Superior Canal Dehiscence

Superior canal dehiscence is a rare condition affecting the uppermost portion of the inner ear canal. It occurs when the bones of the inner ear become thin, damaged, or develop a hole, which creates additional pathways for fluid inside the inner ear. Superior canal dehiscence is believed to affect approximately 1 to 2 percent of the population and is most common in adults in their 40s.

• It is believed that the condition affects men and women in equal numbers
• Superior canal dehiscence is believed to be associated with increased fluid pressure in the brain and skull

The inner ear contains three semicircular canals. These structures contain fluid and tiny hairs that move when the body moves. This lets the brain know how the body is positioned so that it can tell the rest of the body how to react to maintain balance. When the bone of the uppermost semicircular canal develops a hole or becomes too thin, it can affect how the brain and body perceive movement and cause hearing issues and sensitivity to sound. Although superior canal dehiscence can occur with no apparent cause, some factors that may contribute to the condition include:

Superior canal dehiscence is a rare condition affecting the uppermost portion of the inner ear canal. It occurs when the bones of the inner ear become thin, damaged, or develop a hole, which creates additional pathways for fluid inside the inner ear. Superior canal dehiscence is believed to affect approximately 1 to 2 percent of the population and is most common in adults in their 40s.

• Infectious diseases
• Trauma to the bones of the inner ear
• Genetic conditions that prevent the bones of the inner ear from developing normally

Although it is possible to have superior canal dehiscence without any symptoms, it is common for the condition to cause dizziness and a sense of being off balance.

• Increased fluid in the inner ear can cause a feeling of fullness or pressure that does not improve by popping the ears
• Increased fluid in the inner ear can cause a feeling of fullness or pressure that does not improve by popping the ears
• There may be hearing loss on the affected side
• Patients often hear internal sounds, such as their own heartbeat, louder than normal and may notice a ringing in their ears
• Patients often hear internal sounds, such as their own heartbeat, louder than normal and may notice a ringing in their ears
• Objects may appear to be moving when they are actually still

The severity of symptoms can vary based on the exact location of the defect and the amount of the inner ear membrane that is exposed. Sneezing, coughing, straining, lifting heavy objects, altitude changes, and exposure to loud sounds may trigger the symptoms.

A videonystagmography, also known as a VNG test, may be used to detect and measure eye movements that may indicate a balance problem. This involves applying small electrodes around the eyes. The patient is then guided through certain eye and head movements as the results are monitored and recorded on video.

A vestibular evoked myogenic potentials test, also known as a VEMP test, may be used to measure the reflex in the neck muscle that reacts to sound. The test is performed by placing an electrode on the neck along the appropriate muscle. The patient is then asked to listen to low to mid-range sounds in one ear as the doctor views the results on a monitor.

A computed tomography scan of the ear may be performed to determine if there are any holes or thinning bones in the superior canal.

If the symptoms are minor, simply avoiding triggers may be enough to manage the condition. Hearing aids may help compensate for mild hearing loss. Surgery, however, may be necessary in more severe cases involving balance problems or echoing of sounds in the ears.

The decision to undergo surgery to correct superior canal dehiscence is largely determined by the severity of the symptoms, the individual’s activity level, and their ability to avoid triggers that may exacerbate their symptoms.

The most common surgical technique for correcting superior canal dehiscence is the middle fossa approach. This involves making a small opening in the skull above the affected ear to allow the surgeon access to the canal. Fibrous tissue secured by small bone chips is then used to plug the affected canal.

An alternative technique is known as the transmastoid approach. With this method, the canal is accessed through a skull opening made behind the ear. The affected canal is then plugged to prevent the flow of fluid.

A new technique known as round window plugging accesses the inner ear directly through the ear canal. Similar to the other techniques, the affected canal is then plugged to limit the flow of fluid.