A 52-year-old woman with chronic hypertension and diabetes mellitus presents with progressive gait ataxia, dysmetria, and nystagmus over 3 weeks. Imaging reveals a hypertensive hemorrhage in the cerebellum. Which is the most common site of primary hypertensive cerebellar hemorrhage?

Explanation

## Hypertensive Cerebellar Hemorrhage: Most Common Site **Key Point:** Hypertensive cerebellar hemorrhage most commonly occurs in the **dentate nucleus and deep cerebellar white matter** (superior cerebellar peduncle region), accounting for approximately 70–80% of primary cerebellar hemorrhages in hypertensive patients. This is distinct from ischemic cerebellar stroke, where PICA territory infarction is most common. ### Comparison: Cerebellar Hemorrhage vs. Infarction Sites | Pathology | Most Common Site | Mechanism | Artery Involved | |-----------|------------------|-----------|------------------| | **Hemorrhage (HTN)** | Dentate nucleus, deep white matter | Rupture of penetrating arteries | Branches of SCA | | **Infarction** | Inferior vermis, lateral hemisphere | Thromboembolism, atherosclerosis | PICA | **High-Yield:** Hypertensive hemorrhage preferentially affects the **deep cerebellar structures** (dentate nucleus and superior cerebellar peduncle) because these regions are supplied by small penetrating branches of the superior cerebellar artery that are vulnerable to lipohyalinosis and microaneurysm formation (Charcot-Bouchard aneurysms) in chronic hypertension. **Clinical Pearl:** Cerebellar hemorrhage is a neurosurgical emergency. Expansion of the hematoma can cause obstructive hydrocephalus (compression of the fourth ventricle) and brainstem herniation. Patients with >3 cm hematoma or signs of hydrocephalus require urgent decompression. **Mnemonic:** **"Deep HTN Bleed"** — Hypertensive cerebellar hemorrhage bleeds into the **Deep** structures (dentate nucleus, white matter), not the superficial cortex. This contrasts with hypertensive lobar hemorrhages in the cerebrum, which occur in the subcortical white matter of the lobes. ### Why Dentate Nucleus and Superior Cerebellar Peduncle? 1. **Vascular anatomy:** The dentate nucleus and surrounding white matter are supplied by penetrating branches of the SCA that are prone to lipohyalinosis in chronic hypertension. 2. **Pressure vulnerability:** These deep structures experience higher intravascular pressures from parent vessels, making them susceptible to rupture. 3. **Frequency in clinical series:** Autopsy and imaging studies consistently show this site in 70–80% of hypertensive cerebellar hemorrhages. ### Clinical Presentation Hematoma in the dentate nucleus region produces: - Ipsilateral limb ataxia and dysmetria (dentate nucleus is the output nucleus) - Nystagmus and vertigo - Dysarthria - Potential obstructive hydrocephalus if mass effect compresses the fourth ventricle [cite:Robbins 10e Ch 28]