The Glossopharyngeal Nerve and What it Does (2024)

The glossopharyngeal nerve, which is also called the ninth cranial nerve, has both sensory (sensation) functions and motor (movement) functions in the body, as well as specialized sensory function and parasympathetic function.

The glossopharyngeal nerve is involved in taste, salivation, swallowing, speech, the tonsils, blood flow to the brain, and the middle ear.

Anatomy

The 12 cranial nerves exist in symmetric pairs that emerge from the brain itself, as opposed to the rest of your nerves, which branch off from the spinal cord.

As most of the cranial nerves do, the glossopharyngeal nerve emerges from the front of the brainstem, which sits low at the back of your brain and connects the brain to the spinal cord.

Structure and Location

The glossopharyngeal nerve exits the cranial cavity (skull) through a structure called the jugular foramen, which is a large opening in the base of the skull. It then gives off a branch called the tympanic nerve, which goes through the temporal bone to reach the middle ear.

From the ear, the lesser petrosal nerve branches off and continues to the otic ganglion (a collection of nerve cells in the ear.) The lesser petrosal nerve then runs along the auriculotemporal nerve to the parotid gland, which is a salivary gland in the cheek.

Meanwhile, the main glossopharyngeal nerve travels downward between the internal carotid artery and the internal jugular vein and then curves forward to form an arch on the side of your neck on top of the stylopharyngeus muscle and the middle pharyngeal constrictor muscles high in the throat. At that point, the glossopharyngeal nerve sends off the carotid sinus nerve, which then runs downward in the neck to the carotid artery.

Next, it runs under the hyoglossus muscle, which comes up the side of the neck and connects to the tongue. It then gives off its three terminal branches:

1. Pharyngeal branch: Joins with fibers of the vagus nerve (the tenth cranial nerve) to form the pharyngeal plexus.
2. Lingual branch: Connects to the back third of your tongue. (The lingual branch of the glossopharyngeal nerve shouldn't be confused with the lingual nerve, which is a branch of the trigeminal nerve.)
3. Tonsillar branch: Forms a network of nerves called the tonsillar plexus.

Anatomical Variations

Many nerves have anatomical variations that doctors, especially surgeons, need to be familiar with so they don't inadvertently injure them during procedures. Knowing about them can also help diagnose problems with nerve function.

In most people, the glossopharyngeal nerve curves around the front of the stylopharyngeus muscle, but in some cases, it penetrates this muscle instead.

Some research has shown that a small percentage of people have abnormal connections between the glossopharyngeal and vagus nerves where they travel close together inside the skull. That's especially important during surgery in that area to keep the nerve fibers from being cut.

Function

The glossopharyngeal nerve serves a variety of functions in the head and neck through different types of nerve fibers and its various branches.

Sensory Function

The glossopharyngeal nerve plays a sensory role in numerous important structures. In the middle ear, via its tympanic branch, it becomes part of the tympanic plexus. That's a network of nerves that provides sensory function to the middle ear, the eustachian tube, and the internal surface of the tympanic membrane (your eardrum).

The carotid sinus nerve, which connects to the carotid artery, provides information to your brain about blood pressure and oxygen saturation.

The pharyngeal branch provides sensation to the mucous membranes in the opening to the throat between the soft palate and epiglottis.

The tonsillar branch supplies sensation to the tonsils.

Specialized Sensory Function

The lingual branch performs the specialized task of transmitting taste information to your brain. It connects with the taste buds on the rear third of your tongue and down into the throat, and it also provides that area with general sensory information about things like touch, temperature, and pain.

The chorda tympani nerve, which is a branch of the facial nerve (the seventh cranial nerve), innervates the forward two-thirds of the tongue. The lingual branch and chorda tympani provide what's called inhibition to each other's signals, meaning that they dampen the signals that are sent to the brain. Experts think this might happen in order to allow the brain to tell the difference between a wider variety of tastes.

Damage to one of these nerves takes away that inhibiting effect and can lead to an increase in your perception of particular tastes as well as an increase in tongue-related pain.

Motor Function

The glossopharyngeal nerve provides motor function to the stylopharyngeus muscle. Located in the pharynx, which is the portion of your throat behind the nose and mouth, this muscle is involved in swallowing. It shortens and widens the pharynx and lifts the larynx (commonly called the voice box) when you swallow.

Parasympathetic Function

The sympathetic and parasympathetic nervous systems are part of the autonomic nervous system. They work to counterbalance each other. The "fight-or-flight" response to danger or stress comes from sympathetic activity. Parasympathetic activity deals with what's often called "rest-and-digest" functions—in other words, the normal activity that your body engages in when you're not in a situation that requires an intense physical reaction.

The lesser petrosal nerve of the glossopharyngeal nerve, which connects to the parotid gland, contains parasympathetic fibers and stimulates the release of saliva, which is called a secretomotor function. This is part of the parasympathetic nervous system because saliva is involved in the digestive process.

Associated Conditions

Problems with the glossopharyngeal nerve can impact all of the processes it's involved with. Damage to the nerve can be caused by injury or surgery to the head and neck, as well as by strokes, diseases that affect nerve function, or tumors that grow on or compress the nerve.

Common surgical and medical-procedure causes of glossopharyngeal damage include:

• Tonsillectomy
• Sleep apnea surgery
• Skull base surgery
• Carotid endarterectomy

Among the more serious consequences of glossopharyngeal dysfunction are:

• Loss of the carotid sinus reflex, leading to diminished blood flow, which impairs brain function
• Dysphagia, which is problems with swallowing
• Dysphonia, a voice disorder due to spasms in the larynx that causes the voice to break and sound tight or strained
• Loss of the gag reflex
• Loss of taste in the rear third of the tongue
• Reduced salivation
• Glossopharyngeal neuralgia

Glossopharyngeal Neuralgia

Neuralgia is pain due to nerve damage. In glossopharyngeal neuralgia, the primary symptom is pain in the throat and base of the tongue that's triggered by swallowing, chewing, coughing, and yawning. The pain is described as sharp and may impact the tonsils and the lower jaw as well. In some, the pain comes and goes, while in others, it's constant.

Some people with glossopharyngeal neuralgia may also have vagus nerve involvement, which leads to symptoms including:

• Abnormal heart rhythms
• Low blood pressure
• Fainting
• Seizures
• Cardiac arrest

Rehabilitation

Treatment of glossopharyngeal dysfunction depends mainly on the cause of the problem. In some cases, damage to the nerve may heal on its own over time.

The cause of glossopharyngeal neuralgia is often never determined. In those cases, the goal of treatment is to manage symptoms. Standard neuralgia treatments include antidepressants and anticonvulsants.