## Distinguishing Hypertensive ICH from SAH ### Key Anatomical Difference **Key Point:** The location of bleeding is the most reliable discriminator between hypertensive ICH and SAH. Hypertensive ICH characteristically occurs in deep brain structures supplied by small penetrating arteries, while SAH occurs in the subarachnoid space around large vessels. ### Comparison Table | Feature | Hypertensive ICH | SAH | |---------|------------------|-----| | **Primary location** | Basal ganglia (50%), thalamus (15%), pons (10%), cerebellum (10%) | Subarachnoid space around major vessels (Circle of Willis) | | **Cause** | Chronic hypertension → lipohyalinosis of penetrating arteries | Ruptured aneurysm (80%), AVM, trauma | | **Headache onset** | Sudden but progressive over minutes to hours | Thunderclap (maximal at onset) | | **Neck stiffness** | Absent unless large bleed with IVH | Present (meningeal irritation) | | **CT appearance** | Intraparenchymal hematoma ± IVH | Blood in sulci, basal cisterns, sylvian fissure | ### Clinical Pearl **Clinical Pearl:** The "deep brain" location (basal ganglia, thalamus, brainstem, cerebellum) in hypertensive ICH is pathognomonic. These are supplied by small penetrating arteries that undergo lipohyalinosis from chronic hypertension. In contrast, SAH blood layers the brain surface and fills the basal cisterns because it originates from large vessels in the Circle of Willis. ### Why Location Matters **High-Yield:** The depth and distribution of hemorrhage on CT is the single most discriminating feature: - **Hypertensive ICH** → deep parenchymal hematoma (basal ganglia most common) - **SAH** → blood in subarachnoid space (visible in sulci, cisterns, fissures) This distinction is crucial because it guides management: hypertensive ICH may require surgical evacuation if large; SAH requires aneurysm imaging and vasospasm prophylaxis. [cite:Harrison 21e Ch 297]
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