Hearing Outcomes After Surgical Plugging of the Superior Semicircular Canal by a Middle Cranial Fossa Approach

Abstract

To determine postoperative hearing outcomes after surgical plugging via middle cranial fossa approach for superior semicircular canal dehiscence syndrome (SCDS). Clinical review. Tertiary care medical center. Forty-three cases of SCDS based on history, physical examination, vestibular function testing, and computed tomography imaging confirming the presence of a dehiscence. All patients underwent surgical plugging of the superior semicircular canal via middle cranial fossa approach. Pure tone audiometry was performed preoperatively and at 7 days and at least 1 month postoperatively. Change in air-bone gap (ABG) and pure tone average (PTA). Preoperative average ABG across 0.25, 0.5, 1, and 2 kHz was 16.0 dB (standard deviation [SD], 7.5 dB). At 7 days postoperatively, average ABG was 16.5 dB (SD, 11.1; p = 0.42), and at greater than 1 month was 8.1 dB (SD, 8.4; p < 0.001). 53% (95% confidence interval, 33-69) of affected ears had greater than 10 dB increase in their 4-frequency (0.5, 1, 2, and 4 kHz) PTA measured by bone-conduction (BC) threshold 7 days postoperatively and 25% (95% confidence interval, 8-39) at greater than 1 month postoperatively. Mean BC PTA of affected ears was 8.4 dB hearing loss (HL) (SD, 10.4) preoperatively. Compared with baseline, this declined to 19.2 dB HL (SD, 12.6; p < 0.001) at 7 days postoperatively and 16.4 dB HL (SD, 18.8; p = 0.01) at greater than 1 month. No significant differences in speech discrimination score were noted (F = 0.17). Low-frequency air-bone gap decreases after surgical plugging and seems to be due to both increased BC thresholds and decreased AC thresholds. Surgical plugging via a middle cranial fossa approach in SCDS is associated with mild high-frequency sensorineural hearing loss that persists in 25% but no change in speech discrimination.