A 46-year-old woman presents with unilateral pulsatile tinnitus and conductive hearing loss. Otoscopy shows a reddish mass behind an intact tympanic membrane that blanches when pneumatic pressure is applied (Brown sign). The tumour most commonly arises from paraganglia associated with which structure?
- A The greater superficial petrosal nerve at the geniculate ganglion
- B Arnold's nerve in the floor of the external auditory canal
- C Jacobson's nerve on the cochlear promontory ✓
- D The auriculotemporal nerve in the squamous part of the temporal bone
Correct answer: C. Jacobson's nerve on the cochlear promontory
Explanation
Glomus tympanicum tumours arise from paraganglia situated along the tympanic branch of the glossopharyngeal nerve (Jacobson's nerve), which courses over the cochlear promontory in the middle ear. Brown sign, blanching of the mass with positive pneumatic pressure, supports the diagnosis. Arnold's nerve is the auricular branch of the vagus and supplies cutaneous sensation of the canal wall and concha, not paraganglia within the tympanic cavity, so it kills the best distractor.
Reference: Cummings Otolaryngology Head and Neck Surgery, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.