What are the clinical manifestations of damage to the chorda tympani branch of the facial nerve?

The chorda tympani is a branch of the facial nerve, originating from the intratemporal segment of the facial nerve canal. After the chorda tympani branch of the facial nerve is damaged, the clinical manifestations generally include incomplete eyelid closure, decreased saliva secretion, hypogeusia or anosmia, facial swelling, sensory decline, and more. Detailed analyses are as follows:

1. Incomplete Eyelid Closure: It typically manifests as relaxation of the lower eyelid, atrophy of the everted upper eyelid, inability to fully close the eyelids, and loss of protection for the eyeball, which may lead to vision impairment over time.

2. Decreased Saliva Secretion: On the side of the facial nerve damage affecting the chorda tympani, saliva secretion decreases significantly. Patients often feel dryness in their mouths, while the other side may experience drooling.

3. Hypogeusia or Anosmia: It mainly manifests as a decrease in taste sensation on the anterior two-thirds of the tongue, which may progress to complete loss of taste, making food taste bland.

4. Facial Swelling: Severe damage to the chorda tympani branch may cause inflammation, leading to swelling and pain on one side of the face.

5. Sensory Decline: Due to nerve damage, overall sensory decline occurs, resulting in facial numbness.

In addition, there are other clinical manifestations, such as a distorted mouth corner. If these symptoms appear, it is recommended to seek medical attention promptly, undergo examinations as advised by the doctor, receive a definitive diagnosis, and start treatment as early as possible to facilitate recovery.