ABSTRACT
The association of vertigo or oscillopsia induced by pressure change or loud sounds, with dehiscence of the superior semicircular canal (SSC) was first described in 1998. Dehiscence of otic capsule bone overlying the SSC was identified on computerized tomography (CT). Superior semicircular canal dehiscence (SSCD) syndrome has subsequently become a recognized clinical condition that encompasses a wide variety of vestibular and auditory symptoms. Dehiscence of bone over the SSC and consequent connection with the middle cranial fossa provides a third mobile window into the inner ear in SSCD syndrome (SSCDS). Conversely, inward movement at the dehiscence causes ampullopetal flow towards the ampulla, which is inhibitory and causes tonic downward eye movement and ipsilateral extorsion. Dehiscence alone is not sufficient to cause the syndrome, and many patients have dehiscence but are asymptomatic. Middle fossa craniotomy has the advantage of direct visualization of the dehiscence.
