Superior semicircular canal dehiscence results from an opening (dehiscence) in the bone overlying the superior (uppermost) semicircular canal within the inner ear.
Who is affected by superior semicircular canal dehiscence syndrome?
The incidence of superior semicircular canal dehiscence syndrome is unknown. It is thought to affect men and women equally. Superior semicircular canal dehiscence probably arises from failure of postnatal bone development.
What are the symptoms of superior semicircular canal dehiscence syndrome?
Both vestibular and/or auditory symptoms can occur in superior semicircular canal dehiscence syndrome. Sound induced symptoms are typically described as the appearance of motion of objects in response to loud noises. Patients can experience dizziness and vertigo often triggered by heavy lifting, straining, coughing or loud sounds that change the middle ear or intracranial pressure. However some patients do not experience any dizziness. Other symptoms include fullness in the ear, autophony (which is an echo or reverberation in the ear when speaking, chewing or swallowing or hearing loss. Similarly others patients can experience Oscillopsia (the apparent motion of objections that are known to be stationary) which are caused by the manoeuvres previously mentioned; others may perceive that objects are moving in time with their pulse (pulsatile oscillopsia).
What investigations are necessary to make the diagnosis?
There are many conditions that resemble superior semicircular canal dehiscence syndrome including BPPV, Ménière’s disease, labyrinthitis and otosclerosis. Therefore it is necessary to rule out the other vestibular conditions. Caloric testing may be important to exclude unilateral vestibular hypofunction cause by Ménière’s or labyrinthitis. The diagnosis of superior semicircular canal dehiscence syndrome is made based upon characteristic symptoms, specific findings of a patient’s medical history, on clinical examination, CT imaging, and findings on vestibular evoked myogenic potentials (VEMP) testing.
How is superior semicircular canal dehiscence syndrome disease treated?
Patients often avoid loud noises which may be sufficient treatment, however for those who are debilitated by their symptoms surgical plugging of the superior canal can be very beneficial in alleviating the symptoms.