Superior Canal Dehiscence Syndrome
 
Superior canal dehiscence syndrome is a balance disorder resulting from a hole in the bone overlying the superior (uppermost) semicircular canal within the inner ear. This abnormal opening affects the vestibulo-ocular reflex (which repositions the eyes to maintain clear vision during head movement) and can cause dizziness, nausea, and vestibular hyperacusis (vertigo and imbalance triggered by sound).

Superior canal dehiscence syndrome is thought to result from a congenital condition in which the bone over the superior canal is thinner than normal and thus more vulnerable to damage from gradual erosion or from forces such as violent coughing or a blow to the head.

The diagnosis of superior canal dehiscence syndrome can be difficult. Bone-imaging studies, such as a CT scan, might not reveal a tear in the bone, if present. Additional tests, such as vestibular evoked myogenic potentials (VEMP), are important for revealing the eye movements evoked by sound and pressure stimuli.

Surgical treatment involves patching the bone from inside the skull. According to the Laboratory of Vestibular Neurophysiology at Johns Hopkins University School of Medicine, this treatment, which is sometimes coupled with physical therapy, has been successful in relieving symptoms.