Paraganglioma

Paragangliomas are neuroendocrine tumours arising from paraganglia of the autonomic nervous system. In the head and neck, they arise from parasympathetic paraganglia at the carotid bifurcation (carotid body tumour), along the vagus nerve (vagal paraganglioma) and in the temporal bone. Jugular paragangliomas (glomus jugulare) arise in the jugular bulb within the jugular foramen; tympanic paragangliomas (glomus tympanicum) arise on the cochlear promontory of the middle ear^[1]. A substantial minority are hereditary, most often from mutations in the succinate dehydrogenase genes (SDHx), and hereditary tumours are more often multiple.

The Fisch classification grades temporal-bone paragangliomas from class A (confined to the middle ear) through B (tympanomastoid), C (infralabyrinthine and petrous apex with carotid involvement, subdivided C1–C4) and D (intracranial extension)^[2]. The Glasscock–Jackson classification separately grades tympanic and jugular tumours by their extent^[3]. Both are used to plan the approach and predict the risk to cranial nerves.

Pulsatile tinnitus and conductive hearing loss are the commonest early symptoms; a red, pulsatile mass may be seen behind the tympanic membrane. Jugular tumours cause lower cranial-nerve palsies (IX–XII), producing dysphagia, hoarseness and aspiration, and may involve the facial nerve. Because the tumours grow slowly, cranial-nerve palsies often develop gradually and are well compensated. Rarely, tumours secrete catecholamines and cause hypertension and palpitations.

High-resolution CT shows irregular, “moth-eaten” erosion of the jugular foramen and the relation to the carotid canal, facial canal and otic capsule. MRI shows a “salt-and-pepper” pattern from flow voids and avid enhancement, and defines intradural extension. Catheter angiography defines the feeding arteries (especially the ascending pharyngeal artery) and venous drainage and allows preoperative embolisation; balloon test occlusion is performed if carotid sacrifice is possible. All patients should be screened for catecholamine secretion (plasma or urinary metanephrines) and offered genetic testing^[1].

Treatment is tailored to age, tumour size and growth, cranial-nerve function and comorbidity. Small tympanic tumours are cured by transcanal or transmastoid resection with a low risk. For jugular tumours, options include observation (in older patients or those with slow-growing tumours), stereotactic radiosurgery or fractionated radiotherapy, which provides high tumour control with a lower risk of new cranial-nerve deficits, and surgical resection. In a systematic review, gross-total resection achieved high control but at the cost of new lower cranial-nerve deficits in a substantial proportion of patients, whereas radiotherapy achieved similar control with fewer deficits^[1]. Subtotal resection followed by radiosurgery is an increasingly common compromise.

• Embolise one to two days before surgery to reduce blood loss.
• The infratemporal fossa type A approach with facial-nerve transposition gives control of the jugular bulb and internal carotid artery^[2].
• Control the sigmoid sinus proximally and the internal jugular vein in the neck; bleeding from the inferior petrosal sinus is packed within the jugular bulb.
• Leave tumour on the medial wall of the jugular bulb when the lower cranial nerves are still functioning.
• Treat catecholamine-secreting tumours with alpha-blockade before surgery.

Tumour control is high with all modalities. Function after surgery depends mostly on the lower cranial nerves; acute bilateral deficits are poorly tolerated, so patients with multiple tumours need careful planning. Swallowing therapy, vocal-cord medialisation and facial reanimation help rehabilitation.