MRI screening of the internal auditory canal: Is gadolinium necessary to detect intralabyrinthine schwannomas?

Objective: Non-contrast MRI of the internal auditory canal (IAC) using high-resolution T2WI (T2 weighted image) has been proposed as the primary screening study in patients with sudden or asymmetric sensorineural hearing loss (ASNHL). However, there are concerns that non-contrast MRI may not detect labyrinthine pathology, specifically intralabyrinthine schwannomas (ILSs). The purpose of this study was to determine if non-contrast high-resolution T2WI alone are adequate to exclude these uncommon intralabyrinthine tumors. Methods: 31 patients with ILSs and 36 patients without inner ear pathology that had dedicated MRI of the IAC performed with both non-contrast T2WI and post-contrast T1WI (T1 weighted image) were identified. Three board-certified neuroradiologists reviewed only the T2WI from these 67 cases. When an ILS was identified, its location and size were recorded. Sensitivity, specificity, and accuracy were calculated using the post-contrast T1WI as the “gold standard.” A consensus review of cases with discordant results was conducted. Results: The sensitivity, specificity, and accuracy were 1.0, 1.0, and 1.0 for Observer 1; 0.84, 1.0, and 0.96 for Observer 2; 0.90, 1.0, and 0.98 for Observer 3. The 5 ILSs with discordant results were correctly identified upon consensus review. The median size of the ILSs was 4.4 mm (± 2.9 mm) and most (18/31) were intracochlear in location. Conclusion: Non-contrast high-resolution T2WI alone can detect ILSs with 84–100% sensitivity, suggesting that gadolinium may be unnecessary to exclude ILSs on screening MRI. These findings have implications for reducing cost, time, and adverse events associated with gadolinium administration in patients presenting with sudden or ASNHL. Level of evidence: 4