What is Superior Semicircular Canal Dehiscence?

Superior Semicircular Canal Dehiscence (SSCD) is a rare inner ear condition affecting hearing and balance. It is caused by thinning or absence of part of the temporal bone, which protects the cochlea (hearing component) and fluid-filled canals (balance component) of the inner ear.

These normally work independently, however, patients with some conditions or diseases have reported that sounds can cause vertigo (spinning sensations) and nystagmus (eye movements).

In patients with SSCD, sound causes the fluid in the balance canals to move, which gives the person the impression that they are physically moving. This can be a minor and temporary inconvenience or a major disability. In many cases, the imbalance disappears when the condition is addressed.

Superior Semicircular Canal Dehiscence
Superior Semicircular Canal Dehiscence

What are the Symptoms?

Patients show one or more of these symptoms:

  • Imbalance;
  • Hearing loss;
  • High sensitivity or intolerance to sounds of a certain frequency or type (e.g. a mobile phone ringing or a child crying);
  • Motion intolerance; or
  • Hearing internal sounds like eye movements or walking.

Some patients experience their eyes moving suddenly to compensate for an inner motion. Sound normally moves the fluid in the cochlea which activates the hair cells and turns the sound into electrical signals. This same fluid is shared by the balance canals. Loud sounds change the pressure of the fluid in the cochlea and the canals. This may result in slight movement of the thinned bone, which is interpreted by the brain as physical movement. If the patient’s eyes are open, visual cues tell the brain that there is no movement. This confusion results in feelings of imbalance and, often, the eye movement.

What Causes the Condition?

The cause of the condition is not fully understood. Some people are born with thinner bone over the superior semicircular canal, which can lead to the condition naturally or after trauma.

Diagnosis

Diagnosis includes a hearing test, tests in a vestibular clinic to assess eye movement, and usually a CT scan. Identifying the direction of the eye movements helps to determine if the problem is on the left or right side, while a CT scan can find the thinning bone.

Treatment

Patients seen by specialists at Ear Science Surgery have been successfully treated in one of two ways:

  • Diagnosis and counselling
    A number of patients have been assisted merely by the diagnosis, which allows them to avoid the condition/s that trigger an attack. After many years of living with the condition they are relieved to have an explanation.
  • Surgery
    Professor Marcus Atlas and the team at Ear Science Surgery are experts in the surgical treatment of SSCD, and surgery to repair the thinning bone is often successful. This surgery must be performed under a general anaesthetic, and requires drilling through a section of the skull above the ear to block the ear superior canal and then use a cement to thicken the covering. This completely resolves the issue for most patients, and significantly reduces it for others.

Reference

74.Gluth MB, Eager KM, Eikelboom RH, Atlas MD, Long-term benefit perception, complications, and device malfunction rate of bone-anchored hearing aid implantation for profound unilateral sensorineural hearing loss. Otol Neurotol. 2010 Dec;31(9):1427-34

33.Atlas MD, Lowinger DSG. The GP’s essential guide to hearing loss. Medicine Today. 2000;48-59.

32. Atlas MD, Lowinger DSG.Office of evaluation of hearing loss in adults. Medicine Today. 2000;117-119.