SCDS is a rare but quite distinct (and fascinating) condition. It is characterized by abnormal thinning or loss of a small area of skull bone that covers the superior semicircular canal of the inner, resulting in abnormal transmission of sound and pressure to this canal.
Symptoms of SCDS include:
- Pulsatile tinnitus
- due to hearing the sound of one’s own heart beat in the affected ear
- Vertigo and nystagmus triggered by certain sounds
- Vertigo and nystagmus triggered by straining (e.g. coughing, blowing one’s nose)
- Increased sensitivity to self-generated noises. Different descriptions of this phenomenon include:
- finding their breathing is too loud
- hearing their eyes move
- hearing their footsteps
- hearing their joints creak
- finding their own voices are too loud and are distorted
- Increased sensitivity to noises
- Low frequency conductive hearing loss
Tests like audiograms, vestibular evoked myogenic potentials (VEMPs), electrocochleography, and video-nystagmography (VNG) can provide vital clues about SCDS.
A temporal bone CT scan (not an MRI or a general head CT) is the best test to identify the thinning or loss of the temporal bone overlying the superior semicircular canal.
If the symptoms affect a patient’s life significantly, surgical repair of the dehiscence can be performed. Surgical approaches include transmastoid (i.e. through the mastoid bone) or middle fossa craniotomy. The best approach should be discussed with a neuro-otologist.