Superior Canal Dehiscence Syndrome

Superior Canal Dehiscence Syndrome (SCDS) is a rare inner ear condition where a small hole or thinning occurs in the bone covering one of the balance canals. This defect creates an abnormal opening, often called a "third window," which can lead to a range of unusual hearing and balance symptoms.

What is Superior Canal Dehiscence Syndrome?

Superior Canal Dehiscence Syndrome (SCDS) is a rare disorder affecting the inner ear, specifically involving a defect in the bone that covers the superior semicircular canal. This canal is one of three fluid-filled loops that help your brain understand head movements and maintain balance. The bone defect creates an abnormal opening, often called a "third window," which disrupts the normal pressure dynamics within the inner ear.

Normally, the inner ear is a closed system. In SCDS, the thinning or absence of bone over the superior semicircular canal allows sound and pressure to abnormally move the fluid inside this canal. This movement can send incorrect signals to the brain, leading to a variety of symptoms. This condition can affect one ear or, less commonly, both ears. It is considered rare, though its exact prevalence is not precisely known. The symptoms experienced by individuals with SCDS can vary widely in type and severity, making diagnosis challenging at times. The superior semicircular canal is crucial for detecting rotational head movements. When a dehiscence (defect) is present, it can cause the inner ear to become overly sensitive to internal and external sounds and pressure changes, leading to the characteristic symptoms of the syndrome.

Symptoms

Symptoms of Superior Canal Dehiscence Syndrome (SCDS) typically involve unusual hearing sensations and balance problems, often triggered by loud sounds or changes in pressure. These can include hearing your own body sounds too loudly, dizziness, or a feeling of ear fullness. The specific symptoms and their intensity can differ greatly among individuals.

One of the most distinctive symptoms is autophony, which is hearing internal body sounds much louder than normal. This can include hearing your own voice, heartbeat, eye movements, or even the sound of your joints moving. Your own voice might sound unusually loud or distorted in the affected ear. Many people with SCDS experience sound-induced dizziness or vertigo, known as the Tullio phenomenon. This means certain loud noises can trigger feelings of spinning or unsteadiness. Similarly, pressure changes, such as those from coughing, sneezing, straining, or lifting heavy objects (Valsalva maneuver), can also cause dizziness or vertigo. Other common symptoms include pulsatile tinnitus (hearing a rhythmic whooshing or throbbing sound, often in sync with your heartbeat), a feeling of fullness or pressure in the ear, and sometimes conductive hearing loss. Some individuals also report hyperacusis (increased sensitivity to certain everyday sounds), brain fog, fatigue, and a general sense of imbalance or unsteadiness.

Causes & risk factors

The exact cause of Superior Canal Dehiscence Syndrome (SCDS) is often unknown, but it is believed to result from a combination of factors. The bone defect may be present from birth (congenital) or develop over time due to bone thinning. Certain events, like head trauma or rapid changes in intracranial pressure, might trigger symptoms in individuals who are already predisposed.

While the precise reason for the bone thinning or absence is not fully understood, it is thought that some people may have a genetic predisposition that makes them more susceptible. The bone covering the superior semicircular canal is naturally thinner in some individuals. In many cases, symptoms appear spontaneously without a clear trigger. However, some people report that their symptoms began after a specific event, such as a head injury, a sudden change in altitude or pressure, or even intense physical exertion. These events are thought to unmask an existing, underlying dehiscence rather than directly cause it. It is important to understand that SCDS is not caused by anything you did or did not do. It is a structural issue within the inner ear. Research continues to explore the genetic and environmental factors that might contribute to its development.

How it's diagnosed

Diagnosing Superior Canal Dehiscence Syndrome (SCDS) involves a combination of tests to confirm the presence of the bone defect and assess its impact on hearing and balance. A doctor will typically start with a physical exam and discuss your symptoms. Specialized hearing and balance tests, along with imaging scans, are crucial for an accurate diagnosis.

The diagnostic process usually begins with a thorough medical history and a physical examination. Your doctor will ask about your specific symptoms, when they started, and what triggers them. They will also perform a neurological exam and check your ear. Specialized hearing tests, such as an audiogram, can detect conductive hearing loss or other hearing abnormalities. Balance tests are also key; a vestibular evoked myogenic potential (VEMP) test is particularly useful as it can detect the abnormal sensitivity of the inner ear to sound or vibration that is characteristic of SCDS. Videonystagmography (VNG) may also be used to assess eye movements related to balance. The definitive diagnosis of SCDS is confirmed with a high-resolution computed tomography (CT) scan of the temporal bone. This specialized imaging technique can clearly show the thinning or absence of bone over the superior semicircular canal, providing visual evidence of the dehiscence. It is important that the CT scan is interpreted by a radiologist experienced in identifying this specific condition.

Treatment options

Treatment for Superior Canal Dehiscence Syndrome (SCDS) depends on the severity of your symptoms. For mild cases, observation and managing triggers may be sufficient. For more severe or debilitating symptoms, surgical intervention is often recommended to repair the bone defect and alleviate the abnormal inner ear pressure.

