Conditions: Taste Disturbance (Dysgeusia)
View of the chorda tympani nerve from behind (medial to) the eardrum (tympanic membrane) as it branches off of the facial nerve.
What is the chorda tympani nerve?
Chorda tympani is a nerve that transmits sensation of taste from the front of the tongue to the brain. It also triggers secretion of saliva from some of the salivary glands (submandibular and sublingual glands). There is a left and a right chorda tympani. The taste buds and salivary glands on the left are served by the left nerve, and similarly, the right nerve serves these structures on the right.
The chorda tympani nerve has a complex course from the brainstem to the tongue and its target salivary glands. It travels along the facial nerve from the brainstem through the temporal bone, but then branches from the facial nerve in the middle ear, the space behind the eardrum containing the ossicles (bones) for hearing). Going forward, it passes deep under the temple toward the oral cavity, joining up with the lingual nerve along the way.
Why is the chorda tympani nerve affected by surgery?
There are two main surgical sites in which the chorda tympani nerve may be affected by surgery: the middle ear and the tongue or floor of mouth. Middle ear surgery, including placement of a tympanostomy tube, repairing a perforated eardrum, or more extensive ear surgery may affect the function of the chorda tympani nerve. In the oral cavity, the chorda tympani fibers run with the lingual nerve before branching to the taste buds and sublingual and submandibular salivary glands. These nerve fibers may also be affected by surgery. Depending on the reason for surgery, such as cancer or cholesteatoma, the risk of injury to the chorda tymani may be high, and even unavoidable despite every precaution taken.
What are the symptoms of chorda tympani neuropathy?
Generally, one does not experience any decreased salivary flow when one chorda tympani nerve is nonfunctional, due largely to the abundance of other salivary glands. Taste may be altered with dysfunction o the chorda tympani, and this alteration is usually described as a tendency toward a metallic taste. Fortunately, the taste alteration tends to significantly improve or fully resolve after several months.
How much will chorda tympani neuropathy bother someone?
Degree of bother is very subjective, but overall, the vast majority of people who note an alteration of taste find it to be a minor nuisance. It does not impair ability to eat or drink adequately, and after several months, it is usually no longer noticeable. The perception of saliva production and the ability to eat dry foods seems not be be an issue after chorda tympani injury.