Superior Canal Dehiscence Syndrome

Superior Canal Dehiscence Syndrome

Superior Canal Dehiscence Syndrome
By Meg Marinis, Director of Medical Research

Imagine being the parent of a child who misdiagnosed their daughter as a paranoid schizophrenic? Absolutely heartbreaking.

But now, imagine being that daughter who no one would believe...

In Episode 622, Shiny Happy People, Ken and Mary May bring in their sixteen-year-old daughter Hayley to the ER after she tried to claw her own eyes out when her parents informed her they were planning to commit her to an institution. Hayley has been previously diagnosed as a paranoid schizophrenic months ago, based on her symptoms and the fact she had a grandfather who also suffered from the disease and killed himself at a young age. Dr. Kevin Fisher, the Seattle Grace-Mercy West Hospital psych resident, needs to have Dr. Alex Karev medically clear Hayley before they take her upstairs to the floor.

But as Hayley repeatedly denies being crazy, begging them to believe her, Alex decides to follow a hunch and run some tests. Little did anyone know that Hayley actually suffered from something that could be fixed with a simple surgery...

So, Superior Canal Dehiscence Syndrome is...?

Superior Canal Dehiscence Syndrome (SCDS) is a rare condition of the ear, which results from an opening ("dehiscence") in the bone overlying the uppermost ("superior") semi-circular canal within the inner ear. With the dehiscence, fluid can be displaced by sound and pressure stimuli. In 1998, Dr. Lloyd Minor of Johns Hopkins University first described the condition, which leads to both hearing and balance disorders. The syndrome is caused by a thinning or complete absence of the part of the temporal bone overlying the superior semicircular canal of the vestibular system either due to slow erosion of the bone or physical trauma to the skull.

Are there other symptoms besides appearing mentally ill?

The main symptom is the loss of hearing, or enhanced hearing of noises transmitted through the bone, giving one the sense that the room is "jumping" at the sound of a loud noise. However, here is a more in-depth list of possible signs and symptoms of the disease...

- Autophony: An afflicted person may be able to hear the sound of their own voice as disturbingly loud and distorted (this type of hearing may be defined as hyperacusis), as if through a "cracked loudspeaker." Also, patients can hear other self-generated noises such as their heartbeat, eye movements, creaking joints, chewing, the sound of their own footsteps, and even digestion.

- The Tullio Phenomenon: This occurrence may be defined as a sound-induced loss of hearing triggered by normal sounds; this feeling presents with the loss of equilibrium, motion sickness, or even actually nausea. Also, the felt presence of involuntary eye movements (also known as nystagmus), sometimes rotational and also set off by sound, gives the impression that the world is tipping on its side.

- Low-Frequency Conductive Hearing Loss: This symptom may be explained by dehiscence acting as a third window. Vibrations entering the ear canal and middle ear abnormally divert through the superior semicircular canal and up into the intracranial space, where they become absorbed instead of being registered as sound in the hearing center, or cochlea.

- Pulsatile Tinnitus: This type of tinnitus (the perception of sound within the ear in the absence of corresponding external sound) comes from the gap in the dehiscent bone allowing the normal pulse-related pressure changes within the cranial cavity to enter the inner ear abnormally. Patients describe this feeling as a "whooshing" noise inside their heads.

- Other symptoms: People diagnosed with SCDS also report vertigo, dizziness, headaches/migraines, fatigue, and brain fog.

How do doctors diagnose SCDS?

The syndrome can be very difficult to diagnose because doctors cannot see the tear in the bone unless they ask for a very specific CT. There is a 30% chance of misdiagnosis, and the disease also remains rarer than others. Doctors must count on characteristic symptoms, a clinical examination, a CT, and findings on vestibular evoked myogenic potentials (VEMP) tests.

And what about treatment?

Some patients only suffer from a mild form of the syndrome and simply try to avoid provocative stimuli (such as loud noises). However, for those who remain debilitated from their symptoms, a surgery may be done. The procedure involves repairing the gap in the temporal bone by resurfacing the affected bone or plugging of the superior semicircular canal. Techniques can be performed by accessing the site of the dehiscence either via a middle fossa craniotomy or via a canal drilled through the transmastoid bone behind the affected ear.

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