2.1 Glossopharyngeal Neuralgia
By Jeffrey A. Brown, MD, FACS, FAANS (USA)
(Author’s Note: The information contained in this article is not intended to provide individual medical advice, diagnosis, or treatment or to induce the reader to seek care with any specific physician. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care treatment, and never disregard professional medical advice or delay in seeking it because of something you have read here.)
Glossopharyngeal neuralgia (GPN) was first described by the one of the first modern neurosurgeons, Walter Dandy, as “paroxysmal pain frequently brought on by eating and swallowing with involvement of the root of the tongue and pharynx, with radiation to the throat and/or the deep ear structures”.
This description is still accurate.
What is the glossopharyngeal nerve?
It is the ninth of the 12 cranial nerves, meaning the nerves that directly enter or exit the brain, not the spinal cord, and it is anatomically closely related to the tenth cranial nerve, the vagus nerve. As the preceding definition notes, the glossopharyngeal nerve provides sensation to the throat and base of the tongue, the deep middle ear, and also the parotid gland. The parotid gland is at the base of the jaw. Injury to it will cause a dry mouth. The ninth cranial nerve provides taste sensation to the base of the tongue and some motor function to a swallowing muscle of the throat.
Dandy’s definition was used by Peter Jannetta to select patients for whom he first performed vascular decompression of the vagoglossopharyngeal complex as the most appropriate treatment for this entity. Note that Jannetta spoke of decompressing two nerves: the vagus and the glossopharyngeal. Why? The glossopharyngeal and vagus nerves compose a web of fascicles (slender bundles) such that a vessel in contact with the 9th nerve will also be in contact with the lower fibres of the 10th nerve. These also are sensory to the throat.
Distinguished trigeminal and glossopharyngeal neurosurgeons believe that glossopharyngeal neuralgia is an inaccurate description of this entity leading to neuropathic (stabbing) ear and throat pain. Glossopharyngeal neuralgia is more appropriately categorized as vagoglossopharyngeal neuralgia when caused by a vascular compression because of the close relationship of the fibrous web that enters the jugular foramen at the skull base. This is the opening in the skull that also allows exit from the brain of the large jugular vein, which drains blood from one side of the brain. For this reason, efforts to treat GPN by a rhizotomy, a heat injury to the nerve performed with a special needle, is a concern. The vein can be punctured. Surgeons who choose to section the glossopharyngeal nerve rather than decompress it have learned that they must also section the sensory fibres to achieve adequate pain relief. This leads to permanent, and sometimes uncomfortable, numbness in the throat. The controversy remains. Is GPN better treated by sectioning the glossopharyngeal nerve and adjacent sensory fibres of the vagus nerve or by attempting to decompress it?
What happens to the body with injury to the vagus nerve near the base of the skull? If the motor fibres of the nerve are injured, there can be weakness of the palate, giving the voice a nasal element. Trouble with swallowing follows weakness of the pharyngeal (throat) muscles. There may be weakness or even paralysis of the vocal cords, causing hoarseness. One of the lesser-known issues with vagoglossopharyngeal neuralgia is that, when the vagus nerve is involved, there can be speech difficulty, such as lowered volume of speech, hoarseness with ongoing effort, or perhaps a chronic cough.
The good news is that GPN is surgically treatable. In Jannetta’s series, 79% of 39 patients treated over the course of 24 years had immediate pain relief, and 76% had continuing complete relief with follow-up of 6 months to 14 years, with a mean of 4 years. Many more series of patients by other centres have confirmed the benefits of glossopharyngeal nerve decompression for GPN. There has also been a small study of decompression surgery of the lower cranial nerves specific for dysphonia , that is, speech quality issues including chronic cough, breathing irregularity, and hoarseness.
Finally, it may be possible for a person to have both trigeminal and glossopharyngeal neuralgia. When there is ear pain, it may not be clear whether it is from trigeminal or glossopharyngeal neuralgia.
Choose your physician with care to find one who understands the nuances of your care, and you should do well.
