Superior Semicircular Canal Dehiscence

What is superior semicircular canal dehiscence?

Superior semicircular canal dehiscence is a condition of the inner ear in which the thin layer of bone that normally covers one of the balance canals is missing or extremely thin. The word dehiscence means an opening or gap. The superior semicircular canal is one of three small, fluid-filled loops inside each ear that sense head movement and help you keep your balance. It sits closest to the brain, directly beneath the floor of the skull.

Normally, the inner ear is a closed system with only two flexible openings, called windows, that let sound energy in and out. When the bone over the superior canal is missing, a so-called third window is created. Sound and pressure that should travel to the hearing organ can escape through this extra opening and stimulate the balance system instead. This is why people with the condition may feel dizzy in response to loud sounds or pressure changes, and may hear internal body sounds unusually loudly.

The condition was first described in the late 1990s, so it is relatively newly recognized. It is considered uncommon, although the exact number of people affected is not known. Some people have a thin or absent area of bone on imaging without any symptoms. When the bony gap causes symptoms, doctors often use the term superior semicircular canal dehiscence syndrome. It most often comes to attention in middle-aged adults, but it can be found in younger adults and occasionally in children. It may affect one ear or both.

Superior semicircular canal dehiscence symptoms

Superior semicircular canal dehiscence symptoms vary widely from person to person. Some people have mainly hearing-related complaints, others have mainly balance-related complaints, and many have a mixture. Symptoms can be mild and easy to dismiss, or they can significantly interfere with daily life.

Common symptoms include:

• Autophony – hearing your own voice, breathing, chewing, footsteps or heartbeat unusually loudly inside the affected ear.
• Hearing your own eye movements or the sound of your eyes moving in their sockets.
• Dizziness or a spinning sensation (vertigo) triggered by loud sounds, a feature doctors call the Tullio phenomenon.
• Dizziness triggered by pressure changes, such as coughing, sneezing, straining, lifting heavy objects or pressing on the ear.
• A sense that the visual world bounces or moves when it should be still (oscillopsia), especially with loud noise or pressure.
• Persistent unsteadiness or imbalance, sometimes worse in crowded or busy visual environments.
• Pulsatile tinnitus – a rhythmic whooshing or pulsing sound in the ear in time with the heartbeat.
• A feeling of fullness or pressure in the ear.
• Hearing loss, typically for low-pitched sounds, that may be mistaken for a middle-ear problem.
• Difficulty tolerating noisy places, and in some cases a sense of "brain fog" or fatigue linked to constant balance effort.

Some people notice that their symptoms appear or worsen after a specific event, such as a head injury, a heavy lifting episode, a hard sneeze or an airplane flight. Others cannot identify any trigger, and symptoms build gradually. Symptoms do not usually follow fixed stages, but they can fluctuate. Because many of these complaints overlap with other inner-ear disorders, people are sometimes evaluated for several other conditions before superior semicircular canal dehiscence is considered.

Causes and risk factors

The exact superior semicircular canal dehiscence causes are not fully understood. The most widely accepted explanation involves two steps. First, the bone over the superior canal may develop abnormally thin before birth or fail to thicken normally during early childhood. Second, something later in life may cause this thin bone to wear away or break open, or may make an existing gap start to cause symptoms.

Factors that doctors believe may contribute include:

• Developmental thinning of the bone – many experts think the underlying weakness is present from birth, even if symptoms appear decades later.
• Head trauma – a blow to the head may crack or open an area of already thin bone.
• Sudden pressure changes – forceful coughing, straining, heavy lifting, scuba diving or air travel are sometimes reported just before symptoms begin.
• Raised pressure inside the skull – long-standing elevated intracranial pressure may gradually erode the thin bone from above. This is one reason the condition is seen more often in people with certain body types and in those with other signs of raised pressure.
• Age-related changes – the bone may thin further over time, which may help explain why symptoms often start in mid-life.
• Prior ear surgery or other skull base conditions – less commonly, disease or surgery near the canal can expose it.

Because a bony gap may be present without symptoms, having a dehiscence on a scan does not by itself mean a person has the syndrome. Doctors look for a match between the imaging finding, the symptoms and the results of specialized tests before making a diagnosis. Superior semicircular canal dehiscence is not thought to be infectious, and it is not caused by anything a person did wrong. It does not appear to be strongly hereditary, although research into genetic factors continues.

Diagnosis

Superior semicircular canal dehiscence diagnosis relies on combining a careful history with hearing tests, balance tests and imaging. No single test is enough on its own, because a thin area of bone on a scan can occur in people without symptoms, and because the hearing findings can look similar to other ear conditions.

