What it is
Paragangliomas are tumors that arise from paraganglia — small clusters of cells derived from the neural crest that are distributed along blood vessels and nerves. In the temporal bone they occur in two main locations, and the distinction matters because it drives symptoms and management:
Glomus tympanicum tumors arise within the middle ear, on the promontory along the course of the tympanic branch of the glossopharyngeal nerve. They are generally smaller and more contained, and are often visible on examination as a red mass behind the eardrum.
Glomus jugulare tumors arise at the jugular bulb, at the base of the skull. Because of their location they involve the jugular foramen, where the ninth, tenth, and eleventh cranial nerves exit the skull, and they can extend intracranially. These are more complex to treat.
Both are strikingly vascular, which shapes both the symptoms they produce and how they must be approached surgically.
Symptoms
- Pulsatile tinnitus — a whooshing or thumping sound synchronized with the heartbeat, the most characteristic symptom
- Conductive hearing loss from the mass contacting or restricting the eardrum and ossicles
- Aural fullness
- A red or bluish mass visible behind the eardrum on examination
- Bleeding from the ear canal, particularly if the tumor erodes through the eardrum
- Hoarseness, swallowing difficulty, or tongue weakness, indicating involvement of the lower cranial nerves — seen with glomus jugulare tumors
- Facial weakness, in more extensive tumors
- Dizziness or imbalance
Diagnosis
CT of the temporal bone shows the bony detail and the characteristic pattern of erosion, which helps distinguish a glomus jugulare tumor from a glomus tympanicum. MRI with contrast, often with dedicated vascular sequences, defines the soft tissue extent, involvement of the jugular bulb and carotid artery, and any intracranial extension.
Biochemical screening is important. A minority of these tumors secrete catecholamines, and detecting that before any intervention changes perioperative management substantially. Screening is done with blood or urine testing for metanephrines.
Genetic testing is frequently recommended, given the meaningful proportion of paragangliomas linked to hereditary mutations — most commonly in the succinate dehydrogenase (SDHx) genes. Results affect surveillance for additional tumors, including elsewhere in the head, neck, chest, and abdomen, and have direct implications for relatives.
Because these tumors are so vascular, biopsy through the ear canal should be avoided; the diagnosis is made on imaging.
Management
Observation. Many paragangliomas grow slowly enough that serial imaging is a sound strategy, particularly for small tumors, for older patients, and when cranial nerve function is currently intact and the risks of treatment are material.
Radiation therapy and stereotactic radiosurgery. Focused radiation aims to arrest growth while preserving the cranial nerves, and has become a primary option for many glomus jugulare tumors specifically because of the risk surgery poses to the lower cranial nerves. See Gamma Knife stereotactic radiosurgery.
Surgery. Removal is well suited to glomus tympanicum tumors confined to the middle ear, which can often be excised completely through the ear with good results. For glomus jugulare tumors, surgery is more extensive and the decision weighs complete removal against the risk to the ninth through twelfth cranial nerves, which control swallowing, voice, and tongue movement.
Preoperative embolization — blocking the tumor’s blood supply through a catheter shortly before surgery — is frequently used to reduce blood loss during removal of these highly vascular tumors.
Management of paragangliomas is typically multidisciplinary, drawing on neurotology, neurosurgery, interventional neuroradiology, radiation oncology, endocrinology, and genetics depending on the individual tumor.