What is superior canal dehiscence (SCD)?
Canal dehiscence refers to an opening (dehiscence) in the bone that covers one of the semicircular canals of the inner ear. It most commonly occurs in the superior semicircular canal of the ear. It can result in symptoms that affect a person's balance and hearing.
What causes superior canal dehiscence (SCD)?
The true cause of canal dehiscence syndrome is unknown. The dehiscence may, at least in part, be congenital (present from birth) and may have occurred during the development of the inner ear. It can also be caused from certain infections as well as head trauma. Many believe that it is multifactorial in that there may be a congenitally thin area of bone that is then susceptible to trauma or infections, or may simply thin further with aging.
It is estimated that approximately 1 to 2% of the general population has abnormally thin bone covering their superior semicircular canal. The average age for diagnosis of superior canal dehiscence is approximately 45 years old. Approximately 33% of patients diagnosed will have superior canal dehiscence in each ear. Many people will have thin or dehiscent bone on scans, but no symptoms at all of SCD syndrome. Interestingly, some individuals with only thin bones on scans may present with the same symptoms as some with true dehiscence.
What are the symptoms of superior canal dehiscence (SCD)?
Symptoms of superior canal dehiscence can include:
- Vertigo (dizziness)
- Oscillopsia (appearance of movement of stationary objects)
- Autophony (hearing one's voice or self-generated sounds like breathing and blinking louder than normal)
- Sensitivity to loud sounds
- Fullness/pressure in the ears
Although it may not be directly related, it is not uncommon to also have a headache with this condition.
The vertigo and oscillopsia commonly associated with canal dehiscence can be triggered by common activities that change the pressure in the brain or the middle ear, and by exposure to loud sounds. These activities include straining, coughing, sneezing, heavy lifting, exercising, and listening to loud noises.
Not all patients will expereince all of the symptoms, which can make the diagnosis difficult and can alter the treatment recommendations.