What Is Canal Dehiscence Syndrome?
Canal dehiscence syndrome (also called superior semicircular canal dehiscence syndrome, or SSCD) is a disorder that affects your balance and hearing.
"Dehiscence" is another word for hole or a tear or opening that forms. Generally, it is due to the way the inner ear forms in utero. If you have SSCD, you have a hole or a very thin place in the bone in your ear that helps your body balance itself. It also can cause problems with the way sound comes into your ear.
SSCD is a rare condition. Only 1%-2% of the population has been diagnosed with it. Not everyone with the syndrome has symptoms, so the number of people who have it could be slightly higher.
It affects men and women equally. People usually discover they have it in their 40s.
Canal Dehiscence Syndrome Symptoms
When you have SSCD, you might have one or more of the following:
- Echoes of sounds in your ear, like when you eat or talk (called autophony)
- Fullness in your ears
- Hearing loss (learn more about the different types of hearing loss, including low-frequency hearing loss.)
- Internal noises, like your heartbeat, that are louder than normal
- Quick side to side or up and down movements of your eyes (called nystagmus)
- Ringing in your ears
- Sound of your pulse in your ears
- A feeling that things are moving when they aren’t (called oscillopsia)
- Vertigo or dizziness
These symptoms can be triggered when you:
Canal Dehiscence Syndrome Causes
Three small looped structures inside your ear called semicircular canals have fluid in them that moves when you move. When the fluid moves, tiny hairs inside the canals also move. This tells your brain how your body is positioned. Your brain takes that information and tells your muscles how to act to help you keep your balance. Further reading: Everything you need to know about hearing loss and balance.
The canal that sits highest in your ear, the superior semicircular canal, is covered by bone. When you have SSCD, this bone has a hole or very thin place in it. This affects how the sensors react to movement.
A few things can cause SSCD, including:
- A gene passed down from your parents that kept the bone in that area from growing thick enough
- An infectious disease
- Some form of trauma that damaged the bone
You can get SSCD in either ear. Some people have it in both. When that's the case, one ear typically causes more symptoms than the other.
Canal Dehiscence Syndrome Diagnosis
Your doctor will do an exam and ask questions about your symptoms and when you have them. They may want to do a test called a videonystagmography (VNG). This test measures your eye movements in order to look for signs of a problem with your sense of balance.
You’ll be asked to wear goggles that will record your eye movements.
You'll follow targets with your eyes, and the person doing the exam may put your head in different positions. They also might use air or water to change the temperature slightly in your ear canal. You might feel your eyes make some jerky movements for a short time.
After the VNG, your doctor also may want you to have a test called a vestibular evoked myogenic potentials (VEMP) test. It checks the reflex in a muscle in your neck that responds to sound.
An electrode is placed on the muscle. Then you'll hear low to mid-range tones in one ear while your doctor watches the results on a monitor.
If your doctor suspects you have SSCD, they may order a CT scan of your ear to look for holes in the bone above your canals. This type of scan uses X-rays taken from different angles to show a more complete picture of your ear.
Canal Dehiscence Syndrome Treatment
If your symptoms are minor, you may be able to simply avoid triggers, such as loud noises or altitude changes. If you have hearing loss as a result of your SSCD, your doctor may suggest hearing aids.
If some symptoms are severe -- like oscillopsia, balance issues, or autophony -- your doctor may suggest surgery. The most common surgery used to treat SSCD is called middle cranial fossa approach. A doctor takes some of your tissue or a small piece of bone from your skull and plugs the hole.
A newer procedure, called the transmastoid approach, restores the normal flow of acoustic energy to the cochlea. Recovery time is faster.