The contribution of diffusion-weighted MR imaging to distinguishing typical from atypical meningiomas

Introduction: Atypical/malignant meningiomas recur more frequently then typical meningiomas. In this study, the contribution of diffusion-weighted MR imaging to the differentiation of atypical/malignant and typical meningiomas and to the determination of histological subtypes of typical meningiomas was investigated. Methods: The study was performed prospectively on 39 patients. The signal intensity of the lesions was evaluated on trace and apparent diffusion coefficient (ADC) images. ADC values were measured in the lesions and peritumoral edema. Student's t-test was used for statistical analysis. P < 0.05 was considered statistically significant. Results: Mean ADC values in atypical/malignant and typical meningiomas were 0.75 +/- 0.21 and 1.17 +/- 0.21, respectively. Mean ADC values for subtypes of typical meningiomas were as follows: meningothelial, 1.09 +/- 0.20; transitional, 1.19 +/- 0.07; fibroblastic, 1.29 +/- 0.28; and angiomatous, 1.48 +/- 0.10. Normal white matter was 0.91 +/- 0.10. ADC values of typical meningiomas and atypical/malignant meningiomas significantly differed (P < 0.001). However, the difference between peritumoral edema ADC values was not significant (P > 0.05). Furthermore, the difference between the subtypes of typical meningiomas and atypical/malignant meningiomas was significant (P < 0.001). Conclusion: Diffusion-weighted MR imaging findings of atypical/malignant meningiomas and typical meningiomas differ. Atypical/malignant meningiomas have lower intratumoral ADC values than typical meningiomas. Mean ADC values for peritumoral edema do not differ between typical and atypical meningiomas.