Superior Canal Dehiscence
Superior canal dehiscence is when there is an opening in the bone that lays over an area of the inner ear called the superior semicircular canal.
There are multiple symptoms with this condition, including:
Sensation of hearing your own voice in your ear, called autophony.
- A "plugged ear" feeling that doesn't go away 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 is 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 hearing loss.
- A feeling that you can hear internal sounds. Patients often have a sensation of hearing their heartbeat or sometimes even hearing their eyes move.
The bone erosion that happens with superior canal dehiscence is caused likely caused by pressure and pulsations of the brain.
This can occur after a trauma that causes sudden pressure changes in the brain, which can break bones that have thinned.
The break causes inner ear fluid compartments to leak, leading to dizziness, hearing loss and sensitivity to sound (which leads to vertigo).
The best way to diagnose superior canal dehiscence suspicion is to perform a CT scan of the temporal bone, then confirm the diagnosis with a vestibular evoked myogenic potential (VEMP test).
It is important to have a skilled technician perform the CT scan. If the scan is done improperly, it can show a dehiscence when there isn't one.
The VEMP test is a test of a particular part of the balance organ. It 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.
There are two options for dealing with this condition:
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- 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. This enables them to cope with the minor symptoms.
- Middle fossa surgery. 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 two to four day hospital stay usually.
- Transmastoid surgery. 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). Our surgeons are highly experienced in this technically challenging approach.
- Round window plugging surgery. 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.