Glomus tympanicum is a paraganglioma located on the cochlear promontory in the middle ear cavity — the most common middle ear tumor. It originates from paraganglion cells (chemoreceptors). Clinically presents with pulsatile tinnitus and conductive hearing loss. Otoscopy shows a red/bluish vascular mass behind the tympanic membrane. CT shows a well-defined soft tissue mass on the promontory with avid enhancement. NO jugular foramen erosion — this is the most important distinguishing finding from glomus jugulare. Small lesions are completely confined to the middle ear. Salt-and-pepper pattern on MRI may be seen in larger tumors; smaller ones show only an enhancing focus. Functionally inactive (1-3% secrete catecholamines). Multiple paragangliomas may be seen in SDH gene mutation carriers.
Age Range
40-70
Peak Age
55
Gender
Equal
Prevalence
Uncommon
Glomus tympanicum originates from paraganglion cells surrounding Jacobson's nerve (tympanic branch of CN IX) or Arnold's nerve (auricular branch of CN X) along the middle ear mucosa. Paraganglion cells are of neural crest origin and have chemoreceptor function. The tumor grows slowly and is usually benign but may be locally invasive. Due to its intense vascularity, it shows avid enhancement on CT and MRI — the tumor contains a rich capillary network and arteriovenous shunts. In larger tumors, the flow difference between arterial supply and venous drainage creates the 'salt-and-pepper' pattern on MRI: high-flow vessels appear as flow voids (salt = black dots) and tumor tissue as signal (pepper = intermediate-high signal) on T1 and T2. This pattern may not be visible in small glomus tympanicum tumors because vessel diameter remains below MRI resolution. SDH (succinate dehydrogenase) gene mutations (SDHB, SDHC, SDHD) cause hereditary paraganglioma syndrome and increase the risk of multiple tumors.
A well-defined vascular mass rising from the cochlear promontory, seen as a red/bluish retrotympanic mass on otoscopy and a well-defined soft tissue on the promontory on CT. This combination is pathognomonic for glomus tympanicum.
On thin-section HRCT, a well-defined soft tissue density mass (40-60 HU) is seen on the cochlear promontory. The mass is confined within the middle ear cavity and protrudes from the promontory surface. In small lesions (<5mm), it may appear as only mild soft tissue thickening on the promontory. The jugular plate must be intact (otherwise glomus jugulare should be considered). Avid enhancement on contrast CT.
Report Sentence
A soft tissue mass measuring approximately ___mm on the cochlear promontory in the right/left middle ear with avid enhancement is seen, consistent with glomus tympanicum.
The jugular plate (bony covering of the jugular bulb in the temporal bone floor) is intact — this is the most critical distinguishing finding from glomus jugulare. Jugular plate erosion (moth-eaten pattern) is pathognomonic for glomus jugulare. An intact jugular plate confirms the tumor originates from the middle ear paraganglion and simplifies surgical planning.
Report Sentence
The jugular plate is intact with no bone erosion suggestive of glomus jugulare.
On contrast MRI, glomus tympanicum shows avid enhancement. In small tumors (<1cm), it appears as a homogeneously enhancing focus — salt-and-pepper pattern may not be visible. In larger tumors (>1cm), the salt-and-pepper pattern becomes apparent: on T1 and T2, high-flow arteries create flow voids (hypointense dots = salt) while tumor tissue shows intermediate-high signal (pepper). On contrast sequences, tumor parenchyma enhances avidly while flow voids do not.
Report Sentence
An avidly enhancing mass on the promontory is seen on MRI, consistent with paraganglioma.
On arterial phase contrast CT, glomus tympanicum shows very intense enhancement — tumor density may match arterial structures. This finding reflects the hypervascular nature of paragangliomas and is important for differentiation from other pathologies in the same region (effusion, granulation). Addition of arterial phase to temporal bone CT protocol is recommended when paraganglioma is suspected.
Report Sentence
Intense enhancement matching arterial structures is seen in the lesion in the arterial phase, consistent with hypervascular paraganglioma.
On T2-weighted sequences, glomus tympanicum shows hyperintense signal. In larger tumors, flow voids of high-flow vessels on T2 appear as hypointense dots — a component of the salt-and-pepper pattern. The T2 finding may be non-specific but together with flow voids strengthens the paraganglioma diagnosis.
Report Sentence
Hyperintense signal with flow voids is seen in the lesion on T2-weighted sequences, consistent with hypervascular paraganglioma.
Criteria
Small mass on promontory, confined to middle ear.
Distinct Features
Easy surgical excision, low complication, complete resection targeted.
Criteria
Mass completely filling middle ear, extension to mastoid or EAC.
Distinct Features
Surgery more complex, ossicular chain displacement possible.
Criteria
Extension to jugular bulb or carotid canal — now classified as glomus jugulotympanicum.
Distinct Features
Preoperative embolization required, lower cranial nerve involvement possible, multidisciplinary surgery.
Distinguishing Feature
Glomus jugulare has jugular foramen erosion, larger, lower cranial nerves affected; tympanicum has intact jugular plate, localized on promontory
Distinguishing Feature
Cholesteatoma does not enhance, bright on DWI, in Prussak/epitympanum; glomus tympanicum enhances avidly, on promontory
Distinguishing Feature
COM has diffuse opacification, no focal promontory mass; glomus tympanicum is focal promontory mass with avid enhancement
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
12-monthGlomus tympanicum is curatively treated with surgical excision. Transcanal approach is sufficient for small tumors. Preoperative embolization reduces intraoperative bleeding in large tumors. BIOPSY CONTRAINDICATED — risk of massive hemorrhage due to intense vascularity. SDH gene mutation should be screened and whole-body assessment for multiple paragangliomas performed (carotid body, vagal, jugulare). 1-3% may be functional — catecholamine screening should be performed.
Glomus tympanicum is the most common middle ear tumor. Surgical excision is curative. Preoperative angiography/embolization may be needed for large lesions. Whole-body screening for multiple paraganglioma (SDH mutation) should be considered. Biopsy is contraindicated — risk of profuse bleeding.