Presentation
History of bilateral chronic suppurative otomastoiditis, presenting with reduced hearing on right side
Patient Data
Axial high resolution bone window images of bilateral temporal bones:
Right temporal bone
- ossification of membranous labyrinth involving all the cochlear turns (complete obliteration of middle and apical turns)
- non-visualization of all the semicircular canals, indicating complete obliteration of the canals by the ossification. Vestibule is spared
- features of chronic otomastoiditis are noted in the form of non-visualized middle ear ossicles, soft tissue opacification of mastoid antrum, retracted tympanic membrane with focal perforation of the posterior aspect of pars flaccida of tympanic membrane
- cochlear and vestibular aqueducts are well seen
These features are suggestive of labyrinthitis ossificans.
Left temporal bone
- fluid opacification of mastoid antrum and epitympanic recess of middle ear cavity with normal appearance of middle ear ossicles, representing chronic oto-mastoiditis
- membranous labyrinth appears normal
- retraction of tympanic membrane is noted
Case Discussion
HRCT temporal bone showed severe degree of ossification of right membranous labyrinth involving both cochlea and semicircular canals with sparing of the vestibule. There were features of chronic oto-mastoiditis on both sides, more severely affecting the right middle ear cavity. Hence, the diagnosis of labyrinthitis ossificans was given.
Labyrinthitis ossificans is a condition characterized ossification of membranous labyrinth to varying degrees, ranging from mild haziness of the lucent labyrinth to complete obliteration. It is usually secondary to prior infection, inflammation or trauma.
MRI and CT are complementary to each other, with MRI being more sensitive in the early pre-ossification stages of labyrinthitis.
Heavily T2-weighted MRI sequence (CISS) of the inner ear can identify intermediate signals in the normally hyperintense inner ear.
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