A 58-year-old man with hypertension presents with acute onset right-sided weakness and right-sided sensory loss. MRI shows a lacunar infarct in the left internal capsule. Which vascular territory is most likely occluded?

Explanation

## Vascular Supply of the Internal Capsule ### Blood Supply by Artery **Key Point:** The internal capsule receives blood supply from multiple sources, but lacunar infarcts affecting the posterior limb (causing motor + sensory deficits) are classically supplied by the **lenticulostriate arteries** (also called lateral perforating branches of the MCA). ### Arterial Supply Pattern | Artery | Territory | Clinical Significance | |--------|-----------|----------------------| | **Lenticulostriate (lateral perforators from MCA)** | Posterior limb, putamen, external capsule | Most common source of lacunar infarcts; hypertension-related | | **Anterior choroidal artery** | Anterior limb, genu, choroid plexus, parts of internal capsule | Can cause motor + sensory deficits; less common for pure lacunar stroke | | **Medial lenticulostriate (ACA perforators)** | Medial putamen, medial internal capsule | Supplies medial structures | | **Posterior choroidal artery** | Posterior thalamus, choroid plexus | Does not supply internal capsule | ### Why Lenticulostriate? **High-Yield:** Lenticulostriate arteries are small penetrating vessels arising from the M1 segment of the MCA. They are particularly vulnerable to hypertensive damage (lipohyalinosis), making them the most common source of **pure motor stroke** and **motor + sensory stroke** (lacunar syndromes) affecting the internal capsule. **Clinical Pearl:** The clinical presentation of contralateral motor weakness + sensory loss in a hypertensive patient with a lacunar infarct in the posterior limb is pathognomonic for lenticulostriate occlusion. **Mnemonic:** **LACS** = **L**enticulostriate, **A**cute, **C**ontralateral motor/sensory, **S**mall (lacunar) infarct.