Superior Semicircular Canal Dehiscence Syndrome
Definition of SCDS
Lloyd Minor, M.D., was the first to describe this syndrome in 1998. It usually affects men more commonly than women in their 30s to 40s. Patients often complain of dizziness and vertigo usually triggered by straining, heavy lifting, or loud, usually low frequency sounds. Other common complaints include fullness in the ear(s), autophony (an echo or reverberation of the ear when speaking, chewing, or swallowing), or hearing loss. Some complain that they can hear their own heartbeat in the affected ear.
Patients with SCDS can have dizziness and/or hearing loss. In most cases, a blocked or fullness sensation of the ear is fairly consistent across most patients with SCDS. Some SCDS patients only have fullness or hearing loss. Dizziness is NOT seen in all patients with SSCD.
What is the problem in SCDS?
The superior semicircular canal is one of three paired canals which in part, comprise the balance organs of the inner ear. The superior (also called the anterior), posterior, and horizontal semicircular canals sense head movements, stabilizing eye movements in response to angular acceleration.
The defect is a small hole in the inner ear bone, measuring less than 1mm to up to 5mm in size, of the superior semicircular canal. SCDS appears to be more common on the left side, but can be seen on the right side, or on both sides. Often, the skull base surrounding the SCD is also very thin or perforated.
In autopsy specimens, examination of temporal bones, the region of the skull base which houses the inner ear - the cochlear and the vestibular organs, including the semicircular canals - reveal that 2% have abnormal thinning or breakdown (dehiscence) of the superior semicircular canals. It is felt to be a developmental abnormality. It is rare for SCDS to present early in life - most patients are diagnosed in their 30s to 40s. However, only recently have otolaryngologists become aware of this condition and, with improvements in diagnostic methods (especially audiologic and radiologic) we would expect that more patients will be diagnosed with this condition at earlier ages.
In a meta-analysis by Watters et al 53% of patients with SCDS who needed surgery had the condition on the left, 23% on the right, and 23% were bilateral (both sides)
What conditions resemble SSCD?
Many patients with SCDS have often been treated for a number of otologic conditions before the correct diagnosis is made by a specialist.
SCDS can resemble these more common conditions:
- Eustachian Tube Dysfunction
- Patulous Eustachian Tube
- BPPV (Benign Paroxysmal Positional Vertigo)
- Meniere's Disease
- Vestibular Neuronitis / Neuritis