Superior Canal Dehiscence Syndrome (SCDS) is caused by an abnormal thinness or incomplete closure of one of the bony canals in the inner ear. This physical defect is the root cause of the various symptoms associated with SCDS.
Understanding SCDS and Its Cause
SCDS arises when the bone overlying the superior semicircular canal in the inner ear is thinner than normal or entirely absent. This creates an opening, or "dehiscence," where normally solid bone should be. This dehiscence alters the normal pressure dynamics within the inner ear.
How the Dehiscence Affects the Inner Ear
- Normal Function: The inner ear contains fluid-filled semicircular canals that help with balance and hearing. These canals are encased in bone, which helps maintain appropriate pressure.
- SCDS Effect: The dehiscence, or opening, in the bone disrupts this pressure control. It creates an abnormal third mobile window (besides the oval and round windows) that allows sound and pressure changes to affect the inner ear in unusual ways.
Symptoms Triggered by the Dehiscence
This bony defect can result in a range of symptoms, particularly those triggered by loud noises or increases in intracranial pressure. Symptoms include:
- Hearing Loss and Sound Distortion: The abnormal pressure changes in the inner ear can lead to hearing loss, autophony (hearing one's own voice or body sounds unusually loud), or distortion of sounds.
- Balance Problems: The semicircular canals also play a vital role in balance. The pressure changes can cause vertigo or a sense of imbalance. These issues can be particularly triggered by sudden changes in pressure such as from loud sounds, sneezing or coughing.
Examples of Symptom Triggers
- Loud noises: Can induce dizziness or hearing distortion.
- Sneezing or coughing: Increases intracranial pressure and causes symptoms.
- Valsalva maneuvers : Can lead to pressure changes that affect balance and hearing.
In Summary
In short, SCDS is caused by an abnormal thinness or incomplete closure of one of the bony canals in the inner ear. This abnormality allows pressure to move abnormally within the inner ear, triggering symptoms such as hearing loss, sound distortion, and balance problems that can be brought on by loud sounds or pressure changes. The dehiscence is the fundamental cause of the syndrome.
