Frey’s syndrome is due to faulty regeneration of damaged nerve fibers. The sources of that injured nerve is
## **Core Concept**
Frey's syndrome, also known as gustatory sweating or auriculotemporal syndrome, results from aberrant regeneration of nerve fibers between remaining parasympathetic secretomotor fibers and sympathetic nerves that innervate sweat glands and blood vessels. This condition often occurs following damage to the nerves in the parotid gland area.
## **Why the Correct Answer is Right**
The correct answer involves the **auriculotemporal nerve**, a branch of the mandibular division of the trigeminal nerve (cranial nerve V). This nerve carries sympathetic fibers to the sweat glands and blood vessels of the face and parasympathetic fibers from the otic ganglion to the parotid gland. When the auriculotemporal nerve is damaged, as in parotid surgery, and then aberrantly regenerates, it can lead to Frey's syndrome. The aberrant regeneration causes muscarinic receptors (originally meant for acetylcholine released by parasympathetic fibers) to be expressed on sympathetic nerve fibers. When these fibers are stimulated, they release acetylcholine, which acts on muscarinic receptors, leading to sweating and flushing.
## **Why Each Wrong Option is Incorrect**
- **Option A:** The **greater petrosal nerve** carries parasympathetic fibers from the facial nerve to the lacrimal gland and mucous membranes of the nasal and oral cavities. It is not directly involved in the innervation of the parotid gland or the manifestation of Frey's syndrome.
- **Option B:** The **otic ganglion** is a parasympathetic ganglion involved in the pathway of the parasympathetic innervation to the parotid gland but is not the source of the injured nerve leading to Frey's syndrome.
- **Option D:** The **lingual nerve**, another branch of the mandibular division of the trigeminal nerve, provides sensory innervation to the anterior two-thirds of the tongue. While it is in the vicinity and can be involved in some nerve damage scenarios, it is not the primary nerve associated with Frey's syndrome.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that Frey's syndrome often occurs after damage to the auriculotemporal nerve, commonly as a complication of **parotid surgery**. The syndrome presents with sweating (hyperhidrosis) and flushing of the skin over the area of the parotid gland in response to stimuli that would normally cause salivation, such as the smell or taste of food.
## **Correct Answer:** C. auriculotemporal nerve.