Third window syndrome represents a group of symptoms that result from a pathological communication between the inner ear and the surrounding structures, these symptoms include auditory symptoms including bone conducted hyperacusis, autophony or pulsatile tinnitus, vestibular symptoms include sound or pressure induced vertigo or chronic imbalance.

The diagnosis of third mobile window syndrome depends on the presence of typical symptoms, specific VEMP or other findings in some audio vestibular tests, and it is confirmed by high resolution Temporal bone CT scan.

Superior semicircular canal dehiscence is the first and most commonly known type of third window disease, however other types were discovered later on, including posterior semicircular canal dehiscence, cochlear- facial nerve dehiscence, vestibular aqueduct- Jugular bulb dehiscence and enlarged vestibular aqueduct.

A new type of third window syndrome was discovered in our center, and to the best of our knowledge it was never been described in the literature, which is vestibular aqueduct dehiscence with hyperpneumonized air cells.