In facial nerve injury, loss of lacrimation is due to involvement of
**Core Concept**
The facial nerve (cranial nerve VII) is a complex nerve responsible for controlling facial expressions, taste, and other functions including lacrimation (tear production). The nerve has a complex course through the temporal bone, with multiple branches that innervate different structures. In facial nerve injury, the type and extent of damage can vary, leading to different clinical manifestations.
**Why the Correct Answer is Right**
Lacrimation is primarily controlled by the greater superficial petrosal nerve (GSPN), a branch of the facial nerve. The GSPN synapses in the pterygopalatine ganglion and then releases neurotransmitters to stimulate the lacrimal gland to produce tears. In cases of facial nerve injury, damage to the GSPN can disrupt this pathway, leading to loss of lacrimation. This occurs due to the loss of parasympathetic innervation to the lacrimal gland.
**Why Each Wrong Option is Incorrect**
* **Option A:** The chorda tympani nerve, another branch of the facial nerve, is responsible for taste sensation from the anterior two-thirds of the tongue. Damage to this nerve would not affect lacrimation.
* **Option B:** The zygomatic nerve, a branch of the facial nerve, provides sensory innervation to the skin of the cheek and is not involved in lacrimation.
* **Option D:** The buccal branch of the facial nerve, responsible for motor innervation to the muscles of facial expression, is not directly involved in lacrimation.
**Clinical Pearl / High-Yield Fact**
In facial nerve injuries, the order of recovery is generally as follows: taste (chorda tympani), facial expression (buccal branch), and finally lacrimation (greater superficial petrosal nerve). This sequence can be remembered using the mnemonic "Taste, then Face, then Tears".
**Correct Answer:** C.