**Question:** Jaw tightness in proximal temporal arteries. Diagnosis-

A. Arteritis
B. Carotid body tumor
C. Aneurysm
D. Arterial dissection

**Core Concept:**
Temporal artery is a terminal branch of the external carotid artery, supplying the temporal region and the muscles of mastication. Temporal artery is a thin-walled artery with a pulsatile mass when palpated. Temporal artery involvement in diseases is important in the differential diagnosis of jaw tightness or pain.

**Why the Correct Answer is Right:**
The correct answer is D) Arterial dissection. Jaw tightness in proximal temporal arteries can be due to arterial dissection, which is a separation of the inner lining (intima) from the outer lining (media) of the arterial wall. This separation creates a false lumen, leading to increased blood flow and pulsatile swelling in the affected artery.

**Why Each Wrong Option is Incorrect:**
A) Arteritis (Giant Cell Arteritis) refers to inflammation of the arterial wall, which results in pain, redness, and a non-pulsatile mass. It typically involves the temporal artery but is usually associated with other systemic symptoms like fever, weight loss, and malaise.

B) Carotid body tumor (CBT) is a benign tumor arising from the carotid body, which is located in the carotid bifurcation. Jaw tightness or pain related to CBT is not typically due to arterial involvement but rather due to compression or infiltration of surrounding structures.

C) Aneurysm is a dilatation of the arterial wall, causing a pulsatile mass. Unlike dissection, aneurysms do not cause jaw tightness or pain but rather a pulsatile mass palpable on examination.

**Clinical Pearl:**
Temporal artery involvement in diseases should prompt a thorough examination for palpable pulsatile mass or swelling. However, jaw tightness or pain can also be indicative of arterial dissection, particularly when associated with a pulsatile mass. A thorough history and examination are essential to differentiate between different causes of temporal artery involvement.