Radiologically-proven New Development of Superior Semicircular Canal Dehiscence Associated With Development of Superior Semicircular Canal Dehiscence Syndrome

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This report describes a case of development of radiologic superior semicircular canal dehiscence and reviews the literature for pertinent clinical and radiologic findings in patients with superior semicircular canal dehiscence syndrome (SCDS). A 28-year-old man presented with auditory and vestibular symptoms of SCDS and underwent a high-resolution temporal bone computed tomography scan that showed frank dehiscence of the right superior semicircular canal. Diagnosis of SCDS was further verified with audiometric and cervical vestibular-evoked myogenic potential (cVEMP) thresholds. The patient had previously undergone a computed tomography scan 12 years prior for work-up of sudden sensorineural hearing loss that showed no evidence of superior semicircular canal dehiscence bilaterally. A combination of diagnostic and therapeutic interventions was conducted consisting of preoperative audiometric and cVEMP thresholds, followed by middle fossa craniotomy for surgical repair of the dehiscence. Postoperative audiometric and cVEMP thresholds and symptomatic improvement of SCDS after surgical repair of the dehiscence. The patient reported resolution of his clinical symptoms after surgical repair of the dehiscence. Postoperative cVEMP thresholds improved to the normal range and the mild low-frequency conductive hearing loss resolved. To our knowledge, this case report is the first description of radiologically proven new development of superior canal dehiscence. Further prospective studies that include serial imaging examinations may help with visualizing and understanding the temporal evolution of superior canal dehiscence, and better elucidate the relationship between development/ progression of superior canal dehiscence and onset of clinical symptoms.