What is Superior Semicircular Canal Dehiscence?
Superior Semicircular Canal Dehiscence
Superior semicircular canal dehiscence (SSCD) is a condition in which there is an opening in the bone covering one of the balance canals of the inner ear. Your inner ear contains fluid-filled tubes called semicircular canals, which are encased in bone. The bone over the superior canal can wear thin or develop a small hole, called a dehiscence. This creates an abnormal “third window” that lets sound and pressure meant for the hearing system reach the balance system. That pressure can cause many of the symptoms of SSCD, such as vertigo, a false sense of motion, and unusually amplified hearing.
SSCD should be diagnosed and managed with an ear, nose and throat specialist or neurotologist. Get medical care right away if you have sudden hearing loss, or sudden severe dizziness with weakness, numbness, trouble speaking or double vision.
How Common Is SSCD?
Symptoms often begin in a person’s mid-40s. About 1% to 2% of people have unusually thin bone over the superior canal. But the link between thin bone and symptoms isn’t straightforward. Some people with thin or open bone on a CT scan have no symptoms, while others have symptoms but no clear opening on imaging.
SSCD becomes more common with age, which suggests it is more often acquired over time than present from birth (1).
What Are the Symptoms of SSCD?
The main symptom of SSCD is vertigo, often triggered by loud sounds (called the Tullio phenomenon) or by pressure on or in the ear (called Hennebert sign) (2). Oscillopsia, where still objects seem to move or bounce, is also common. Other symptoms can include a whooshing sound in the ear in time with your pulse (pulsatile tinnitus) or ringing in the ears. Some people have autophony, where their own voice sounds extremely loud or distorted. Many everyday sounds can seem amplified, so chewing may be uncomfortably loud, and some people can even hear their eyes move or their footsteps. These symptoms can be intrusive, distressing and anxiety-provoking (3).
How Does the Vestibular System Work?
Your inner ear contains a set of fluid-filled canals encased in bone, called the vestibular labyrinth. The semicircular canals contain specialized hair cells. When your head turns, the fluid inside lags behind for a moment because of inertia. This bends the hair cells, which activate the vestibular nerve and send signals to the brainstem, cerebellum and brain. These signals help your brain sense how your head is moving and where it is in relation to your body and gravity.
There are three canals on each side: the superior, lateral and posterior canals. They are sensitive to pressure and need solid bony support to work properly.
The bone over the top of the superior canal is naturally very thin, which makes it vulnerable to injury and erosion. Normally, the balance canals are sealed off from sound vibrations. The fluid in the canals moves only when your head turns, and that movement is how your brain senses head rotation.
In SSCD, pressure changes from the hearing part of the inner ear, the cochlea, can reach the balance canals. Pressure coming from the middle ear is partly transferred into the canal system. This moves the fluid and stimulates the canal, telling your brain your head is moving when it isn’t. This false sense of motion causes the vertigo and dizziness most often linked to SSCD (4).
What Causes SSCD?
Several causes of SSCD are recognized. Some people may be born with thin bone over the canal, with symptoms often starting in early adulthood. In about one-third of these cases, both ears are affected (5).
SSCD can also be acquired over time. Researchers believe the thin bone can gradually wear away from normal pressure and pulsations of the surrounding fluids and structures, or from repeated minor stresses on the skull (6).
Head injuries and skull base trauma, such as from car crashes, are also a recognized cause of SSCD, and SSCD has been linked to head injuries from combat sports (2).
How Is SSCD Usually Treated?
SSCD is diagnosed by a medical provider, usually with a high-resolution CT scan and specialized hearing and balance tests. If symptoms are mild, conservative care is often the best option. This may include avoiding triggers and vestibular therapy. When symptoms are severe, surgery to repair or plug the opening may be recommended. Surgery is generally safe and effective (7), and many people describe feeling that the world has finally stopped moving. No surgery is 100% effective, though, and success varies with the procedure and the surgeon. Some people’s symptoms come back later or don’t fully go away (6).
How the NeuroRescue Program Can Help
Our care is designed to work alongside your ear, nose and throat specialist, neurotologist and other providers, never in place of them.
SSCD is a relatively rare condition, and we regularly work with people living with it. When symptoms are severe, our care focuses on helping you manage symptoms while you wait for surgery. After you’ve recovered from surgery, our focus shifts to helping your brain reintegrate inner ear signals with your vision and body-position sense. When symptoms are milder or surgery isn’t recommended, we focus on therapies that integrate your visual, vestibular and body-position systems, with the goal of improving your balance and stability and reducing oscillopsia.
One challenge with SSCD is that the brain gradually adapts to the faulty inner ear signals and treats them as the new normal. SSCD can be hard to diagnose, and many people struggle with vertigo and nausea for years and see many providers before getting the right diagnosis. By then, the brain has learned to partly compensate. The brain and cerebellum are remarkably good at adapting to changes in inner ear input. But once the opening is surgically repaired, those old adaptations may no longer fit, and they can create problems of their own. Many people notice a big improvement after surgery, but some continue to have dizziness, nausea, balance problems or trouble thinking afterward. Our care is designed to address these remaining problems by helping the brain readjust to the new signals coming from the repaired ear.
Depending on your needs and test results, your program may include exercises to retrain how your eyes and inner ear work together during head movement (8); eye exercises to improve visual stability (9); non-invasive electrical stimulation of the vestibular system through the skin (10); visual stimulation exercises (11), including visual stimulation combined with head movements (12); and exercises in a virtual reality environment (13). Transcranial magnetic stimulation (TMS) has also been studied for chronic dizziness (14). At our clinic, TMS is provided by our psychiatric mental health nurse practitioner, who will evaluate whether it may be appropriate for you. The therapies we recommend are always chosen based on your testing and exam findings. No two NeuroRescue Programs are alike.
How the NeuroRescue Program Works
Your NeuroRescue Program begins with your Discovery Day. We start with a detailed history of your condition and your life on a timeline. This helps us understand the factors that may have contributed to where you are now, and identify related conditions that may be making it harder to move forward.
We measure how your visual, vestibular and balance systems are working through computerized analysis of your eye movements, inner ear reflexes and balance under different conditions. Our testing includes videonystagmography and saccadometry to measure several types of eye movements, the video head impulse test to measure how each semicircular canal is working, and CAPS computerized posturography to assess your balance under different sensory conditions. We also use NeuroSensoryMotor Integration testing to evaluate hand-eye coordination and cognition, and Virtualis testing to assess dynamic eye tracking and your perception of vertical in a virtual reality environment.
We combine this with a thorough physical and neurological exam of your sensory, motor, autonomic and cognitive systems. We also review any relevant lab work, imaging and prior testing, and integrate it with our findings.
Together, this helps us understand which parts of your nervous system are working well, which are struggling, and how quickly they tire. We use that information to design your personal NeuroRescue Program, aimed at improving function in the systems that need support and helping them work together. Our testing also helps us decide when to push and when to let you rest.
Our goal is to help your brain make sense of the signals from your inner ear again, so the world can feel steady and you can move through your day with more confidence.
Your Next Step
Living with SSCD can be disorienting and isolating, especially when it takes years to get answers. You don’t have to keep figuring it out alone. To find out if the NeuroRescue Program is right for you, contact one of our patient care coordinators to schedule your Discovery Day.
It’s never too late to take the next step.
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