Third Mobile Window Syndrome of the Inner Ear: Superior Semicircular Canal Dehiscence and Associated Disorders

Review by A Banerjee
Middlesbrough, UK

I first became interested in superior semicircular canal dehiscence (SCD) syndrome (SSCD) during my fellowship in Perth, Western Australia in 2003. The cohort of patients with SCD were serendipitously identified as a neurologist in the hospital routinely documented Tullio phenomenon in his history along with reduced VEMPs. Thus, a group of patients who had had no definitive diagnosis now had an explanation for their rather unusual set of symptoms and even treatment if their symptoms were severe enough.

Lloyd Minor is synonymous with SCD but it was interesting to note that one of the editors, GJG, performed his first SCD surgery two months before Minor published his case series, having independently identified the condition! I can only imagine what a let down it must have been once he realised that he wasn’t the first person to recognise SCD.

This book with multiple authors is over 500 pages and is in 5 sections:

  • Understanding the third mobile window syndrome
  • Diagnosis
  • Treatment
  • Special situations
  • The patient perspective
  • Future research

The first section details the known sites creating a third mobile window; 18 different entities or their combinations! The development of an experimental model for the various sites gives a better insight into the role the peripheral vestibular syndrome plays in disrupting central nervous system processing. The other chapters in this section cover the uncertainties of the aetiology of this condition, the pathophysiology, a classification and the cognitive/psychological effects of the third mobile window syndrome.

The second section covers the taking of a comprehensive patient history, diagnostic testing and imaging which is described as the ‘three pillars of diagnosis’. There is an excellent section on the basic audiovestibular physiology relevant to the diagnostic testing for SSCD. The imaging section is quite basic and has no great insights.

The treatment section is necessarily short with occlusion and repair/capping. I disagree with their statement that round window reinforcement has been relatively unsuccessful in the treatment of autophony, as this does not correlate with my personal surgical experience in treating patients with SCD related hyperacusis. The treatment of vestibular aqueduct:jugular bulb dehiscence with endovascular therapy in collaboration with the interventional radiologist is an interesting modality of treatment that I had not come across before.

The sections on special considerations and patient experiences are interesting, but do add to the 500+ pages that this book extends to.

When an otologic symptom complex does not fit a diagnosis, it usually gets diagnosed as anxiety or panic. Prior to 1998, SCD patients were routinely misdiagnosed with anxiety or a variety of other disorders. While our recognition of SCD has improved considerably over the last 25 years, the lesser known TMWD patients are suffering the same fate as SCD patients in the 1990s. This book will raise awareness of TMWD as a diagnostic category which includes many entities.

Amazon Link: Third Mobile Window Syndrome of the Inner Ear: Superior Semicircular Canal Dehiscence and Associated Disorders
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