Contributors: Jacob B. Hunter, Reid C. Thompson and David S. Haynes
Superior semicircular canal dehiscence (SCD) is a condition in which the bone overlying the superior semicircular canal is absent. The clinical presentation of SCD is highly variable and may include both auditory and vestibular manifestations. The more common symptoms include autophony, sound or pressure induced vertigo, hypersensitivity to sound, and low frequency conductive hearing loss. Repair can be accomplished via either transmastoid or middle fossa approaches, with numerous materials used to either plug or resurface the canal. Herein, we describe our resurfacing technique using a loose areolar tissue-bone pâté-loose areolar tissue sandwich through a middle fossa approach.
Patients with symptomatic SCD not controlled with conservative measures are candidates for repair.
Bleeding disorders should be optimized prior to surgery and patients should hold all anticoagulant medications for at least 1 week prior to surgery.
The patient is positioned in the park bench position and the head is placed in a Mayfield skull clamp.
The diagnosis of SCD is made radiographically, therefore all patients should undergo fine cut temporal bone computed tomography (CT) imaging. In addition, a complete history, physical examination and routine audiometric testing should be performed. While balance function testing is not required, we recommend such testing particularly in patients with vestibular complaints. Vestibular evoked myogenic potentials (VEMPs) can aid in the diagnosis of SCD.
In the coronal plane, the superior semicircular canal is usually located at the level of the posterior external auditory canal. Along the middle fossa floor, the superior semicircular canal is oriented perpendicularly to the posterior petrous ridge. Although the arcuate eminence corresponds to the location of the superior semicircular canal in the majority of patients, this relationship is not absolute. Furthermore, in patients with SCD, the arcuate eminence will likely not be as prominent. In relation to the lateral cortex of the temporal squama, the superior semicircular canal lies roughly 2.5 cm medially.