A 75-year-old woman, associated with emboli and presents with severe pain in the ear as if bathed in acid. In this case, the likely lesion is at
First, the key symptoms here are emboli and ear pain. Emboli can be from a clot that's traveled from another part of the body, often the heart or aorta. The ear pain is intense and burning. This makes me think of the distribution of nerves in the ear. The ear is innervated by several nerves, but the main ones are the auriculotemporal nerve (from the trigeminal), the lesser occipital nerve (from the cervical plexus), and the great auricular nerve (from the cervical plexus).
The description of the pain as "acid bath" might suggest a superficial burn or irritation, but since it's associated with an embolus, it's more likely a vascular issue. An embolus in a blood vessel supplying the ear could lead to ischemia, causing pain. The auriculotemporal nerve is closely related to the superficial temporal artery, which branches from the external carotid artery. If there's an embolus in the carotid artery, it could affect the superficial temporal artery, leading to infarction and subsequent pain.
The auriculotemporal nerve is responsible for sensory innervation of the external ear, including the tragus and the skin over the temporomandibular joint. Damage here would cause pain in that area. The other nerves like the lesser occipital and great auricular nerves are more posterior, so an embolus affecting them might present with different pain locations. The vagus nerve's auricular branch (Arnold's nerve) can cause referred pain, but that's more related to the throat and pharynx, not the external ear.
So the lesion is likely in the auriculotemporal nerve due to embolic occlusion of the superficial temporal artery. The other options (lesser occipital, great auricular, vagus) don't fit the anterior ear pain described. The clinical pearl here is to remember the vascular supply and nerve distribution of the ear, especially in the context of emboli from carotid sources.
**Core Concept**
This question tests knowledge of the **auriculotemporal nerve's** role in ear pain and its vascular supply. Embolic infarction of the superficial temporal artery (a branch of the external carotid artery) can cause ischemia in the auriculotemporal nerve territory, leading to severe burning pain.
**Why the Correct Answer is Right**
The **auriculotemporal nerve** (a branch of the trigeminal nerve, CN V3) innervates the **external auditory meatus, tragus, and temporoparietal skin**. An embolus in the superficial temporal artery (which runs alongside the auriculotemporal nerve) would cause ischemic injury, resulting in the described "acid bath" pain. This nerve is closely associated with the external carotid artery system, making it vulnerable to emboli from carotid sources.
**Why Each Wrong Option is Incorrect**
**Option A:** The *lesser occipital nerve* (C2) supplies the posterior scalp and upper