Objective: To study the behavior of meningiomas in diffusion-weighted sequences and the correlation of these findings with the histological findings.
Material and methods: We prospectively included all patients operated on for meningiomas at our hospital during two years. We studied 30 meningiomas in 28 patients aged 31 to 85 years old. All patients underwent MRI prior to surgery, including diffusion-weighted sequences, in a 1.5 T scanner. We evaluated the signal intensity in T2-weighted images, diffusion-weighted images (b=1,000), and apparent diffusion coefficient (ADC) maps within the tumor and in the parietal white matter as a reference. In the histological study, cellularity, proliferation index, histological grade, and cerebral invasion were evaluated.
Results: Of the 30 meningiomas, 22 were World Health Organization (WHO) grade I and 8 were atypical or WHO grade II. The overall mean value of the ADC was 89.19+/-13.95x10(-3) mm2/s; the mean ADC value was 82+/-13.69x10(-3) mm2/s in the atypical group and 92.21+/-13.21x10(-3) mm2/s in the typical group. No statistically significant differences were found between the 2 groups. Two subtypes of typical meningiomas, secretory and angiomatous meningiomas, had the highest values in the ADC maps. In the histological analysis, there was a significant association between tumor cellularity and the signal in the ADC map.
Conclusion: Meningiomas show moderately restricted diffusion. The signal on the ADC map is associated with tumor cellularity but we have not demonstrated its usefulness for predicting the histological grade.