Glomus tympanicum paragangliomas (chemodectomas) are the most common middle ear tumor.
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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
Glomus tympanicum paragangliomas arise from the Jacobson nerve at the cochlear promontory.
Radiographic features
CT is usually the best modality to assess these masses.
CT
- 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 tumors
- intact jugular bulb
The Glasscock-Jackson and Fisch classifications of glomus tumors 5 are based on the local extension of the tumor and their effect on mortality and morbidity. Glomus tympanicum paragangliomas are considered type A tumor, 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:
-
glomus jugulare paraganglioma
- permeative destruction of the floor of the middle ear
- involving the jugular foramen
- presents with a dehiscent jugular bulb
-
facial nerve schwannoma
- pedunculated mass arising from the facial nerve
- involving the tympanic segment of the facial nerve
-
congenital cholesteatoma
- no enhancement on post-contrast T1 MRI
