Canal Dehiscence Syndromes

Superior canal dehiscence syndrome (SCDS) is a rare medical condition of the inner ear, leading to hearing and balance disorders in those affected. The symptoms are caused by an absence of the part of the temporal bone overlying the superior semicircular canal of the vestibular system. This may result from slow erosion of the bone or physical trauma to the skull and there is evidence that the defect or susceptibility is congenital. SCDS can affect both hearing and balance, to different extents in different people and symptoms may include autophony (person's own speech or other self-generated noises, e.g. heartbeat, eye movements, are heard unusually loudly in the affected ear); dizziness, vertigo or chronic disequilibrium; Tullio phenomenon (sound-induced vertigo or disequilibrium or dizziness, nystagmus and oscillopsia); pulse-synchronous oscillopsia; hyperacusis (over-sensitivity to sound); low-frequency conductive hearing loss; feeling of fullness in the affected ear; pulsatile tinnitus; fatigue; headache.

According to current research, in approximately 2.5% of the general population, the bones of the head develop to only 60-70% of their normal thickness in the months following birth. This genetic predisposition may explain why the section of temporal bone separating the superior semicircular canal from the cranial cavity, normally 0.8 mm thick, shows a thickness of only 0.5 mm, making it more fragile and susceptible to damage through physical head trauma or from slow erosion.

The presence of dehiscence can be detected by a high definition coronal CT scan of the temporal bone. Other diagnostic tools include vestibular evoked myogenic potential (VEMP test), videonystagmography (VNG), electrocochleography (ECOG) and the rotational chair test.

Once diagnosed, the gap in the temporal bone can be repaired by surgical resurfacing of the affected bone or plugging of the superior semicircular canal. These techniques are performed by accessing the site of the dehiscence either via a middle fossa craniotomy or a transmastoid approach.

At House Clinic, we offer all surgical approaches and tailor the treatment to the patient.