Abstract
Neuralgia of the glossopharyngeal nerve is a rare entity, with an estimated incidence of 0.8 cases per 100,000. 1 The relative frequency compared with trigeminal neuralgia is approximately 1%. 2
Glossopharyngeal neuralgias are classified as either classical or symptomatic; these two types differ mostly by the intercritical pain and sensory deficit in the nerve's territories of distribution seen in the latter type. 3 The International Classification of Headache Disorders, 2nd edition (ICDH-II) 4 includes diagnostic criteria for the classical type of glossopharyngeal neuralgia, which is associated with neurovascular compression in the cerebellopontine angle. The most common offending vessel is the posteroinferior cerebellar artery (PICA), followed by the vertebral artery, the anteroinferior cerebellar artery (AICA), and other vessels or combinations of vessels. 5 An endoscopic anterior view of the normal anatomy of the cerebellopontine angle is shown in figure 1.
This anterior endoscopic view shows a normal right cerebellopontine angle in a cadaver head. The anteroinferior cerebellar artery (AICA) forms a loop close to the facial (VII) and vestibulocochlear (VIII) nerves; the posteroinferior cerebellar artery (PICA) forms a loop anterior to the roots of the lower cranial nerves (PB = petrous bone).
The aim of this report is not to describe a new clinical condition, but to show a rare, exemplary case of glossopharyngeal neuralgia in which a step-by-step diagnostic workup allowed us to make a definitive diagnosis.
A 48-year-old man presented to us with a 13-month history of severe paroxysmal pain located in the left tonsillar fossa and radiating to the posterior wall of the pharynx, lower jaw, and ear. His ENT examination was unremarkable, and previous computed tomography imaging was negative for lesions of the brain, skull, and neck.
Skull x-rays did not reveal an elongated styloid process or calcification of the stylohyoid ligament, ruling out the possibility of Eagle syndrome. 6 Contrast-enhanced magnetic resonance imaging (MRI) of the cerebellopontine angle showed a neurovascular compression between the left PICA and the roots of the lower cranial nerves (figure 2).
Axial T2-weighted MRI reveals the vascular loop of the PICA (blackarrow) compressing the glossopharyngeal nerve against the cerebellum. The course of the glossopharyngeal nerve is visible (white arrow).
We initiated treatment with carbamazepine, considering surgery a second-line treatment that could be proposed if medical treatment proved unsuccessful. The patient's response to medical therapy was only partially satisfactory, but he decided to wait before considering surgery.
Causes of symptomatic glossopharyngeal neuralgia include cerebellopontine angle tumors, nasopharyngeal carcinomas, carotid aneurysms, tonsillar abscesses, neurilemmomas of cranial nerve IX, multiple sclerosis, and Eagle syndrome. Treatment can be medical or surgical. Carbamazepine or gabapentin can be effective in suppressing painful paroxysms. Surgical methods include nerve section and microvascular decompression. The latter can provide complete relief of pain in 76% of patients and substantial improvement in an additional 16%, according to Resnick et al. 7
Glossopharyngeal neuralgia (in both its classical and symptomatic forms) should be considered in the differential diagnosis of paroxysmal oropharyngeal pain. MRI can be useful in demonstrating neurovascular compression in classical glossopharyngeal neuralgia.