Third Window Syndrome

Ninety years ago, Tullio described the physiologic outcomes of creating a third mobile window in the semicircular canals of pigeons. Since that time, many locations of third mobile windows have been described; however, the sound-induced dizziness and/or nystagmus has been memorialized by the eponym ‘Tullio phenomenon.’ Clinically, the most thoroughly characterized third mobile window is superior semicircular canal dehiscence. In 1998, Minor and coworkers first reported the diagnosis of CT positive superior semicircular canal dehiscence. Minor later reported a conductive hearing loss, which was recognized as a pseudoconductive hearing loss (bone-conduction hyperacusis), as well as a reduced cervical vestibular myogenic potential (cVEMP) threshold in patients with superior semicircular canal dehiscence. While superior semicircular canal dehiscence is well-recognized; it has been reported the existence of a CT negative third window syndrome with the same clinical phenotype of superior semicircular canal dehiscence exists. It has been reported that CT negative third window syndrome is associated with a pseudoconductive hearing loss and an abnormally reduced cVEMP threshold, among other objective findings typically found in superior semicircular canal dehiscence patients.

The more general term of third window syndrome has gained acceptance because the same spectrum of symptoms, signs on physical examination and audiological diagnostic findings are encountered with superior semicircular canal dehiscence, cochlea-facial nerve dehiscence, cochlea-internal carotid artery dehiscence, cochlea-internal auditory canal dehiscence, lateral semicircular canal-superior semicircular canal ampulla dehiscence, modiolus, “perilymph fistula,”posterior semicircular canal dehiscence, posterior semicircular canal-jugular bulb dehiscence, superior semicircular canal dehiscence-subarcuate artery dehiscence, superior semicircular canal dehiscence-superior petrosal vein dehiscence, vestibule-middle ear dehiscence, lateral semicircular canal-facial nerve dehiscence, wide vestibular aqueduct in children, posttraumatic hypermobile stapes footplate and in patients with CT negative third window syndrome. A common structural finding in all of these conditions is an otic capsule defect that creates a ‘third window.’

Over the past 60 years, we have learned much regarding the clinical features, outcomes measured by validated survey instruments and neuropsychology testing as well as objective diagnostic studies in third window syndrome. Beyond the hallmark symptoms of sound-induced otolithic dysfunction (dizziness) and autophony, a wide range of other associated clinical manifestations have been reported, including: cognitive dysfunction, spatial disorientation, anxiety and migraine.

Overall, we are confident that this Research Topic in vestibular science and disease will provide important insights to both scientists and clinicians who deal with these fascinating areas of peripheral vestibular dysfunction and associated pathophysiology.

For this Research Topic, we aim to bring together recent discoveries of the mechanisms of the associated spectrum of symptoms, dysfunction, novel diagnostic tools and interventions to resolve third window syndrome. We are interested in receiving manuscripts detailing the clinical features, novel approaches in diagnostic testing, medical and surgical management, systematic reviews, other associated diseases, the sequelae of third windows, and the outcomes of intervention across the spectrum of third window syndrome. Clinical studies and basic studies utilizing animal models will be welcome.