Magnetic resonance imaging characteristics of typical and atypical/anaplastic meningiomas - Case series and literature review.

OBJECTIVE: The histologic grades of meningiomas have a significant impact on the risk of recurrence, prognosis, and the need for adjuvant treatment such as radiation therapy. The purpose of this study is to investigate the magnetic resonance imaging (MRI) characteristics of typical and atypical/anaplastic meningiomas.

METHODS: The medical records of 32 consecutive patients who underwent meningioma resections between April 2004 and November 2006 were retrospectively reviewed. Preoperative MR studies were reviewed by board-certified neuroradiologists. Both univariate and multivariate analyses were used to analyze the MR characteristics of the typical and atypical/anaplastic meningiomas. A review of pertinent literature was also conducted.

RESULTS: Thirty-two patients were identified during the study period. Histopathologic examination of the surgical specimens revealed 27 (84.4% - Group I) typical meningiomas and 5 (15.6% - Group 2) atypical/anaplastic meningiomas. The chi-square test showed that restricted diffusion was much more likely to be present in Group 2 (p < 0.01), and the choline-to-creatinine (Cho/Cr) ratio was significantly higher in Group 2 (8.8 vs. 5.1, p = 0.01). The multivariate analysis confirmed that the atypical/anaplastic group is much more likely to have restricted diffusion (p = 0.02) and higher Cho/Cr ratios (p = 0.03).

CONCLUSION: Meningiomas with restricted diffusion and higher Cho/Cr ratio on MR spectroscopy are more likely to be atypical/anaplastic types. Preoperative MRI utilizing these sequences can provide important information which can be valuable to counsel patients regarding prognosis, risk of recurrence and the need for adjuvant radiation in addition to surgical resection.