Superior canal dehiscence syndrome (SCDS) was first described by Minor et al. in 1998. Symptoms associated with SCDS include conductive hearing loss and vertiginous symptoms in the setting of loud noises (Tullio phenomenon) or during the Valsalva maneuver. The condition is caused by a bony defect in the roof of the superior semicircular canal. We encountered the case of a 46-year-old male patient with SCDS who presented with pressure- and loud sound-induced vertigo. The patient was diagnosed as having SCDS based on pressure- and sound-induced occurrence of nystagmus confirmed by video-oculography (VOG). We also investigated the prevalence of superior semicircular canal dehiscence at our hospital using our CT scan database. The roof of the superior semicircular canal was classified into three types, normal, thin bony roof, and bony defect. Out of 1003 ears, 897 ears (89.4%) were normal, 77 ears (7.7%) had a thin bony roof, and 29 ears (2.9%) showed a bony defect in the roof of the superior semicircular canal. Out of 25 patients (29 ears) with a bony defect, only one patient was diagnosed as having SCDS.
