mercoledì 30 dicembre 2009

Labyrinthine ossificans


On the left, there is severe ossification and encroachment of the cochlea with extension to the vestibule and semicircular canals, which are also severely involved. The cochlear aqueduct is slightly stenotic. On the right, there is peripheral osseous hyper density of the cochlea with mild encroachment.

Differential diagnosis:
- Labyrinthine ossificans
- Cochlear aplasia
- Intravestibular schwannoma
- Cochlear otosclerosis
- Labyrinthine schwannoma

Diagnosis: Labyrinthine ossificans

Key points

Most common cause of acquired childhood deafness
Most common clinical presentation – bilateral sensorineural hearing loss 2-18 months after meningitis
May also occur after other infectious, inflammatory, trauma, or surgery
After meningitis or hematogenous infection – bilateral
After otitis media – unilateral
Rarely – severe vertigo
Suppurative membranous labyrinthitis starts inflammatory cascade which leads to fibrosis and eventually ossification
Dedicated IAC/temporal bone CT best for detection
Mild – mild increased haziness in the fluid spaces of the membranous labyrinth and prominent modiolus
Severe – complete obliteration of the membranous labyrinth with bony replacement of the fluid spaces
On MR, low signal bone encroaches (mild) or obliterates (severe), high signal fluid spaces of the membranous labyrinth
Importance – must identify cochlear labyrinthitis ossificans before cochlear implant so that it may be surgically treated
Treatment – cochlear implant, or labyrinthectomy for severe vertigo

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