Superior semicircular canal dehiscence: a new cause of vertigo.

There are many known causes of vertigo, but many cases remain unexplained. Sound-induced, pressure-induced, or positional vertigo caused by bony dehiscence of the superior semicircular canal into the middle cranial fossa is a newly described etiology of vertigo. Three case studies of patients with CT evidence and surgical confirmation of bony dehiscence of the superior semicircular canal with variable presentations are described. The history, symptoms, CT findings, vestibular studies, and method of surgical repair are presented. Two patients had disabling vertigo and one had no vestibular symptoms. All underwent exploration via a middle cranial fossa approach with repair of the dehiscence. The bony dehiscence of the superior semicircular canal of the asymptomatic patient was identified and closed at the time of an encephalocele repair procedure. All patients did well postoperatively and both patients with vertigo improved. Bony dehiscence of the superior semicircular canal may cause vertigo or be asymptomatic and should be added to the differential diagnosis of vertigo.