[Superior-canal dehiscence syndrome].
Superior-canal dehiscence syndrome (SCDS) was first described in 1998; it manifests as symptoms of dizziness and oscillopsia when a sound or pressure stimulus is given to the ear concerned. SCDS is caused by dehiscence ofpetrosal bone overlying the superior, vertical semicircular canal, creating a 'third mobile window' to the labyrinth, in addition to the oval and round windows. Characteristic for this syndrome are eye movements with a vertical-torsion direction, evoked by sound stimuli, or pressure changes via the external ear canal and the Valsalva manoeuvre. The anomaly of the bony structure is visible on a CT scan. With its specific symptoms and characteristics, SCDS is an abnormality of the vestibular system that is relatively easy to diagnose. The syndrome may be treated with conservative or surgical means.