Rarely, tumors, including carcinoma, lymphoma or epithelioma of the oropharyngeal-infracranial region or peritonsillar abscess may give rise to pain that is clinically indistinguishable from glossopharyngeal neuralgia.
For idiopathic glossopharyngeal neuralgia, a trial of carbamazepine, gabapentin, pregabalin, or baclofen may be useful. If these are unsuccessful, the conventional surgical procedure had been to interrupt the glossopharyngeal nerve and upper rootlets of the vagus nerve near the medulla but recent observations suggest that a vascular decompression procedure similar to the one used for trigeminal neuralgia and directed to a small vascular loop under the ninth nerve relieves the pain in a proportion of patients.
The common pain and herpetic eruption caused by herpes zoster infection of the gasserian ganglion are practically always limited to the first division (herpes zoster ophthalmicus). Ordinarily, the rash appears within 4 to 5 days or less after the onset of the pain, thereby making the clinical diagnosis difficult; however, treatment should be instituted (see below) based on the clinical likelihood of zoster infection. If the eruption does not appear, some cause other than herpes zoster will almost invariably declare itself; nevertheless, a few cases have been reported in which the characteristic location of pain with serologic evidence of herpes zoster infection was not accompanied by skin lesions.
The acute discomfort associated with the herpetic eruption usually subsides after several days or weeks, or it may linger for several months. It is mostly in the elderly that the pain becomes chronic and intractable. Usually it is described as a constant burning, with superimposed waves of stabbing pain, and the skin in the territory of the preceding eruption is exquisitely sensitive to the slightest tactile stimuli, even though the threshold of pain and thermal perception is elevated. This unremitting postherpetic neuralgia of long duration represents one of the most difficult pain problems with which the physician must deal. Some relief may be provided by application of capsaicin cream, use of a mechanical or electrical cutaneous stimulator, or administration of one of the antiepileptic drugs.
Neuralgia associated with a vesicular eruption caused by the herpes zoster virus may affect the external auditory meatus and pinna and sometimes of the palate and occipital region—with or without deafness, tinnitus, and vertigo—is combined with facial paralysis. This syndrome, since its original description by Ramsay Hunt, has been known as geniculate herpes, and also Ramsay Hunt syndrome (see also Chap. 44). It is clear that the skin of the external ear canal, tympanic membrane and in some patients, the skin behind the ear are supplied by somatic sensory branches that travel with the chorda tympani and greater superficial petrosal nerves and have their cell bodies in the geniculate ganglion.
Treatment with acyclovir, along the lines indicated in Chap. 32, will shorten the period of eruption and the acute pain, but the drug does not prevent its persistence as a chronic pain. There is little data upon which to judge the utility of corticosteroids but they are generally not used (whereas they do provide benefit in Bell’s palsy and antiviral agents are not clearly useful).