical location, microhemorrhages on SWI/GRE | | Hypertensive ICH | Middle-aged, hypertensive | 30–40% | Deep/basal ganglia location (putamen, thalamus) | | Arteriovenous malformation | Any age, can be normotensive | 5–10% | Nidus visible, enlarged draining veins, prior hemorrhage history | | Anticoagulation-related | Elderly on warfarin/DOACs | 5–10% | Any location, INR elevation (if warfarin), recent initiation | **High-Yield:** **Cerebral amyloid angiopathy** accounts for approximately **50–60%** of lobar ICH in elderly patients without hypertension. It is the leading cause of intracerebral hemorrhage in patients over 60 years of age. ### Pathophysiology of CAA 1. Accumulation of amyloid-β protein in small and medium-sized cortical and leptomeningeal vessels 2. Weakening of the vessel wall (loss of smooth muscle cells) 3. Rupture of affected vessels → lobar hemorrhage 4. Recurrent hemorrhages common (annual recurrence risk ~4%) **Clinical Pearl:** CAA-related ICH typically occurs in the **lobar distribution** (frontal, parietal, temporal, occipital lobes), sparing the deep structures. This contrasts sharply with hypertensive ICH, which favors the putamen, thalamus, pons, and cerebellum. ### Imaging Characteristics of CAA **CT Findings:** - Lobar hyperdense lesion (acute hemorrhage) - Cortical/subcortical location - Often multiple hemorrhages (recurrent bleeds) - Minimal or absent hypertension-related deep ICH **MRI Findings:** - **Susceptibility-weighted imaging (SWI)** or **gradient-recalled echo (GRE):** Multiple microhemorrhages ("microbleeds") - T1 hyperintensity in acute/subacute phase - Hemosiderin rim in chronic phase - Cortical superficial siderosis (linear hemosiderin deposition on cortical surface) **Mnemonic:** **CAA-OLD** — Cortical/lobar location, Amyloid-β deposition, Amyloid angiopathy, Older patients (>60 years), Lobar distribution, Dementia risk. ### Diagnostic Criteria for CAA (Modified Boston Criteria) **Definite CAA:** Pathological evidence of amyloid angiopathy (biopsy/autopsy) **Probable CAA:** Lobar ICH + microhemorrhages on MRI + age >55 years + absence of other cause **Possible CAA:** Lobar ICH + age >55 years + no microhemorrhages **Warning:** Do not assume all lobar hemorrhages in elderly patients are due to CAA. Always rule out secondary causes (AVM, tumor, coagulopathy, anticoagulation) before attributing to CAA.