Superior canal dehiscence: can we predict the diagnosis?

OBJECTIVE

Identify independent clinical and audiometric factors to predict a positive high-resolution computed tomography (HRCT) scan for superior canal dehiscence (SCD).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Patients presenting SCD.

INTERVENTION(S): Audiogram, VEMP, temporal bone HRCT, and SCD symptoms and signs chart.

MAIN OUTCOME MEASURE(S): ABG, VEMP threshold, and symptoms and signs.

RESULTS

Approximately 106 patients with SCD symptoms were included: 62 had a positive and 44 had a negative CT scan. The positive scan group showed a higher average of cochlear symptoms than the negative CT scan group (4.3 versus 2.6) (p < 0.001), but no statistical difference for vestibular symptoms (2.2 versus 1.8) was identified. CVEMP thresholds of the positive and negative CT scan groups were of 66 and 81 dB, respectively (p < 0.001). The positive CT scan group showed higher ABGs at 250 Hz (24 versus 14 dB) and 500 Hz (17 versus 8 dB) (p = 0.008 and p = 0.008, resectively). No statistical significance was found when comparing both groups for air and bone conduction thresholds. Approximately 23% of the positive CT scan group showed a Valsalva-induced vertigo against 2.3% of the negative scan group (p = 0.003); 27% of the positive CT scan group showed speculum-induced vertigo but none of the negative scan patients (p < 0.001). Using logistic regression, we found that each 10-dB unit increase in the 250 Hz ABG is associated to an increase odd of having SCD of 51% (OR, 1.51; 95% CI, 1.10-2.08).

CONCLUSION

Nature and number of cochlear symptoms, Valsalva and pneumatic speculum-induced vertigo, VEMP thresholds, and ABGs seem to correlate with a positive HRCT. The ABG at 250 Hz is the most accurate predictor of SCD.