Glossopharyngeal Nerve

Nerves that arise from the brain are known as the cranial nerves. There are 12 pairs of cranial nerves in humans. Of these some are sensory, some are motor, and some perform both the functions and therefore also known as mixed nerves. These are denoted by using Roman numbers. Of these 12 pairs, glossopharyngeal nerve is the ninth one (CN IX). It is one of the 10 cranial nerves that emerges out of the brainstem. It comes out from the upper medulla (jugular foramen) rostral to the vagus nerve.

Branches
This nerve has 5 different components with different functions.

• Branchial motor
• Visceral Motor
• Visceral sensory
• General nerve
• Special sensory

These nerves have various branches (afferent and efferent) and they are tympanic, stylopharyngeal, tonsillar, carotid sinus nerve, branches to the posterior of the tongue, lingual branches, a branch to the vagus tympanic.

Functions
The name glossopharyngeal suggests that it is related to the tongue and the thorax. It has a varied number of functions as it serves as a sensory and motor nerve.

• It receives sensory fibers from tonsils, pharynx, middle ear and the posterior of the tongue.
• It receives visceral sensory fibers from the carotid.
• It supplies the parotid gland with parasympathetic fibers through the otic ganglion.
• The stylopharyngeus muscle receives motor fibers from this nerve.
• It is also a part of pharyngeal plexus.

The sensory component of the nerve provides sensory signals from the skin to the external ear, the tympanic membrane surface and 1/3rd of the posterior of the tongue. The motor component helps in voluntary control of the stylopharyngeus muscle, this helps in speech and swallowing. It partly plays a role in regulating blood pressure. The parasympathetic component originates in the inferior salivatory nucleus. The fibers from this nucleus join the nerve fibers exiting from the brainstem.

The exact path of this nerve is as follows. It passes from the medulla oblongata to the flocculus and leaves through the jugular foramen. In the jugular foramen, it has the sheath of dura mater. The glossopharyngeal nerve is anterior to the vagus nerve and lateral to the accessory nerve.

Conditions
This nerve is involved in functions of tasting, swallowing and maintenance of blood pressure. Therefore, any damage or injury affects the mentioned functions. The most common condition of this nerve is the glossopharyngeal neuralgia. The pain caused due to this state lasts for a few minutes in the throat, posterior part of the tongue, ears and tonsils. The symptoms of this include, pain in the back of the throat, tonsils, ear and the back of the tongue. The symptoms are triggered when performing actions such as chewing, talking, coughing.

The cause of this disorder is usually the compression of the nerve by blood vessels. A local anesthetic given causes a nerve block that reduces pain. Anticonvulsants also help in relieving this pain. This disorder is mostly seen in men after the age of 40.

An anesthetic to the back of the throat helps in diagnosis of the nerve, the relief from pain is an indication of glossopharyngeal neuralgia. Glossopharyngeal nerve block also helps in palliative care for tonsillectomy recovery. This block, prevents gagging caused when instruments are inserted into the mouth for the surgery.

The glossopharyngeal nerve just like all the others is very important. There are various other nerves which work together in a complex way to perform various motor and sensory functions smoothly.