Damage to facial nerve just above branching of chorda tympani causes all except:
**Core Concept**
Damage to the facial nerve above the branching of the chorda tympani affects the motor fibers responsible for facial expressions, but spares the taste sensation from the anterior two-thirds of the tongue. The chorda tympani nerve carries taste fibers from the anterior two-thirds of the tongue and parasympathetic fibers to the submandibular and sublingual glands.
**Why the Correct Answer is Right**
The facial nerve (cranial nerve VII) has a complex anatomy, with the chorda tympani nerve branching off above the stylomastoid foramen. Above this branching, the facial nerve carries only motor fibers, which are responsible for facial expressions. Damage to the facial nerve at this level would result in weakness or paralysis of the facial muscles, including the orbicularis oculi, orbicularis oris, and the muscles of facial expression. However, the taste sensation from the anterior two-thirds of the tongue would remain intact, as the chorda tympani nerve carries these fibers below the branching point.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because damage to the facial nerve above the branching of the chorda tympani would indeed affect the taste sensation from the anterior two-thirds of the tongue.
* **Option B:** Incorrect because the facial nerve carries motor fibers responsible for facial expressions, which would be affected by damage above the branching of the chorda tympani.
* **Option C:** Incorrect because the facial nerve carries parasympathetic fibers to the submandibular and sublingual glands, which would be affected by damage above the branching of the chorda tympani.
**Clinical Pearl / High-Yield Fact**
The facial nerve is a complex nerve with multiple functions, including motor, sensory, and parasympathetic. Damage to the facial nerve at different levels can result in distinct clinical presentations, and understanding the anatomy of the facial nerve is crucial for diagnosing and managing facial nerve disorders.
**Correct Answer: C. Damage to the facial nerve above the branching of the chorda tympani would affect the taste sensation from the anterior two-thirds of the tongue.