Superior semicircular canal dehiscence: a narrative review.

ABSTRACT

BACKGROUND: Described just over 20 years ago, superior semicircular canal dehiscence remains a relatively unknown and easily missed cause of dizziness and auditory symptoms. OBJECTIVE: This review focused on the origin, presenting symptoms and underlying pathophysiology of superior semicircular canal dehiscence, and the available treatment options. MAIN FINDINGS AND CONCLUSION: The bony dehiscence acts as a 'third window', affecting inner-ear homeostasis, and resulting in hypersensitivity and a vestibular response to lower sound level stimuli. The third window effect explains the pressure- and sound-induced vertigo, oscillopsia, and nystagmus, as well as autophony, conductive hyperacusis and tinnitus. The origin of superior semicircular canal dehiscence is linked to the combination of a congenital or developmental factor, and a 'second event' like head trauma, rapid pressure changes or age-related factors. Computed tomography of the temporal bone and reduced vestibular-evoked myogenic potential thresholds can confirm the diagnosis. Despite only retrospective cohorts, surgery is considered a safe treatment option, targeting mainly vestibular but also auditory symptoms, with transmastoid approaches gaining popularity.