DYNAMIC MRI OF MENINGIOMAS AND SCHWANNOMAS - IS DIFFERENTIAL-DIAGNOSIS POSSIBLE

We studied 23 patients with meningiomas and 14 with schwannomas using dynamic spin-echo (TRITE 200/15 ms) MRI. Histologically the meningioma s were classified according to the 1993 WHO classification Serial imag es were obtained every 30 s for 210 s after rapid injection of gadopen tetate dimeglumine (0.1 mmol/kg). The contrast-enhancement ratio (CER) was divided into three patterns; a sharp rise with a peak within 60 s (A), a relatively rapid increase with a peak between 60 and 210 a (B) , a slow increase without a peak (C). The patterns were correlated wit h the histology of the tumors. The signal intensities of the tumours o n T2-weighted images were also analyzed and correlated with the dynami c patterns. Meningiomas had more varied dynamic patterns than schwanno mas. Almost half of the meningiomas showed pattern A, and one third pa ttern C. Of six meningothelial meningiomas showed pattern A; all schwa nnomas and fibrous meningiomas showed pattern C. Various patterns were observed in transitional meningiomas. Of the a meningiomas showing pa ttern C, only one gave high signal on T2-weighted images, and could no t be differentiated from the schwannomas. Thus, one third of meningiom as could not be differentiated from schwannomas by the dynamic contras t enhancement alone. However, when this was combined with the signal i ntensity on T2-weighted images, most meningiomas could be differentiat ed from schwannomas.