Fact-sheet: Superior semicircular canal dehiscence
Updated on 04/23/2018 at 9:31 AM
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Definition
Bony dehiscence of the roof of the superior semicircular canal.
Acquired origin due to temporal bone resorption, with a probable genetic predisposition.
Referred to as the "third window" by English-language authors.
Consequence: pressure disturbances of the inner Ear fluids.
In 25% of cases: associated with a more extensive malformation of the petrous bone roof.
Bilateral involvement possible.
Clinical features
Asymptomatic.
Conductive or mixed hearing loss.
Possible vertigo (Tullio phenomenon)
CT
Coronal slices to best assess the dehiscence
Measurement of the bony defect size
Management
Surgical treatment if disabling symptoms: canal plugging and reconstruction of the bony wall