A specialist, usually an ear, nose and throat doctor (otolaryngologist) with expertise in ear and balance disorders, will typically begin by asking detailed questions about your symptoms and any events that seemed to trigger them. During the examination, the doctor may play loud tones or apply gentle pressure to the ear canal while watching your eyes for characteristic movements, sometimes using special goggles that prevent you from fixing your gaze.

Tests that are commonly used include:

• Audiogram (hearing test) – people with this condition often show an apparent hearing loss for low-pitched sounds when tested through the air, but normal or even better-than-normal hearing when sound is delivered through the bone behind the ear. Some people can hear a tuning fork placed on an ankle or elbow, which is unusual.
• Tympanometry and acoustic reflexes – these measure how the eardrum and middle-ear muscles respond to sound and pressure. Normal results help separate superior semicircular canal dehiscence from middle-ear stiffening conditions that can cause a similar hearing pattern.
• Vestibular evoked myogenic potentials (VEMPs) – these tests record small muscle responses in the neck or below the eyes when a sound is played. In this condition the balance system tends to respond to quieter sounds than normal, and the responses tend to be larger than normal.
• High-resolution computed tomography (CT) of the temporal bone – a detailed X-ray scan of the ear bones is the key imaging test. The images are reformatted in the exact plane of the superior canal so the bony covering can be inspected. CT can suggest a gap where bone is merely very thin, so the result is interpreted together with the other tests.
• Video head impulse testing or other balance tests – these may be used to assess the overall function of the balance organs.
• Electrocochleography – a specialized recording of electrical activity from the inner ear that is abnormal in many people with a third window; it is used in some centers as supporting evidence.

Doctors generally diagnose the syndrome when the CT shows a dehiscence, the physiological tests show evidence of a third window, and the person has consistent symptoms. Other conditions that can mimic the symptoms, such as Meniere disease, otosclerosis, migraine-related dizziness or a patulous (abnormally open) Eustachian tube, are usually considered and excluded along the way.

Superior semicircular canal dehiscence treatment

Superior semicircular canal dehiscence treatment depends on how much the symptoms interfere with your life. Because the underlying problem is a physical gap in bone, medication cannot close it. Treatment choices therefore fall into two broad groups: managing symptoms without surgery, or surgically closing the third window.

Observation and lifestyle adjustments

Many people with mild symptoms do well without surgery. Your doctor may recommend:

• Avoiding known triggers such as very loud environments, heavy straining and activities that cause rapid pressure changes.
• Using earplugs or hearing protection in noisy settings.
• Treating conditions that increase pressure inside the head or chest, such as chronic cough, constipation or sleep apnea.
• Regular follow-up to check whether symptoms are stable, improving or worsening.

A ventilation tube placed in the eardrum is sometimes tried to reduce pressure-induced dizziness, but results are inconsistent and it does not help sound-induced symptoms or autophony.

Medication

There is no medicine that treats the dehiscence itself. Medications may occasionally be used for short periods to ease severe episodes of dizziness or nausea, or to manage coexisting conditions such as migraine or anxiety that can amplify balance symptoms. Long-term use of sedating anti-dizziness drugs is generally discouraged because it can slow the brain’s natural ability to compensate for balance problems.

Surgery

Surgery is usually reserved for people whose symptoms are disabling and whose diagnosis has been confirmed with imaging and physiological testing. The goal is to close the third window so that sound and pressure no longer stimulate the balance canal. Two main approaches are used:

• Middle fossa approach – a small opening is made in the skull above the ear, and the surgeon lifts the covering of the brain slightly to reach the top of the canal. The gap is then plugged with soft tissue and bone material, resurfaced with a graft, or both. This approach gives a direct view of the dehiscence.
• Transmastoid approach – the surgeon reaches the canal through the bone behind the ear, without opening the skull above the brain. The canal is opened on either side of the gap and plugged. This avoids lifting the brain but relies more heavily on imaging to locate the defect.

Plugging the canal intentionally stops that one canal from working. The other balance canals and the opposite ear usually compensate over time. Possible risks of surgery include hearing loss in the operated ear, temporary or occasionally lasting imbalance, leakage of the fluid that surrounds the brain, infection, and, rarely, more serious complications. Many people report substantial improvement in autophony and sound- or pressure-induced dizziness after successful surgery, but individual results vary, and your surgeon will discuss what is realistic in your situation.

Reinforcing the round window of the inner ear through the ear canal is a less invasive procedure that some surgeons offer. Its long-term effectiveness is debated, and it is not considered a standard replacement for canal plugging.

Vestibular rehabilitation

Balance retraining exercises guided by a physical therapist may help people who have ongoing unsteadiness, particularly in the weeks after surgery while the brain adjusts to the change in balance input. Rehabilitation does not close the dehiscence but can improve confidence and function.

