The glossopharyngeal nerve is the ninth cranial nerve that originates in the brain and controls taste perception, swallowing, and gland function. It can be damaged by tumors, infections, or injuries, causing difficulty swallowing, pain, and dry mouth. Treatment includes antiepileptic drugs and surgery, which can be monitored to avoid nerve damage.
The glossopharyngeal nerve is also called the ninth cranial nerve. Cranial nerves are vital nerves that arise from the brain that help the brain control muscles, process the five senses, and control glands in the body. As its name suggests, the glossopharyngeal nerve originates in the brain near the base of the skull, exits the skull through a large hole called the jugular foramen, and ends at the back of the mouth and throat. The glossopharyngeal nerve enables the perception of taste in the posterior part of the tongue, transmits sensations of pain and touch from the throat and tongue, and exerts control over the muscles used during swallowing.
It is difficult to evaluate the glossopharyngeal nerve alone, but doctors typically examine the gag reflex and taste on the posterior tongue to determine glossopharyngeal function. Isolated ninth nerve injuries are extremely rare. Tumors at the junction of the cerebellum and pons in the brainstem can damage the eighth nerve, which mediates balance and hearing, as well as the ninth nerve. Masses near the jugular foramen can compress the ninth, tenth, and eleventh nerves. Diphtheria can cause ninth nerve palsy. Swallowing-associated attacks of unconsciousness, called swallowing syncope, are rare complications of ninth and tenth nerve injuries.
Glossopharyngeal nerve abnormalities cause difficulty swallowing. Affected patients will notice impaired taste in the posterior third of the tongue and palate. There may be reduced sensation or pain on the back of the tongue, palate and throat. The gag reflex is absent in such cases. Parotid gland dysfunction leads to decreased saliva production and dry mouth.
With attacks lasting seconds to minutes, glossopharyngeal neuralgia is a condition in which you experience recurring bouts of shooting pain in your ear, throat, tonsils, and tongue. The cause of neuralgia is irritation of the glossopharyngeal nerve due to pressure from nearby blood vessels, tumors, growths, or infections at the base of the skull, mouth, or throat. Activities that trigger pain attacks include swallowing, talking, laughing, coughing, or chewing. Slow heartbeats and fainting with severely painful episodes have occurred. When surgical treatment isn’t obvious, antiepileptic drugs, such as gabapentin, phenytoin, and carbamazepine, and some antidepressants, such as amitriptyline, are effective in managing symptoms.
In neurosurgery near the skull base, there is a risk of injury to the cranial nerves, including the glossopharyngeal nerve, which can be avoided by monitoring during the case. Electrical stimulation of nerve trunks and electromyographic recordings facilitate identification of cranial nerves before the operation begins. These techniques also monitor the cranial nerves during the surgical removal of tumors located at the base of the skull. As the removal of the tumor progresses, the surgeon can ensure that surgical trauma to the nerve does not occur by observing changes in the extent, shape, and contour of the responses.
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