If your symptoms are mild and do not significantly interfere with your daily life, your doctor may recommend a conservative approach. This involves monitoring your symptoms over time and trying to avoid specific triggers, such as loud noises or activities that cause pressure changes. For individuals with severe or persistent symptoms that impact their quality of life, surgery is the primary treatment option. The most common surgical approaches involve either plugging the dehiscence or resurfacing the bone over the superior semicircular canal. These procedures aim to close the "third window" and restore normal inner ear mechanics. Two main surgical techniques are used: the middle fossa craniotomy approach, which involves accessing the inner ear through the skull above the ear, and the transmastoid approach, which goes through the mastoid bone behind the ear. A less common and generally less effective option is round window reinforcement. Your surgeon will discuss the best approach for your specific situation, considering the risks and benefits of each.

Recovery & outlook

The recovery and outlook for Superior Canal Dehiscence Syndrome (SCDS) after surgery are generally positive, with many people experiencing significant improvement or resolution of their symptoms. However, recovery can take time, and like any surgery, there are potential risks and complications. The long-term outlook is typically good for those who undergo successful surgical repair.

After surgery for SCDS, most individuals report a substantial reduction or complete resolution of their debilitating symptoms, such as autophony, sound-induced dizziness, and pressure sensitivity. The success rate for symptom improvement is high, though it can vary depending on the surgical approach and individual factors. Recovery from surgery can involve a period of discomfort, including pain, temporary dizziness, and fatigue. The full benefits of the surgery may not be apparent for several weeks or even months as the inner ear heals and the brain adapts to the restored balance system. Physical therapy may be recommended to help with any lingering balance issues. Potential risks of SCDS surgery, though uncommon, include hearing loss, cerebrospinal fluid (CSF) leak, infection, and persistent or new balance problems. It is important to discuss these risks thoroughly with your surgeon. For many, the improvement in quality of life after successful surgery makes the procedure a worthwhile option.

When to see a doctor

You should see a doctor if you experience persistent or worsening symptoms that suggest Superior Canal Dehiscence Syndrome (SCDS), especially if they affect your daily activities. These include unusual hearing of internal body sounds, dizziness triggered by sounds or pressure, or unexplained balance problems. Early evaluation can lead to an accurate diagnosis and appropriate management.

It is important to seek medical attention if you notice any of the characteristic symptoms of SCDS. This includes hearing your own heartbeat, eye movements, or voice much louder than usual, or if you experience dizziness or vertigo when exposed to loud sounds or changes in pressure. Also, if you have unexplained conductive hearing loss, a constant feeling of ear fullness, or chronic imbalance that is not improving, it's a good idea to consult a healthcare professional. These symptoms can sometimes be mistaken for other conditions, so an accurate diagnosis is crucial. Your primary care doctor can refer you to a specialist, such as an otolaryngologist (ear, nose, and throat doctor) or a neurotologist, who has expertise in inner ear disorders. They can perform the necessary tests to determine if SCDS is the cause of your symptoms and discuss potential treatment options.

Frequently asked questions

Can Superior Canal Dehiscence Syndrome (SCDS) cause brain fog?

Yes, many individuals with SCDS report experiencing symptoms of brain fog, which can include difficulty concentrating, memory problems, and a general feeling of mental fatigue. This is thought to be due to the constant overstimulation of the inner ear and the brain's effort to compensate for the abnormal signals, leading to cognitive strain.

Are there non-surgical treatments for SCDS?

For mild symptoms, non-surgical management focuses on avoiding triggers like loud noises or activities that cause pressure changes. However, there are no medications or therapies that can repair the bone defect itself. For significant symptoms, surgery is currently the only effective treatment to address the underlying structural problem.

Can SCDS symptoms fluctuate or get worse over time?

Yes, SCDS symptoms can fluctuate in intensity. They may be worse during periods of stress, fatigue, or after exposure to specific triggers. While some individuals experience stable symptoms, others find their symptoms gradually worsen over time, particularly if the bone defect progresses or if new triggers emerge.

Is SCDS hereditary?

While the exact cause is often unknown, there is some evidence to suggest a possible genetic predisposition to SCDS. Some individuals may be born with thinner bone in that area, making them more susceptible to developing a dehiscence. However, it is not considered a purely hereditary condition that is passed directly from parent to child.

Can SCDS be misdiagnosed?

Yes, SCDS can sometimes be misdiagnosed because its symptoms can overlap with other conditions, such as Meniere's disease, otosclerosis, or even anxiety disorders. The unique combination of hearing and balance symptoms, especially autophony and sound/pressure-induced dizziness, should prompt specific diagnostic tests like a high-resolution CT scan to confirm SCDS.

Can I fly or scuba dive with SCDS?

Flying can potentially worsen SCDS symptoms due to changes in cabin pressure, which can exacerbate pressure-induced dizziness. Scuba diving is generally not recommended for individuals with SCDS due to the significant pressure changes involved, which could be dangerous and severely worsen symptoms. It's crucial to discuss these activities with your doctor.

Sources

• MedlinePlus — Superior Canal Dehiscence Syndrome
• Mayo Clinic — Superior Canal Dehiscence Syndrome
• Cochrane Library — Superior Canal Dehiscence Syndrome