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Glomus tympanicum is a benign, slow-growing paraganglioma arising from paraganglionic cells along the tympanic branch of the glossopharyngeal nerve (Jacobson's nerve), located in the middle ear cavity, typically on the cochlear promontory.

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It is the most common primary neoplasm of the middle ear.

Epidemiology

• More common in middle-aged women
• Usually unilateral, though bilateral forms occur in familial syndromes (e.g., SDHx mutations)
• Represents a nonchromaffin paraganglioma — rarely secretes catecholamines

Etiopathogenesis

Anatomy & Origin

• Arises from paraganglionic tissue on the promontory of the cochlea
• Confined to the middle ear cavity, but may grow into:
  • Hypotympanum
  • Eustachian tube
  • Rarely into the mastoid or internal auditory canal

Clinical Features

• Pulsatile tinnitus (classic symptom)
• Conductive hearing loss
• Aural fullness
• Red retrotympanic mass on otoscopy
• No pain or facial nerve dysfunction unless large

Radiology