Superior canal dehiscence

Superior canal dehiscence (SSCD) is a very rare medical condition, first described in 1998 by Lloyd Minor of Johns Hopkins University, causing hypersensitivity to sound in those affected. It is caused by a thinning or absence of the temporal bone overlying the superior semicircular canal of the inner ear. This is thought to result from physical trauma to the skull although there is also some evidence that the defect or susceptibility is congenital. It can be detected by computed tomographic scanning of the affected area of the skull, currently the only reliable way to distinguish SSCD from Meniere's disease Once diagnosed, the break can be repaired by surgical resurfacing of the affected bone or plugging of the superior semicircular canal.

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Symptoms

Superior canal dehiscence can affect both hearing and balance, to different extents in different patients.

• autophony: person's own speech or other self-generated noises (e.g. heartbeat, eye movements) are heard louder than normal
• dizziness/vertigo: often aggravated by loud noises
• Tullio phenomenon - nystagmus caused by sounds of a certain pitch and/or volume in the affected ear and/or pressure changes
• Pulse-synchronous oscillopsia
• Low-frequency conductive hearing loss
• In some cases SSCD cause a chronic loss of equilibrium.
• A feeling of fullness in the affected ear
• Tinnitus