**Question:** A 56 year old hypertensive patient is brought to the emergency department due to left sided hemiplegia. Hemiplegia is most commonly due to occlusion of?

A. Carotid artery
B. Vertebral artery
C. Pons
D. Basilar artery

**Core Concept:** Hemiplegia refers to the loss of muscle function in one side of the body, typically resulting from a stroke or transient ischemic attack (TIA). Hemiplegia can be caused by various conditions, but in this scenario, we are focusing on the most common cause.

**Why the Correct Answer is Right:** Hemiplegia in a hypertensive patient is most commonly due to occlusion of the internal carotid artery. This artery supplies blood to the brain and is responsible for the blood flow to the frontal lobe, which controls motor function. In this case, the occlusion leads to decreased blood flow to the left side of the brain, causing hemiplegia on the opposite side of the body.

**Why Each Wrong Option is Incorrect:**

A. Carotid artery: Although the carotid artery is involved in supplying blood to the brain, the correct answer is the internal carotid artery as it has a higher likelihood of causing hemiplegia due to its role in supplying blood to the frontal lobe.

B. Vertebral artery: The vertebral artery supplies blood to the posterior circulation of the brain, which is less likely to cause hemiplegia due to its less direct connection with the motor cortex.

C. Pons: The pons is a small region in the medulla oblongata, which is involved in controlling vital functions like breathing and cardiac function, rather than motor function.

D. Basilar artery: The basilar artery supplies blood to the brainstem and cerebellum, which is less likely to cause hemiplegia compared to the internal carotid artery, as it is less directly connected to the motor cortex responsible for motor function.

**Clinical Pearl:** Assessing the risk factors, clinical presentation, and anatomic connections can help differentiate between stroke and transient ischemic attack (TIA) etiologies. In this case, the patient's age, hypertension, and presentation of left sided hemiplegia suggest a stroke, specifically an internal carotid artery occlusion.