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AJNR - American Journal of Neuroradiology

Published ahead of print on March 20, 2008
doi: 10.3174/ajnr.A0996

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Diffusion-Weighted MR Imaging: Diagnosing Atypical or Malignant Meningiomas and Detecting Tumor Dedifferentiation

V.A. Nagar^a, J.R. Ye^a, W.H. Ng^b, Y.H. Chan^c, F. Hui^a, C.K. Lee^b and C.C.T. Lim^a,d

^a Department of Neuroradiology, National Neuroscience Institute, Singapore
^b Neurosurgery, National Neuroscience Institute, Singapore
^c Department of Biostatistics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
^d Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore

View larger version (55K): [in this window] [in a new window]   Fig 1. Patient 34, atypical meningioma in a 73-year-old man. A, Enhanced coronal T1 image shows an en plaque meningioma (arrow) over the left frontoparietal region, with ill-defined margins. B, DW MR image demonstrates the mass to be hyperintense. C, ADC map shows decreased signal intensity compared with normal white matter (absolute ADC = 0.63 x 10–3 mm2/s; NADC ratio = 0.88).

View larger version (55K): [in this window] [in a new window]   Fig 2. Patient 18, benign meningioma in a 37-year-old woman. A, DW MR image showing the tumor in the left frontal region to be hyperintense. B, ADC map showing increased signal intensity compared with normal white matter (absolute ADC = 0.98 x 10–3 mm2/s; NADC ratio = 1.46). C, Axial T2-weighted image shows that the hyperintensity in A was probably due to T2 shinethrough effect.

View larger version (20K): [in this window] [in a new window]   Fig 3. Box and whisker plot comparing ADC values between groups. A, Absolute intratumoral ADC values in benign and atypical/malignant meningiomas showing some overlap between groups. A single outlier (patient 44) in the atypical/malignant group had a recurrent malignant meningioma of the rhabdoid variant. B, There is no overlap in NADC ratios between benign and atypical/malignant meningiomas.

View larger version (133K): [in this window] [in a new window]   Fig 4. Patient 12, right sphenoid wing meningioma in a 79-year-old man. A, Before first surgery, contrast-enhanced axial T1 image shows an extra-axial enhancing mass lesion at the right sphenoid wing causing cavernous sinus obstruction. B, Corresponding DW MR image demonstrates the mass to be isointense. C, ADC map shows isointensity (absolute ADC = 0.90 x 10–3 mm2/s; NADC ratio = 1.23). Histologic examination showed benign meningothelial meningioma. D, Follow-up contrast-enhanced axial T1-weighted image before second resection shows the recurrent mass to be more extensive. E, Corresponding DW MR image of the tumor before second resection (arrow) is now hyperintense. F, ADC map shows hypointensity (absolute ADC has decreased to 0.60 x 10–3 mm2/s, and NADC ratio decreased to 0.77). Histologic examination revealed dedifferentiation to atypical meningioma.