Surgical Outcomes for Unilateral Superior Semicircular Canal Dehiscence with Low-Lying Tegmen Undergoing The Middle Cranial Fossa Repair

Objective: The present investigation compares the treatment response from the middle cranial fossa (MCF) repair of superior semicircular canal dehiscence (SSCD) between cases with preoperative low-lying tegmen and cases without preoperative low-lying tegmen.

Methods: We conducted a retrospective review of MCF procedures performed at a single tertiary academic institution from 2012 to 2022. Only unilateral SSCD cases were included in this study. Two investigators independently reviewed preoperative high-resolution temporal bone CT images and performed measurement of the ipsilateral tegmen on the coronal view. Following a previously developed protocol,[1] we classified the tegmen as either “low-lying” or “non-low-lying.” We built several multivariable binary logistic regression models with symptomatic resolution following surgery as the outcome variable. Control measures such as patient age, sex, dehiscence size, and prior ear surgery were also applied as covariates in the models. We also employed independent samples t-tests to compare the degree of change in audiometric pure tone average (PTA) and low frequency (500–1,000 Hz) air bone gap (ABG) between low-lying tegmen and non-low-lying tegmen cases. PTA was obtained by averaging air conduction thresholds at 500, 1,000, 2,000, and 3,000 Hz, adhering to American Academy of Otolaryngology - Head and Neck Surgery guidelines.[2]

Results: After reviewing 188 unilateral SSCD cases, we identified 58 (30.9%) low-lying tegmen cases. The average age was 50 years and 59% of patients were female. Controlling for patient age, sex, dehiscence size, and prior ear surgery status, patients with low-lying tegmen were significantly less likely to experience symptomatic resolution for headache (aOR 95% CI: 0.05–0.65, p = 0.008), disequilibrium (aOR 95% CI: 0.18–0.86, p = 0.019), dizziness (aOR 95% CI: 0.21–0.92, p = 0.028), aural fullness (aOR 95% CI: 0.09–0.62, p = 0.004), and internal amplification of sound (aOR 95% CI: 0.08–0.56, p = 0.002). The degree of change in PTA and ABG following surgery did not differ significantly between low-lying tegmen and non-low-lying tegmen cases (+1.3 ± 13.9 dB versus +3.4 ± 8.3 dB, p = 0.35; -2.2 ± 8.4 dB versus -1.8 ± 11.1 dB, p = 0.90, respectively).

Conclusions: This is the first investigation on the relationship between low-lying tegmen and surgical outcomes following the MCF approach for SSCD repair. Patients with low-lying tegmen experienced significantly less symptomatic benefit from the MCF procedure compared with patients without low-lying tegmen. However, the degree of audiometric improvement did not differ significantly between low-lying tegmen and non-low-lying tegmen cases. These findings may be important for consideration of candidate selection and counseling of patient expectations. The underlying factors accounting for our observations warrant further investigation.

Publication History

Article published online:
01 February 2023

• References

• 1 Lookabaugh S, Kelly HR, Carter MS, et al. Radiologic classification of superior canal dehiscence: implications for surgical repair. Otol Neurotol 2015;36(1):118–125
• 2 Gurgel RK, Jackler RK, Dobie RA, Popelka GR. A new standardized format for reporting hearing outcome in clinical trials. Otolaryngol Head Neck Surg 2012;147(5):803–807