Cranial nerve most commonly involved in malignant otitis externa ?
**Core Concept**
Malignant otitis externa, also known as necrotizing otitis externa, is a serious infection of the external auditory canal that can lead to cranial nerve involvement due to its proximity to the cranial structures. The condition is often seen in immunocompromised individuals, such as those with diabetes mellitus or HIV/AIDS.
**Why the Correct Answer is Right**
The cranial nerve most commonly involved in malignant otitis externa is the **VII (Facial Nerve)**. This is because the facial nerve passes through the temporal bone, which is adjacent to the external auditory canal. The infection can spread to the facial nerve, causing symptoms such as facial paralysis, numbness, or weakness. The facial nerve is responsible for controlling the muscles of facial expression, taste to the anterior two-thirds of the tongue, and some motor functions of the ear.
**Why Each Wrong Option is Incorrect**
**Option A:** The **IX (Glossopharyngeal Nerve)** is not typically involved in malignant otitis externa, although it does pass through the jugular foramen, which is near the external auditory canal.
**Option B:** The **X (Vagus Nerve)** is not commonly affected by malignant otitis externa, as it has a more distant course and is not as closely related to the external auditory canal.
**Option C:** The **XI (Accessory Nerve)** is not typically involved in malignant otitis externa, although it does pass through the jugular foramen, which is near the external auditory canal.
**Clinical Pearl / High-Yield Fact**
Malignant otitis externa is a medical emergency that requires prompt treatment with antibiotics and supportive care. Early recognition and treatment can help prevent complications, such as cranial nerve involvement and facial paralysis.
**Correct Answer:** C.