Superior semicircular canal dehiscence: An unusual cause of vertigo

A 29-year-old man with complaints of rotatory vertigo, right side conductive hearing loss, tinnitus and autophony presented to the outpatients department of ENT. He had normal otoscopic examination. Cervical vestibular-evoked myogenic potential was abnormal (Fig. 1). High-resolution computed tomography temporal bone (plane of Pöschl) revealed a dehiscence of the right superior semicircular canal (Fig. 2). Superior semicircular canal dehiscence or Minor syndrome is a rare disorder characterized by the absence of bone overlying the superior semicircular canal resulting in a third window to membranous labyrinth that may result in a syndrome of vestibular and/or auditory symptoms.

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FIG 1.

Vestibular-evoked myogenic potentials are present when stimulated with 95, 90, 80 and 70 dB stimuli. Thresholds are reduced and amplitudes are increased on the right side suggestive of abnormal cervical vestibular-evoked myogenic potential findings

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FIG 2.

Pöschl view of the temporal bone showing dehiscence of the right superior semicircular canal. The plane of projection is perpendicular to the long axis of the temporal bone

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