Intraoperative Electrocochleography Correlates to Outcomes in Transmastoid and Middle Cranial Fossa Superior Semicircular Canal Dehiscence Repair

Electrocochleography in the diagnosis of third window conditions

Introduction

Superior semicircular canal dehiscence (SSCD) is the best-known and most common presentation of so-called "third window conditions." There are a variety of diagnostic measures and tests for this condition in the current literature, including air-bone gap, vestibular-evoked myogenic potentials, and electrocochleography (EcochG). The purpose of this study was to investigate the diagnostic utility of EcochG and its relationship to air-bone gap in a cohort of patients with confirmed SSCD.

Methods

We reviewed data from 20 patients (11 female and 9 male subjects, age ranging 21-78 years), with confirmed unilateral or bilateral superior canal dehiscence. In total, 11 patients had unilateral SSCD and 9 patients had bilateral SSCD as determined by high-resolution CT scan. This resulted in the inclusion of twenty-nine ears with superior canal dehiscence and 11 normal ears.

Results

Our results indicated that all confirmed SSCD ears presented with an abnormal EcochG SP/AP value and that there was a statistically significant difference between normal and dehiscent ears. There was no statistically significant relationship between air-bone gap and SP/AP ratio in the ears diagnosed with SSCD nor was there a significant difference between dehiscent and normal ears in terms of air-bone gap at three frequencies.

Discussion

These results are consistent with previous studies showing the diagnostic utility of EcochG for this condition and the variability of air-bone gap. While an unexpected air-bone gap continues to be a red flag for SSCD, its absence along with the presence of subjective symptoms is a reasonable indicator for further clinical investigation to include EcochG.

Development of semicircular canal occlusion

Surgical treatment of vertigo is performed with in-depth study of inner ear diseases. Achieving an effective control of vertigo symptoms while reducing damage to hearing and reducing surgical complications is the principle followed by scholars studying surgical modalities. Semicircular canal occlusion is aimed at treatment of partial peripheral vertigo disease and has attracted the attention of scholars because of the above advantages. This article provides a review of the origins of semicircular canal occlusion, related basic research, clinical applications, and the effects of surgery on vestibular and hearing function.