Clinical Significance and Management of Jacobson's Nerve Issues

Anatomy and Function

The American College of Radiology notes that Jacobson's nerve (tympanic nerve) is a branch of the glossopharyngeal nerve (CN IX) that supplies sensory innervation to parts of the middle ear, mastoid air cells, and eustachian tube 1
The glossopharyngeal nerve provides branchial motor innervation to the stylopharyngeus muscle, visceral motor parasympathetic innervation to the parotid gland, sensory innervation to the posterior tongue, pharynx, and middle ear via Jacobson's nerve, and visceral sensory innervation to the carotid sinus 1, 2

Glossopharyngeal neuralgia presents with severe, paroxysmal pain in the oropharyngeal and otic regions, typically triggered by swallowing, according to the British Journal of Anaesthesia 3
Pain can be experienced in the ear only (via Jacobson's nerve) and therefore confused with temporomandibular disorders, and may also be confined to the posterior part of the tongue 3

The American College of Radiology recommends MRI as the preferred imaging modality for investigating glossopharyngeal nerve pathology, particularly for evaluating the brainstem, intracranial course, and neurovascular compression 1, 2
CT neck is complementary to MRI in assessing skull base erosion, deep space neck masses, intratumoral calcification, bony margins of the jugular foramen, and extracranial course of CN IX 2, 3, 4

Glossopharyngeal neuralgia is typically caused by neurovascular compression, similar to trigeminal neuralgia, according to the British Journal of Anaesthesia 3
Other causes include trauma, elongated calcified stylohyoid ligament, neoplasms along the course of the nerve, intraparenchymal lesions, vascular malformations, infarctions, demyelinating lesions, and inflammatory abnormalities 1, 2, 3

The British Journal of Anaesthesia notes that carbamazepine is the first-line drug treatment for glossopharyngeal neuralgia, with oxcarbazepine being equally effective with fewer side effects 3
Other medications with some evidence of efficacy include lamotrigine and baclofen 3
Microvascular decompression (MVD) is the only non-ablative surgical procedure and can be performed for glossopharyngeal neuralgia, though it is technically more difficult than for trigeminal neuralgia 3

Noniatrogenic isolated syndromes involving the glossopharyngeal nerve are very rare, according to the Journal of the American College of Radiology 2
Nerve root section or nerve ablation results in variable degrees of dysphagia and ipsilateral sensory loss on the pharynx and posterior tongue 2