Glossopharyngeal neuralgia (GPN), also called vagoglossopharyngeal neuralgia, is characterized by brief but intense pain on one side of the throat, which may radiate within the mouth or into the ear. Attacks are described as sharp, stabbing, or burning in quality. They may occur spontaneously or be provoked by talking, chewing, swallowing, coughing, and yawning. Some sufferers also describe other sensations in the throat such as clicking, scratching, or a foreign body sensation. In rare cases, the pain may become associated with fainting (syncope).
This disorder is similar to trigeminal neuralgia (TN), but involves the glossopharyngeal and vagus cranial nerves (also called the IXth and Xth nerves). Like TN, GPN initially includes periods of remission which decrease in duration over time, while the severity and frequency of painful attacks increase with time.
As with TN, the diagnosis of GPN is established on the basis of a clinical history and normal neurologic, dental, and MRI findings. Unlike TN, carbamazepine and other medications are generally less effective in controlling pain and thus are not typically used in diagnostic testing. Applying anaesthetic solution to the affected area of the mouth or throat—which may temporarily alleviate the pain—has been proposed as a diagnostic test for GPN.
Three forms of GPN can be distinguished: typical GPN, atypical GPN, and secondary GPN. Typical GPN is usually caused by vascular compression of the IXth and Xth cranial nerve rootlets entering the lateral medulla. Atypical GPN involves a prominent associated aching or burning pain in the involved side of the face. Secondary GPN is caused by a tumour injuring the glossopharyngeal nerve in the neck or base of the skull (see Cranial Based Tumours). Only rarely is GPN associated with multiple sclerosis (MS).
Medications used for trigeminal neuralgia can sometimes control GPN pain. Surgical interventions are considered when the pain becomes severe and medical therapy either provides adequate pain relief or causes unacceptable side effects.
A rhizotomy procedure involves sectioning of the glossopharyngeal nerve and upper rootlets of the vagus nerve. This effectively relieves the pain for the majority of sufferers, but may, however, cause swallowing problems due to the nerve injury. The rhizotomy is usually performed with open surgery similar to microvascular deompression (MVD) surgery.
MVD surgery for GPN relieves the compression of blood vessels upon the IXth and Xth cranial nerve rootlets emerging from the lateral medulla. This surgery does not injure the nerves and cures GPN in about three-quarters of patients. Recurrence of GPN is less likely following MVD surgery than rhizotomy procedures.
Percutaneous radiofrequency rhizotomy for GPN is performed with a needle advanced through the cheek to the skull base, directed to produce injury of the IX and X cranial nerves. This procedure involves a higher risk of producing numbness and swallowing difficulties. However, it is well-suited for treatment of secondary GPN, when the tumour has already damaged the nerve function. In these cases, treatment of the tumour itself may reduce the GPN pain. Percutaneous radiofrequency rhizotomy is also an option for sufferers who are not candidates for other more invasive surgical procedures.