Glomus Tympanicum Tumour

Glomus tympanicum tumour is a benign, slow growing, highly vascular paraganglioma arising from glomus bodies (paraganglionic tissue) on the cochlear promontory of the middle ear. It is associated with the tympanic branch (Jacobson nerve) of the glossopharyngeal nerve. It is the commonest tumour of the middle ear, and the second most common paraganglioma of the temporal bone (after glomus jugulare).

It is seen mainly in middle aged women (peak age 40 to 60 years; female-to-male ratio of about 4 to 6:1), with an incidence of about 1 in 1.3 million.

Most are sporadic, but about 10 to 30 percent are familial. They carry germline mutations in succinate dehydrogenase subunits (SDHD in the commonest, SDHB, SDHC, SDHA, SDHAF2), which also predispose to pheochromocytoma and other paragangliomas, so genetic testing is advised.

Multicentric tumours occur in 10 percent (sporadic) and up to 50 percent in hereditary disease. Secretory (catecholamine producing) tumours occur in 1 to 4 percent, and malignancy (metastases) in 2 to 4 percent.

Classification (Fisch):

• class A: tumour limited to the middle ear cleft (glomus tympanicum)
• class B: tympanomastoid tumour with no infralabyrinthine compartment involvement
• class C: involves the infralabyrinthine compartment and the petrous apex (glomus jugulare)
• class D: intracranial extension

The Glasscock-Jackson classification:

• type I: small tumour limited to the promontory
• type II: completely filling the middle ear space
• type III: filling the middle ear and extending into the mastoid
• type IV: extending through the tympanic membrane into the ear canal, or anteriorly to the carotid

• Pulsatile tinnitus (the commonest symptom, in about 80 percent), synchronous with the heart beat, which may be suppressed by carotid compression.
• Conductive hearing loss (from the mass in the middle ear), aural fullness, and, less often, sensorineural loss if extended to the cochlea.
• Otoscopy: a red, pulsatile mass behind an intact tympanic membrane (rising sun sign), blanching with positive pneumatic otoscopy (Brown sign, blanching of the mass with positive pressure applied through the otoscope, in about 20 to 30 percent), or a polypoid vascular mass in the ear canal in larger tumours, with bleeding on manipulation.
• Otalgia, otorrhoea, and bleeding from the ear in advanced cases; vertigo and facial weakness (rare, if the tumour extends to the facial canal or labyrinth).
• Cranial nerve involvement (IX to XII) is typical of jugular tumours and suggests extension if present; catecholamine symptoms (headache, palpitations, sweating, hypertension) in secretory tumours.

• Otoscopic and otomicroscopic examination; avoid biopsy (the risk of severe haemorrhage).
• Audiometry: conductive or mixed loss; tympanometry shows pulsations (a pulsatile tracing).
• High resolution CT of the temporal bone: a soft tissue mass on the cochlear promontory, with intact bone around the jugular foramen, ossicular erosion or displacement, and extension into the hypotympanum and mastoid; distinguishes tympanicum (promontory, intact jugular plate) from jugulare (jugular foramen erosion).
• MRI with gadolinium and MR angiography: intensely enhancing mass, with the "salt and pepper" appearance (flow voids) in tumours above 2 cm. It defines extension to the carotid canal, jugular bulb and intracranial space.
• Selective digital subtraction angiography (rarely required) defines the feeding vessels.
• Exclude the differential diagnoses: aberrant internal carotid artery, high jugular bulb (dehiscent jugular bulb), persistent stapedial artery, vascular tumours, meningioma, adenoma, schwannoma, cholesterol granuloma, and middle ear effusion (the retrotympanic mass).
• Biochemical screening for catecholamine secretion: plasma free metanephrines or 24-hour urinary fractionated metanephrines and catecholamines (essential if symptoms, familial disease, or before surgery).
• Genetic testing for SDHx mutations (SDHD, SDHB and others), whole body imaging (CT or MRI of neck, chest, abdomen and pelvis, or 68Ga-DOTATATE PET-CT) for multicentric disease or multiple paragangliomas.

• Surgical resection is the treatment of choice for tympanicum tumours, with cure rates of 95 to 100 percent. The approach depends on tumour size, with preservation of the facial nerve and ossicles:
  • transcanal (endoscopic or microscopic) approach for small tumours (limited to the promontory, Glasscock-Jackson types I and II)
  • tympanotomy with extended facial recess, mastoidectomy and posterior tympanotomy for larger tumours (types III)
  • combined mastoid neck approach for extensive disease
• Preoperative embolisation (superselective embolisation of the ascending pharyngeal artery feeders, 24 to 48 hours before surgery) is used for larger tumours. Use bipolar cautery and haemostatic agents. Intraoperative blood loss is usually small for small tumours.
• Hearing is preserved in most with ossicular chain repair (ossiculoplasty).
• Radiotherapy: stereotactic radiosurgery (gamma knife 12 to 15 Gy to the margin) or fractionated radiotherapy (45 to 50 Gy in 25 fractions) for patients who are unfit for surgery, for recurrent or residual disease, and for extensive tumours, with tumour control in more than 90 percent over 5 to 10 years (the tumour does not shrink, but stops growing).
• Observation: for elderly or asymptomatic patients with small tumours (wait and scan), with MRI every 6 to 12 months, as growth is slow (about 1 to 2 mm per year) in many; indicated when the risks of surgery or radiotherapy outweigh benefits.
• Management of secretory tumours: alpha adrenergic blockade (phenoxybenzamine 10 mg twice daily increasing by 10 to 20 mg every few days to 20 to 100 mg daily, or doxazosin 2 to 16 mg daily) for 7 to 14 days before surgery, followed by a beta blocker (propranolol 20 to 40 mg three times daily) only after alpha blockade, with volume expansion and salt loading.
• Genetic counselling and screening of relatives (SDHx mutation carriers) with annual biochemical tests and periodic imaging.
• Follow up: clinical examination and imaging (MRI or CT) at 6 and 12 months and then annually for at least 5 years, as recurrence rates are 5 to 10 percent for incomplete removal; lifelong follow up for hereditary cases.
• Complications: facial nerve injury, sensorineural hearing loss, cerebrospinal fluid leak, bleeding, and recurrence.