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Glomus Tympanicum

Summary

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  • Rare, benign paraganglioma arising from glomus bodies in the middle ear
  • Typically presents with pulsatile tinnitus and conductive hearing loss
  • Characteristic "salt and pepper" appearance on CT and MRI imaging

Pathophysiology

  • Originates from paraganglionic tissue in the middle ear
  • Arises from glomus bodies along the tympanic branch of the glossopharyngeal nerve (Jacobson's nerve)
  • Highly vascular tumour with slow growth rate
  • Rarely malignant (<5% cases)

Demographics

  • Most common middle ear tumour
  • Peak incidence in 5th-6th decades of life
  • Female predominance (4:1 female to male ratio)
  • Bilateral in 3-10% of cases
  • Familial occurrence in 10% of cases, associated with mutations in SDH genes

Diagnosis

  • Clinical presentation:
    • Pulsatile tinnitus (most common symptom)
    • Conductive hearing loss
    • Aural fullness
    • Otalgia
  • Physical examination:
    • Red, pulsatile mass behind tympanic membrane
    • Brown's sign: blanching of mass with pneumatic otoscopy
  • Audiometry:
    • Conductive hearing loss
  • Angiography:
    • Tumour blush and feeding vessels

Imaging

  • CT:
    • Soft tissue mass in middle ear
    • Bone erosion of promontory and ossicles
    • "Salt and pepper" appearance due to flow voids
  • MRI:
    • T1: isointense to brain
    • T2: hyperintense with flow voids ("salt and pepper" appearance)
    • Intense enhancement with gadolinium
    • "Flow voids" on T2-weighted images
  • Angiography:
    • Tumour blush
    • Feeding vessels (usually from external carotid artery)

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  • 60-year-old patient presented with left sided pulsatile tinnitus.
  • Cone beam CT showed a 3 mm nodule interposed between the hypotympanic jugular bulb and the caudal aspect of pars tensa.
  • A gloums tumour was confirmed following resection.

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  • A 70-year-old patient presented with right sided pulsatile tinnitus.
  • Otoscopy revealed a dark lesion associated with the tympanic lesion.
  • MRI showed an avidely enhancing lesion deep to the tympanic membrane extending into the hypotympanum.
  • Ga-DOTATATE PET showed high avidity in the lesion, consistent with a glomus tumour.

Treatment

  • Management options:

    1. Observation (for small, asymptomatic tumours)
    2. Surgery (primary treatment modality)
    3. Radiotherapy (for residual tumour or inoperable cases)
    4. Embolization (pre-operative to reduce bleeding)

  • Surgical approaches:

    • Transcanal approach for small tumours
    • Transmastoid approach for larger tumours
    • Infratemporal fossa approach for extensive tumours

  • Complications of treatment:

    • Facial nerve injury
    • Hearing loss
    • CSF leak
    • Vascular injury

  • Follow-up:

    • Regular imaging to monitor for recurrence
    • Long-term follow-up recommended due to slow growth rate

Differential diagnosis

Differential Diagnosis Differentiating Feature
Cholesteatoma Typically appears as a non-enhancing soft tissue mass on CT/MRI
Paraganglioma Usually larger and more vascular, may extend beyond middle ear
Aberrant internal carotid artery Pulsatile mass, no enhancement on contrast imaging
Middle ear adenoma Lacks the characteristic "salt and pepper" appearance on MRI
Facial nerve schwannoma Follows the course of the facial nerve, often involves geniculate ganglion
Jugular foramen schwannoma Originates in jugular foramen, extends into middle ear secondarily
Meningioma Typically arises from middle cranial fossa dura, extends into middle ear
Metastatic tumour Irregular borders with bone destruction; no "salt and pepper" appearance on MRI; no pulsatile flow voids
Chronic otitis media Lacks enhancement on imaging, associated with inflammatory changes
High jugular bulb Non-enhancing vascular structure on imaging, no soft tissue component