Concept
The semicircular canal dehiscence (SCD) is a category of rare neurotological diseases/disorders affecting the inner ears, which gathers the superior SCD, lateral SCD and posterior SCD. These SCDs induce SCD syndromes (SCDSs), which define specific sets of hearing and balance symptoms. This entry mainly deals with the superior SCDS. The superior semicircular canal dehiscence syndrome (SSCDS) is a set of hearing and balance symptoms that a rare disease/disorder of the inner ear's superior semicircular canal/duct induces. The symptoms are caused by a thinning or complete absence of the part of the temporal bone overlying the superior semicircular canal of the vestibular system. There is evidence that this rare defect, or susceptibility, is congenital. There are also numerous cases of symptoms arising after physical trauma to the head. It was first described in 1998 by Lloyd B. Minor of Johns Hopkins University in Baltimore. The superior canal dehiscence can affect both hearing and balance to different extents in different people. Symptoms of the SCDS include: Autophony – person's own speech or other self-generated noises (e.g. heartbeat, eye movements, creaking joints, chewing) are heard unusually loudly in the affected ear Dizziness/vertigo chronic disequilibrium caused by the dysfunction of the superior semicircular canal Tullio phenomenon – sound-induced vertigo, disequilibrium or dizziness, nystagmus and oscillopsia Pulse-synchronous oscillopsia Hyperacusis – the over-sensitivity to sound Low-frequency conductive hearing loss A feeling of fullness in the affected ear Brain fog Fatigue Headache/migraine Tinnitus – high pitched ringing in the ear SCDS-related autophony differs greatly in quality and range from the more common form which results from an open, or patulous Eustachian tube through which sufferers of this disorder hear the sound of their own voice and breathing. In contrast, patients with SCDS-related autophony report hearing their own voice as a disturbingly loud and distorted "kazoo-like" sound deep inside the head as if relayed through "a cracked loudspeaker.
