Learning Objectives:

Introduction: Semicircular canal dehiscence syndrome (SCDS) is caused by a bony defect of the superior semicircular canal, resulting in autophony, bone conduction of bodily sounds and pseudo conductive hearing loss. Vestibular manifestations include sound- or pressure-evoked vertigo. cVEMP (cervical vestibular evoked myogenic potential) testing is used as the diagnostic gold standard in addition to CT scanning. The aim was determine the pre and post-operative cVEMP changes in patients undergoing transmastoid occlusion surgery for SCDS.

Methods: All patients suggestive of SCDS underwent CT scanning and cVEMP testing. All those with positive findings for both (dehiscent superior canal and asymmetrical cVEMP thresholds >35%) then underwent surgery. cVEMP thresholds were measured 3 months post-operatively in a standardised manner. Asymmetry between ears was assessed by means of the Jonkees formula and diagnostic of SCDS when greater than 35%. Data was identified and collated retrospectively.

Results: Twenty patients, with 22 affected ears underwent surgical occlusion with pre-operative and post-operative cVEMP testing. All patients with unilateral SCDS had asymmetrical cVEMP thresholds >35% with a mean of 164% (N = 14, SD 224). In the 17 ears with recordable cVEMPS, all demonstrated normalisation of thresholds except in one, who had persistent symptoms and BPPV. In 10 out of 12 unilaterally affected patients, the postoperative cVEMP threshold was less than or equal to the contralateral ear. In two patients there were no recordable thresholds in the contralateral ear.

Conclusion: cVEMP testing continues to be a valuable assessment tool in patients with symptoms suggestive of SCDS. Our results show that with the transmastoid occlusion technique, the post-operative cVEMPs return to normal (as compared with their contralateral side) in the majority of cases.