Glossopharyngeal nerve

The glossopharyngeal nerve emerges from the brainstem (medulla oblongata), passes through the jugular foramen at the base of the skull, and descends into the neck. The vagus nerve and accessory nerve pass through the same opening, so these three nerves share many similarities while dividing up their tasks. It is also called the ninth cranial nerve because it is the ninth of the twelve pairs of cranial nerves.

Its functions can be broadly divided into five areas.

• Sensation and taste in the back third of the tongue. The facial nerve handles taste at the front of the tongue, while the glossopharyngeal nerve carries taste and touch sensations from the back.
• Sensation in the pharynx, tonsils, and middle ear. The sensation you feel when the inside of your throat is touched travels along this nerve. In the gag reflex, the glossopharyngeal nerve carries the sensory signal, while the vagus nerve responds by moving the throat muscles.
• One muscle used in swallowing. It activates a small muscle called the stylopharyngeus, which pulls the pharynx upward during swallowing.
• Saliva production. It signals the parotid gland, a large salivary gland in front of the ear, to produce saliva. The sharp, tingling sensation below your ears when you think of sour food is related to this pathway.
• Blood pressure sensing. At the branching point of the carotid artery on the side of the neck, there are small sensors that measure blood pressure and blood oxygen levels. The glossopharyngeal nerve sends this information to the brainstem, allowing the body to adjust heart rate and vascular tone appropriately.

When the glossopharyngeal nerve is working well, we do not notice it. The natural rise and fall of your throat when you swallow, your mouth staying moist, and not feeling dizzy when you get up from lying down are all results of this nerve doing its job.

Sometimes its activity is more noticeable. Typical examples include gagging when a toothbrush reaches deep into your throat, or coughing when a cotton swab touches the inside of your ear (this cough is due to a branch of the vagus nerve). The tickling sensation you feel when the area near your uvula is touched also travels along the same sensory pathway.

Rarely, stabbing pain lasting a few seconds at a time may recur on one side at the back of the tongue, in the throat, or deep inside the ear. It often occurs when swallowing, talking, or coughing, and is called glossopharyngeal neuralgia. It is uncommon, but if this pain keeps recurring, you should first see a specialist to identify the cause rather than trying to resolve it by loosening up your body.

One of the least noticeable functions of the glossopharyngeal nerve is monitoring blood pressure. Where the carotid arteries on either side of the neck divide into two branches, there is an area that senses stretching of the vessel wall (the carotid sinus) and a small nodule that measures oxygen levels (the carotid body). When blood pressure rises, the vessel wall stretches, and this information travels along the glossopharyngeal nerve to the brainstem. The brain then slows the heart and widens the blood vessels to lower blood pressure. When your vision briefly darkens after you suddenly stand up from lying down and then quickly returns, this is also part of this automatic adjustment process.

For this reason, it is best to avoid pressing or rubbing firmly with your thumb and index finger over the pulse at the side of your neck. Pressure on these sensors can make the brain mistakenly interpret that blood pressure has risen, causing heart rate and blood pressure to drop suddenly. During massage, too, the basic principle is to treat the sides of the neck gently and avoid the areas where you can feel a pulse.

• Vagus nerve. Although it exits through the same opening, the vagus nerve is a long nerve that descends from the neck into the chest and abdomen, looking after the internal organs as a whole. The glossopharyngeal nerve has a more limited territory around the tongue, pharynx, and carotid artery.
• Facial nerve. It handles taste at the front of the tongue and some saliva production. It works alongside the glossopharyngeal nerve, with the two sharing responsibility for taste in the mouth.
• Hypoglossal nerve. This is a motor nerve that moves the tongue, so its role differs from that of the glossopharyngeal nerve, which carries sensory information.

Integrative manual therapy (IMT) places importance on the passages through which the cranial nerves travel. Because the glossopharyngeal nerve passes through a narrow opening at the base of the skull alongside the vagus and accessory nerves, this approach describes tension in this region as connected to the condition of the upper neck and the base of the skull (craniovertebral junction). For people who report a catching sensation in the throat when swallowing or stiffness in the jaw and front of the neck, practitioners may therefore also examine tissues along this nerve's route, such as those around the suboccipital muscles or hyoid muscles. This approach does not involve touching the glossopharyngeal nerve directly; rather, it examines tension in the surrounding muscles and membranous tissues.

• Take your time when swallowing. Eating in a hurry gives the pharyngeal muscles no time to rest. It is best to chew each mouthful thoroughly and avoid swallowing with your head tilted too far back.
• Keep the front of your neck relaxed. A prolonged head-down position (forward head posture) keeps the muscles beneath the jaw and at the front of the neck under constant tension. Once an hour, gently lift your head and tuck your chin slightly.
• Keep your mouth from drying out. Drinking water frequently helps the salivary glands work more easily and makes swallowing smoother.
• If swallowing is often uncomfortable, do not simply put up with it on your own. Refer to the Dysphagia article, and see a specialist if symptoms persist.