MRI of the Internal Auditory Canal: Is Gadolinium Necessary to Detect Intralabyrinthine Schwannomas?

Objectives Noncontrast MRI of the internal auditory canal (IAC) using high-resolution T2-weighted image (T2WI) has been proposed as the primary screening study in patients with sudden or asymmetric sensorineural hearing loss (ASNHL). However, there are concerns that noncontrast MRI may not detect labyrinthine pathology, specifically intralabyrinthine schwannomas (ILSs). The purpose of this study was to determine if noncontrast high-resolution T2WI alone are adequate to exclude these uncommon intralabyrinthine tumors.

Methods Thirty-one patients with ILSs and 36 patients without inner ear pathology that had dedicated MRI of the IAC performed with both noncontrast T2WI and postcontrast T1-weighted image (T1WI) 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 postcontrast 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; and 0.90, 1.0, and 0.98 for Observer 3. The five 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 out of 31) were intracochlear in location.

Conclusion Noncontrast high-resolution T2WI alone can detect ILSs with 84 to 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.