Latent superior canal dehiscence syndrome unmasked by stapedotomy for otosclerosis.

OBJECTIVE: This report describes a novel case in which superior canal dehiscence syndrome was unmasked by successful stapes surgery for otosclerosis.
METHODS: Case report and literature review regarding superior canal dehiscence syndrome.
INTRODUCTION: Superior canal dehiscence syndrome is a rare but well described condition in which audiovestibular symptoms are caused by noise or straining. A dehiscence of the superior semicircular canal in the floor of the middle cranial fossa is responsible, and acts as a 'third window' into the inner ear. CASE HISTORY: A patient with confirmed otosclerosis underwent second-side stapedotomy, with good audiometric outcomes. Unfortunately, surgery was complicated by immediate post-operative vertigo and persistent auditory symptoms. A diagnosis of superior canal dehiscence syndrome was eventually made, on the basis of low threshold vestibular evoked myogenic potentials and characteristic computed tomography findings. Superior canal resurfacing resulted in complete resolution of symptoms. DISCUSSION: The otosclerotic focus in the oval window prevented the development of symptoms from this patient's superior canal dehiscence syndrome. Surgical stapedotomy created a third window and resulted in immediate post-operative imbalance and auditory symptoms.
CONCLUSION: The diagnosis of superior canal dehiscence syndrome should be considered in patients with persistent audiovestibular symptoms after stapes surgery. High resolution computed tomography of the temporal bone and vestibular evoked myogenic potential testing, if available, are the investigations of choice in confirming the diagnosis.