Semicircular Canal Dehiscence refers to a thinning or disruption of the temporal bone overlying one or more of the semicircular canals, (SSC’s) of the inner ear. This results in the vestibular system becoming sensitive to loud sounds or pressure changes in the inner ear or skull. Manoeuvres that effect pressure and induce vertigo include coughing, sneezing and straining.

Signs and Symptoms

- Vertigo and oscillopsia provoked by loud noises or pressure changes
- Autophony (increased resonance of one’s own voice)
- Hypersensitivity to bone-conducted sounds
- Apparent conductive hearing loss
- Disequilibrium and imbalance

Cause

With a dehiscence of the temporal bone housing the SSC, the fluid in the membranous SSC can be displaced by sound and pressure stimuli. It is thought that SSC dehiscence maybe due to a developmental abnormality. Approximately 1-2% of the population have abnormally thin bone overlying the superior SSC. Disruption of this this layer may occur due to trauma or pressure of the over lying temporal lobe of the brain.

Diagnosis

Audiometry (analysis of hearing), assessment of the eye movements (nystagmus) evoked by sound and pressure stimuli, and VEMP (vestibular-evoked myogenic potentials) testing may have a role in the diagnosis. CT imaging of the temporal bones may reveal the opening in the bone that should be covering the SSC.

Treatment

If the symptoms are severe and the provoking stimuli can’t be avoided, surgical repair of the dehiscence can be required. Best Balance Physiotherapy vestibular rehabilitation can improve gaze stability and disequilibrium whether or not people undergo surgical repair.