Superior canal dehiscence syndrome.

OBJECTIVE: To present the symptoms, signs, and findings on diagnostic tests of patients with the superior canal dehiscence syndrome and to describe the surgical procedures used to treat the dehiscence in five patients.

DESIGN AND SETTING: Prospective study of a series of patients identified as having this syndrome at a tertiary care referral center.

PATIENTS AND RESULTS: Seventeen patients with vertigo, oscillopsia, or both evoked by intense sounds or stimuli that caused changes in middle ear and/or intracranial pressure were identified over a 4-year period. The evoked eye movements had vertical and torsional components, with the direction corresponding to the effect of the stimuli in causing excitation (Valsalva against pinched nostrils, tragal compression, sounds) or inhibition (Valsalva against a closed glottis or jugular venous compression) of the affected superior semicircular canal. Thirteen (76%) of these patients also experienced chronic dysequilibrium that was often the most debilitating symptom. Dehiscence of bone overlying the superior semicircular canal on the affected side was confirmed with computed tomographic scans in each case. Surgical procedures through the middle fossa approach to plug or resurface the superior canal were performed in five patients (canal plugging in three cases and resurfacing of the dehiscence without plugging in two). The debilitating symptoms resolved or improved after the procedures. Signs of vestibular hypofunction, without loss of hearing, were noted in one patient after plugging of the superior canal and in one other patient after resurfacing of the canal.

CONCLUSIONS: The superior canal dehiscence syndrome is identified based on characteristic symptoms, signs, and computed tomographic findings. The clinical presentation and findings can be understood in terms of the effect of the dehiscence on the physiology of the labyrinth. The syndrome is a treatable cause of vestibular disturbance.