The glossopharyngeal nerve is one of twelve cranial nerves that connect to the brain. Like the other cranial nerves, the glossopharyngeal nerve is paired — there's one on each side of your brain. The glossopharyngeal nerve connects to several important parts of your body, such as the middle ear, neck, salivary glands, tonsils, and tongue. Disorders of this nerve make it difficult to swallow and detect sensations in the throat and middle ears.
Many conditions can damage this nerve or affect its function, but you can learn more about how to prevent them below.
What Is the Glossopharyngeal Nerve?
The glossopharyngeal nerve (also known as cranial nerve 9) is the ninth of the cranial nerves arising from the brainstem. This nerve carries three types of fibers:
- Motor nerve fibers that control muscle movements
- Sensory nerve fibers that carry sensory information to the brain
- Parasympathetic fibers that control organs and functions not under voluntary control
The glossopharyngeal nerve has several branches. The tympanic branch supplies the middle ear. The stylopharyngeal branch controls the stylopharyngeus muscle during swallowing and speaking. Its other branches include the tonsillar nerve, carotid sinus nerve, lingual branches, and a communicating branch linked to the vagus nerve (cranial nerve 10). Its pharyngeal branches communicate with other nerves to coordinate swallowing.
Glossopharyngeal Nerve Function
The glossopharyngeal nerve carries many types of nerve fibers and has multiple functions, regulating:
- Taste sensations from the rearmost third of the tongue
- Sensations from the tonsils, back of the throat, middle ear, and the area behind the ear
- The stylopharyngeus muscle during swallowing. The glossopharyngeal nerve works with several others to coordinate the complex act of swallowing food and keeping the airway safe from aspirating food and drink.
- Stimulation of the parotid salivary glands to produce saliva for swallowing
- Information sent to the brain from the carotid sinus and carotid body. These structures help regulate your blood pressure and blood oxygen and carbon dioxide levels. The vagus nerve also carries information from these structures.
Where Is the Glossopharyngeal Nerve Located?
A better understanding of glossopharyngeal nerve anatomy promotes a superior understanding of the various disorders that cause its malfunction. This cranial nerve arises from the medulla oblongata, a part of the brainstem. It exits the skull through an opening called the jugular foramen.
Beneath the skull, the glossopharyngeal nerve runs down with the internal carotid artery and the internal jugular vein, two important blood vessels carrying blood to and from the brain. Near the soft palate, this nerve separates from the blood vessels and enters the throat. Along the way, it extends various branches. In the throat, it splits into the lingual branch and pharyngeal branches.
What Conditions Affect the Glossopharyngeal Nerve?
Glossopharyngeal nerve palsy. An injury or stroke can cause this condition. The nerve's functioning is impaired, leading to ear pain, difficulty swallowing, and altered taste on the back of the tongue. Sensations in the throat, palate, and tongue are reduced, and you may have a dry mouth because of reduced saliva production.
You may not observe typical symptoms, though, because isolated glossopharyngeal nerve palsy is rare. The nerve travels close to the vestibulocochlear (cranial nerve 8), vagus (cranial nerve 10), and accessory (cranial nerve 11) nerves. Injuries or strokes almost always involve more than one of these important nerves and cause more widespread symptoms.
Diabetes is a risk factor for cranial nerve palsies, especially if it is not properly treated.
Glossopharyngeal neuralgia. This condition causes episodes of pain. The areas affected include the jaw, the back of the tongue, the tonsillar area, and the ear. The pain is generally focused on one side and appears and vanishes abruptly. Episodes can follow each other within minutes or not occur for days at a time. The pain may be triggered when you talk, laugh, or swallow. The pain can be severe enough to affect eating.
The most common cause of glossopharyngeal neuralgia is pressure on the nerve root. Internal carotid artery dissection or an aneurysm can compress and damage the glossopharyngeal nerve.
Some other causes include:
- Inflammatory diseases like Sjogren disease
- Infections in the mouth and tonsillar area
- Demyelinating disorders like multiple sclerosis
- Cancer of the brain, throat, mouth, tonsils, and larynx
- Injury during surgical procedures
- Bony malformations
Regular painkillers don't work in cases of glossopharyngeal neuralgia. Your doctor will first prescribe medicines like gabapentin, pregabalin, or carbamazepine. They may add more medicines or swap them out based on your response to the treatment. Surgery is an option if medicines don't provide relief.
Injuries. Some medical procedures can also injure this important nerve.
- Tonsillectomy. The scar tissue formed can stretch and distort nearby structures, including the glossopharyngeal nerve.
- Carotid endarterectomy. This is a procedure used to clear your carotid arteries by removing deposited fats. The procedure improves blood supply to the brain but may damage the glossopharyngeal nerve that runs along the artery.
- Laryngeal mask airway. This is a tube inserted into your throat to help you breathe. It may injure structures in the throat, such as the glossopharyngeal nerve.
Nerve disorders can often be a sign of an underlying serious disease process. You should consult your health care provider if you experience any of these symptoms.
Signs Something Could Be Wrong With Your Glossopharyngeal Nerve
The glossopharyngeal nerve is involved in several functions of the mouth and throat. Disorders of this nerve can cause:
- Swallowing difficulty (dysphagia)
- Drymouth, caused by less production of saliva from the parotid salivary gland
- Gag reflex weakening. The absence of the gag reflex on one side is especially characteristic of glossopharyngeal nerve palsy
- An inability to open your mouth
- Numbness at the back of your mouth
The glossopharyngeal nerve has a role in regulating blood pressure, but hypertension (high blood pressure) only happens if both these nerves are damaged. Injury to one glossopharyngeal nerve does not affect blood pressure.
How to Keep Your Glossopharyngeal Nerve Healthy
The glossopharyngeal nerve needs no specific care measures, but a healthy lifestyle is important. To keep your nervous system healthy, you should:
- Avoid smoking.
- Limit alcohol consumption.
- Eat a healthy diet with all the essential micronutrients.
- Seek treatment if you have diabetes.
The glossopharyngeal nerve is among a few nerves that contain motor, sensory, and parasympathetic fibers. It participates in multiple functions, and injuries or diseases affecting it can adversely affect your quality of life.