Superior Canal Dehiscence

Superior Canal Dehiscence is a condition characterized by a combination of multiple symptoms. Most common symptoms are listed below:

• Sensation of hearing their own voice in their ear (autophony)

• Feeling of a plugged ear which doesn't resolve with popping the ear

• Dizziness that occurs with loud noise or with pressure. The dizziness is usually very short lasting (a few seconds) and there is a sensation that the visual field rotates a bit with coughing, sneezing, lifting something heavy, or with loud noise.

• Hearing loss - most commonly conductive but can be mixed. A characteristic of the hearing test is that the inner ear hearing (bony thresholds) are better than normal, but when the hearing is tested through the ear canal, there is a hearing loss.

• A feeling that one can hear internal sounds. For example, patients often have a sensation of hearing their heartbeat or sometimes even hearing their eyes move.

 

What Causes It?

The bony portion of one the canals of the inner ear (superior canal - the top-most canal) gets eroded away probably because of pressure and pulsations of the brain. Sometimes this can occur after a trauma that causes a sudden pressure change in the brain which can break the thinned bone. This causes the inner ear fluid compartments to have an outflow tract which leads to the symptoms of dizziness, hearing loss, and especially the sensitivity to sound (which causes vertigo).

How Do We Diagnose It?

The best way to diagnose it after clinical suspicion is to perform a CT scan of the temporal bone and confirm the diagnosis with a VEMP test. This scan has to be obtained in a very special way. It has to be done using slice thickness that is under 1 mm. If the scan is done with 1 mm thickness or larger, then it may show a dehiscence when it may not be present.

The VEMP test (vestibular evoked myogenic potential) is a test of a particular part of the balance organ. This test involves sending sound to the ear while the neck muscle is under tension. A lower threshold and higher amplitude on the VEMP test in the presence of a CT finding is highly suggestive of a superior canal dehiscence.

Treatment Options

There are 2 options for dealing with this problem. 1. do nothing and avoid the problems that cause the symptoms. For example, some of our patients have somewhat sedentary lifestyles and do not engage in activities that cause dizziness and they can put up with the minor symptoms.

The Second option is to have surgery for repair of a superior canal dehiscence. There are currently a few approaches to this treatment.

1. Middle fossa Approach. The treatment of superior canal dehiscence is by doing surgery and patching the hole in the superior canal from above the ear. This is called a middle fossa approach and it usually requires a craniotomy (opening the skull). This requires a 2-4 day hospital stay usually.

2. Transmastoid approach. In this approach, the surgery is done from going behind the ear. This procedure is done in an outpatient fashion (patient goes home the same day).

3. Round window plugging approach. This approach is done by going through the ear canal and plugging one of the areas of the inner ear (not the superior canal). This procedure has only been reported by one group in a few patients and has not obtained wide acceptance.

Why come to UC Irvine?

At UC Irvine, we strive to be innovative and the best comprehensive center in the treatment of dizziness. Before many centers started the transmastoid approach, which is less invasive but more technically challenging, Dr. Djalilian performed this procedure at UC Irvine.