Tympanic paragangliomas (previously known as glomus tympanicum tumours) are the most common middle ear tumours.
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Terminology
The term "glomus" was historically used to describe certain types of neuroendocrine tumours arising from paraganglia. The term is, however, imprecise and can be confused with the glomus bodies and tumours that arise from them. It can also be mixed up with glomus tumours of the subcutaneous skin, also referred to as glomangioma.
Epidemiology
There is a female predominance (M: F = 1:3); presentation is most common when patients are more than 40 years old 1,2.
Clinical presentation
May be incidental but symptomatic masses produce pulsatile tinnitus, otalgia, or conductive hearing loss 1,3.
Pathology
Tympanic paragangliomas arise from the Jacobson nerve at the cochlear promontory.
Radiographic features
CT is usually the best modality to assess these masses.
CT
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soft tissue mass lateral to the cochlear promontory
if large may fill the middle ear cavity, and invade the Eustachian tube or mastoid
ossicles may or not be destroyed and may simply be encased
surrounding bony destruction may be present in aggressive tumours
intact jugular bulb
The Glasscock-Jackson and Fisch classifications of paragangliomas 5 are based on the local extension of the tumour and their effect on mortality and morbidity. Tympanic paragangliomas are considered type A tumour, as they are limited to the middle ear cavity.
Treatment and prognosis
Surgical resection is the treatment of choice 4.
Differential diagnosis
On imaging consider:
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permeative destruction of the floor of the middle ear
involving the jugular foramen
presents with a dehiscent jugular bulb
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pedunculated mass arising from the facial nerve
involving the tympanic segment of the facial nerve
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no enhancement on post-contrast T1 MRI
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