**Question:** Following Caldwell Luc operation, a patient develops hypoesthesia. Which nerve is damaged?

**Core Concept:** The Caldwell Luc operation is a surgical procedure used to relieve obstructive sleep apnoea by removing or loosening the soft tissues in the airway to improve ventilation. Hypoesthesia refers to a reduced ability to feel touch, temperature, or pressure. The main nerves involved in sensory function are the sensory branches of the cranial nerves.

**Why the Correct Answer is Right:** In the Caldwell Luc operation, the surgeon targets and potentially damages the hypoglossal nerve, specifically its sensory branch. The hypoglossal nerve (CN XII) is responsible for the movement of the tongue and is responsible for the sensory function in the tongue and floor of the mouth. Damage to this nerve can lead to hypoesthesia in these areas, as seen in the presented question.

**Why Each Wrong Option is Incorrect:**

A. Cranial Nerve X (Vasocongestive Nerve): This option refers to the vasomotor nerve, which controls blood flow and does not correspond to the sensory function being affected in the question.
B. Cranial Nerve XI (Accessory Nerve): The accessory nerve controls neck muscles (not relevant to the tongue and oral cavity) and does not affect sensory function.
C. Cranial Nerve IX (Tongue Nerve): This option refers to the glossopharyngeal nerve (CN IX), which controls taste, not sensory function. It is also responsible for motor function in the pharynx and tonsil, not relevant to the oral cavity.
D. Cranial Nerve XII (Hypoglossal Nerve): As mentioned above, this nerve controls tongue movement and is responsible for sensory function in the tongue and floor of the mouth, thus making it the correct answer.

**Clinical Pearl:** Hypoesthesia following the Caldwell Luc operation is a result of the surgical manipulation and potential damage to the hypoglossal nerve (CN XII). Understanding the role of different cranial nerves is essential in interpreting the clinical findings and choosing the correct diagnosis and treatment plan for patients with neurological symptoms post-surgery or trauma.