Apparent Diffusion Coefficient Values and Intra-tumoral Susceptibility Signals in Meningiomas and Schwannomas: Useful Tools for Challenging Cases

Background: We aimed to estimate the diagnostic accuracy of apparent diffusion coefficient values (ADC) and intra-tumoral susceptibility signals (ITSS) in differentiating meningiomas and schwannomas. Methods: This retrospective study included 41 patients with 23 histopathologically proven meningiomas (20 patients with benign meningioma and 3 patients with high-grade meningioma) and 18 schwannomas. We calculated the mean ADC values and ADC ratio from ADC maps and intratumoral susceptibility signals (ITSS) in susceptibility-weighted imaging (SWI) for all patients. The quantitative variables were compared between the tumor groups using t test and the qualitative variables were compared between them using Chi-square test. Results: In this study, the mean ADC value of meningiomas (0.86±0.11×10-3 mm2 /s, range 0.67-1.04) was lower than schwannomas (1.32±0.16×10-3 mm2 /s, range 1.10-1.65) with no overlap in the range of ADC values. The mean ADC ratio of schwannomas (2.0±0.29, range 1.45- 2.58) was higher than meningiomas (1.24±0.17, range 0.83-1.64) with some overlap. We found significant difference in mean ADC value and ADC ratio between meningiomas and schwannomas. The presence of intratumoral microhemorrhages (ITSS-H) in SWI was more suggestive of schwannomas and the presence of calcification was in favor of benign meningiomas. We did not find any significant difference in mean ADC value and ADC ratio between benign and high-grade meningiomas with considerable overlap in their range. Conclusion: Additional magnetic resonance imaging findings such as ADC values and ITSS in SWI can help better pre-operative diagnosis of meningiomas and schwannomas, particularly in challenging patients.