Semicircular canal dehiscence
Dehiscence of the semicircular canals has been described for all three of the canals, namely superior, posterior and lateral. The presence of dehiscence does not mean that an individual will experience any symptoms. Indeed in a large study, 10% of the CT scans of the temporal bone showed dehiscence of the superior semicircular canal in patients who lacked the typical symptoms of the associated syndrome .
In some patients dehiscence of both the superior and posterior semicircular canals has been found, raising the possibility that the pathogenesis relates to abnormal bony development. Alternatively/additionally it may be due to the proximity of these two canals to the jugular bulb (the lateral canal is not adjacent to it).
Dehiscence of the semicircular canal forms a "third window" into the inner ear, in addition to the round and oval windows. This allows movement of the endolymph to be induced by sound and pressure stimuli and may result in vestibular and auditory symptoms.
Treatment and prognosis
Surgical closure of the dehiscence has been successful in some cases .