Differentiation Between Intralabyrinthine Schwannoma and Contrast-enhancing Labyrinthitis on MRI: Quantitative Analysis of Signal Intensity Characteristics.

Abstract

Distinguishing intralabyrinthine schwannoma (ILS) from labyrinthitis is crucial in deciding patient management between surgery and medication; however, the clinical and radiological differentiation between ILS and labyrinthitis is difficult, especially when labyrinthitis shows contrast-enhancement mimicking ILS on magnetic resonance imaging (MRI). This study aimed to evaluate the quantitative characteristics of signal intensity on 3T MRI for differentiating ILS from contrast-enhancing labyrinthitis (CEL). Retrospective study. Tertiary referral center. Between July 2003 and June 2017, 9 subjects diagnosed with ILS (16 MRI cases) and 9 subjects diagnosed with CEL (9 MRI cases) were enrolled in the study. Normalized signal intensity on contrast-enhanced T1-weighted image (nCE-T1), normalized signal intensity on T2-weighted image (nT2), and normalized signal intensity on contrast-enhanced fluid-attenuated inversion recovery image (nFLAIR) were measured and compared between ILS and CEL. The diagnostic performance of these values was assessed using receiver operating characteristic (ROC) analysis. In ILS, the nCE-T1 and the nT2 were significantly higher and lower, respectively, than in CEL (all, p < 0.05); and the nFLAIR did not significantly differ (p > 0.05). The maximal nCE-T1 achieved the highest area under the curve (AUC) in differentiating ILS and CEL, followed by the mean nCE-T1, the mean nT2, and the maximal nT2. Combination of the nCE-T1 and the nT2 showed higher AUC than the nCE-T1 alone, but without statistical significance (p = 0.340). Quantitative measurement of the signal intensity on MRI can be a viable imaging tool for differentiating ILS from CEL.