**Core Concept**
Frey's syndrome is a parasympathetic nerve dysfunction resulting in sweating and flushing over the face during eating, due to aberrant regeneration of the auriculotemporal nerve. This nerve carries parasympathetic fibers from the facial nerve that normally innervate salivary glands, and when damaged during surgery, these fibers reinnervate sweat glands, causing inappropriate sweating.

**Why the Correct Answer is Right**
The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve (V3) and carries parasympathetic fibers from the facial nerve. During surgical procedures (e.g., parotidectomy), when the facial nerve is injured, these parasympathetic fibers may aberrantly reinnervate sweat glands in the skin over the cheek or temple. This leads to sweating during eating — the hallmark of Frey’s syndrome. The auriculotemporal nerve is the key pathway involved in this phenomenon.

**Why Each Wrong Option is Incorrect**
Option A: Trigeminal nerve is the main sensory nerve of the face but does not carry parasympathetic fibers responsible for the syndrome.
Option B: Mandibular division of trigeminal is the source of the auriculotemporal nerve, but it is not the nerve directly involved in Frey’s syndrome.
Option D: Lingual nerve is involved in sensory innervation of the tongue and does not carry parasympathetic fibers associated with sweating.

**Clinical Pearl / High-Yield Fact**
Frey’s syndrome is a common post-surgical complication after parotid gland surgery, especially parotidectomy. It is not due to facial nerve palsy but to **aberrant regeneration** of parasympathetic fibers, leading to **inappropriate sweating** during meals. Always consider it when there is sweating in the face after head/neck surgery.

✓ Correct Answer: C. Ariculo temporal