Superior Canal Dehiscence Syndrome

Superior Canal Dehiscence Syndrome
Richard Irving MD FRCS (ORL-HNS)

Patients with this condition typically present with sound and/or pressure induced vertigo. They also may describe symptoms of hyperacusis to bone conducted sound
in their affected ear such as autophony, and in some cases the ability to hear their own eye movements. The clinical examination may be normal but it is important to
look for sound or pressure induced nystagmus that is typically short lived and with both a vertical and a torsional component. It is important to measure bone conduction thresholds even if air conduction values are normal since these patients frequently have supra-normal bone conduction in the affected ear. Some present as an unexplained conductive loss and can be misdiagnosed as otosclerosis. The diagnosis is made in a patient with of a typical history and characteristic features on
CT and vestibular evoked myogenic potential testing (VEMP). Image interpretation can be difficult and it is recommended that CT scans are reconstructed and viewed
in the plane of the superior canal. Since 2003 patients suspected to have this condition from around the UK have been evaluated at the Multidisciplinary Balance Clinic at the Queen Elizabeth Hospital in Birmingham. Many patients with superior canal dehiscence are mildly affected and respond to reassurance and advice on avoidance of noxious stimuli. The author has been offering surgery to those unable to tolerate their symptoms and patients treated surgically over the last 13 years will be presented. The surgical technique has evolved from a middle fossa craniotomy to the authors’ current preference for a trans-mastoid approach. Surgery carries a risk of imbalance and hearing loss but the vast majority derive significant relief of their symptoms by plugging the affected canal.