At Acibadem, evaluation and management of this condition are handled within the Otorhinolaryngology (ENT) department, often together with audiology and, when surgery involves the skull base, neurosurgery.

Living with superior semicircular canal dehiscence and outlook

Superior semicircular canal dehiscence is not life-threatening, and for many people the symptoms remain stable over long periods. Some people learn to manage their triggers and find that the condition has a limited effect on daily life. Others find that constant autophony, noise sensitivity or unsteadiness affect work, sleep and social activities, and for them surgery may become a reasonable option after careful discussion.

Practical strategies that people often find helpful include keeping a symptom diary to identify triggers, using hearing protection in loud settings, pacing physical activities that involve straining, and explaining the condition to family, friends and employers so they understand why certain sounds or environments are difficult. Because balance problems can raise the risk of falls, keeping walkways clear and using good lighting at home are sensible precautions.

After surgery, recovery typically involves several weeks of gradually improving balance. Some people notice mild, lasting changes such as slight hearing differences or brief unsteadiness with quick head turns. In a minority of cases, symptoms persist or return, sometimes because the plug does not fully seal the canal or because the opposite ear also has a dehiscence. Regular follow-up allows your care team to monitor hearing and balance and to address any new concerns.

It is also common for people who have lived with unexplained symptoms for a long time to experience frustration, anxiety or low mood. Sharing these feelings with your doctor is worthwhile, because emotional stress can heighten the perception of dizziness and tinnitus, and support is available.

Frequently asked questions

What does superior semicircular canal dehiscence feel like?

People often describe hearing their own voice, chewing or eye movements loudly inside one ear, along with brief dizziness or a bouncing visual sensation triggered by loud sounds, coughing or straining. Others mainly notice a pulsing sound in the ear, a feeling of fullness, or general unsteadiness. Experiences vary, and not everyone has every symptom.

What causes superior semicircular canal dehiscence?

The condition is thought to begin with bone over the superior balance canal that is unusually thin from early life. Later, head injury, sudden pressure changes or long-standing raised pressure inside the skull may open the thin bone or make an existing gap start to cause symptoms. In many people no clear trigger is ever identified.

How is superior semicircular canal dehiscence diagnosed?

Doctors combine a detailed history, a hearing test, tests of the balance reflexes such as vestibular evoked myogenic potentials, and a high-resolution CT scan of the ear bones reformatted along the plane of the canal. A diagnosis is usually made only when the scan finding, the test results and the symptoms all point in the same direction.

Can superior semicircular canal dehiscence go away on its own?

The bony gap itself does not close on its own in adults. However, symptoms can fluctuate, and some people find that they lessen or become manageable over time, especially if triggers are avoided. Others experience gradual worsening. Your doctor may suggest a period of observation before considering any procedure.

What is the best treatment for superior semicircular canal dehiscence?

There is no single best option. Mild symptoms are often managed with trigger avoidance and monitoring. For disabling symptoms that have been confirmed by testing, surgery to plug or resurface the canal is the established treatment, and many people report meaningful relief, although results and risks vary from person to person.

Is surgery for superior semicircular canal dehiscence risky?

All ear and skull base surgery carries risks, including hearing loss in the operated ear, temporary imbalance, leakage of the fluid around the brain and infection. Serious complications are uncommon in experienced hands but cannot be ruled out. Your surgeon will explain the specific risks of the approach recommended for you.

Can superior semicircular canal dehiscence affect both ears?

Yes. Because the underlying bone thinning may be developmental, a proportion of people have a dehiscence on both sides, although symptoms are often worse in one ear. This is one reason doctors image both ears and usually treat only the more troublesome side first.

When to see a doctor

If you notice ongoing dizziness triggered by sounds or pressure, hear your own body sounds unusually loudly, or have a persistent pulsing noise or fullness in one ear, it is reasonable to ask for an evaluation by an ear specialist. Early assessment can help identify the cause and rule out other inner-ear conditions.

Seek urgent medical care if you experience any of the following, as they may indicate a different and more serious problem:

• Sudden loss of hearing in one or both ears.
• Severe vertigo accompanied by a new severe headache, double vision, slurred speech, facial drooping, weakness or numbness in the arms or legs, or difficulty walking.
• Clear, watery fluid draining from the ear or nose, particularly after a head injury or ear surgery.
• Fever, stiff neck and severe headache after ear or skull base surgery.
• A head injury followed by new dizziness, vomiting, confusion or drowsiness.
• A fall or loss of consciousness caused by dizziness.

These warning signs do not necessarily mean superior semicircular canal dehiscence is present, but they require prompt evaluation to exclude conditions such as stroke, infection or a leak of the fluid that surrounds the brain.