Operative Management of Superior Semicircular Canal Dehiscence

Abstract

Plugging of the SSCD, while efficacious in alleviating the symptoms of the disease, may cause loss of labyrinthine function beyond the superior canal.

Conductive Hearing Loss Caused by Third-Window Lesions of the Inner Ear

“…Low-frequency (<2,000 Hz) bone conduction thresholds are sometimes at supranormal levels, 0 to −20 dB, or better. The lack of middle ear pathologic findings as a cause for the CHL in SCD has been well documented by a variety of diagnostic tests such as tympanometry, acoustic reflexes, laser Doppler vibrometry, air-conducted VEMP testing, otoacoustic emission (OAE) testing, and by exploration of the middle ear (9)(10)(11)(12)(13)(14)(15)(16). Definitive evidence that the SCD can cause a CHL is demonstrated by resolution of the air-bone gap upon patching or plugging the dehiscence, as has been reported by various investigators (9,12,20,21).…”

“…The lack of middle ear pathologic findings as a cause for the CHL in SCD has been well documented by a variety of diagnostic tests such as tympanometry, acoustic reflexes, laser Doppler vibrometry, air-conducted VEMP testing, otoacoustic emission (OAE) testing, and by exploration of the middle ear (9)(10)(11)(12)(13)(14)(15)(16). Definitive evidence that the SCD can cause a CHL is demonstrated by resolution of the air-bone gap upon patching or plugging the dehiscence, as has been reported by various investigators (9,12,20,21). The mechanism of CHL in an SCD is a combination of an increase in air conduction thresholds combined with an improvement in bone conduction thresholds (11,(17)(18)(19)(20)(21)(22), as described above.…”

“…The report of Minor et al is noteworthy because these patients did not have any features of genetic deafness or apparent malformations of the inner ear, and their clinical presentation was similar to patients with middle ear disease such as otosclerosis. Several authors have now reported CHL as a manifestation of SCD (9)(10)(11)(12)(13)(14)(15)(16). Our research group has conducted a series of studies to investigate the mechanisms by which an SCD results in a CHL (11,(17)(18)(19)(20)(21)(22).…”

Measurements of Human Middle- and Inner-Ear Mechanics With Dehiscence of the Superior Semicircular Canal

“…Definitive proof that the air-bone gap in these patients is indeed the result of the SCD is the closure of the gap when the dehiscence is repaired (3,7). Figure 1A shows a preoperative audiogram from a 35-year-old patient with SCD who presented with both vertigo and an air-bone gap.…”

Trans-mastoid Repair of Superior Semicircular Canal Dehiscence

“…Some authors have also argued that traumatic manipulation or inadvertent suctioning of the membranous labyrinthine and loss of perilymph during dural elevation may contribute toward postoperative sensorineural hearing loss 5 which has been reported in case series to be as high as 30%. 8 As the focus of surgical repair shifts away from canal resurfacing to canal plugging, the transmastoid approach has gained prominence. Several case series of the transmastoid approach to canal plugging have been described in the literature.…”