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

OBJECTIVE: 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).

STUDY DESIGN: Retrospective study.

SETTING: Tertiary referral center.

PATIENTS: 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.

MAIN OUTCOME MEASURES: 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.

RESULTS: 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).

CONCLUSIONS: Quantitative measurement of the signal intensity on MRI can be a viable imaging tool for differentiating ILS from CEL.