Magnetic resonance imaging for intracranial meningioma diagnosis
Contrast-enhanced magnetic resonance imaging (MRI) is the imaging modality routinely used to follow up patients who have undergone surgical resection of brain meningiomas. There are growing concerns about the massive use of gadolinium-based contrast agents (GBCA). Our aim was to evaluate the performance of a new imaging protocol, performed without GBCA injection, in the detection of tumoral residue or local recurrence after surgery of parafalcine and convexity meningiomas.
Materials and methods: Only adult patients with a documented resected parafalcine or convexity meningioma were included. We performed a dedicated MRI protocol that included non-contrast and post-contrast sequences. The presence or absence of residue on the unenhanced sequences was independently recorded by three observers: first blindly, then in comparison with a baseline enhanced MRI examination.
Results: A total of 51 patients were included. 37 of them featured a tumor residue on the reference enhanced sequence. Overall, an average of 32 of 37 (87%) residues were identified on the unenhanced sequences that were blindly reviewed; and more than 34 of 37 (93%) were identified with the help of the comparative baseline enhanced examination, with a high sensitivity. The missed cases were related to small residues.
Conclusion: Unenhanced MRI sequences are highly sensitive and specific in identifying a tumor residue or a local recurrence in the post operative follow up of brain meningiomas. Sensitivity is even higher with the help of a comparative baseline enhanced MRI examination, whatever the strength of magnetic field 1).
Occasionally may be isointense with brain on T1WI and T2WI, but most enhance with gadolinium. Brain edema may or may not be present. Calcifications appear as signal voids on MRI. Gives information regarding patency of dural venous sinuses (accuracy in predicting sinus involvement is ≈ 90%25). “Dural tail sign” is a common finding.
MR imaging findings include a tumor which is dural-based and isointense with gray matter, demonstrates prominent and homogeneous enhancement (> 95%), frequent cerebrospinal fluid/vascular cleft(s), and often an enhancing dural tail (60%).
Intracranial meningiomas usually show heterogeneous low signal on T1- and high signal on T2-weighted and FLAIR images.
The frontal and parietal lobes are commonly affected. In addition, brain edema, dural tail sign and bone infiltration are the most frequent associated findings 2).
Approximately 10 to 15% of meningiomas have an atypical appearance on MR images, mimicking metastases or malignant gliomas 3).
In particular, secretory meningiomas may have a significant amount of peritumoral edema 4).
A 68-year-old patient who had been under study for resting tremor for less than a year.
Large left frontal extraaxial lesion with a maximum diameter of 4.1 x 2.9 x 3.5 cm (AP x T x CC) with significant contrast enhancement and an associated dural tail sign. It causes a mass effect on the left frontal lobe with mild edema. Posterior to this lesion there is a relatively extensive pseudonodular thickening of the left pachymeninge of at least 3 cm in craniocaudal diameter, 2.2 anteroposterior and with a maximum thickness of 8 cm.
Volumetric measurement
Diffusion tensor magnetic resonance imaging
Romani et al., prospectively studied 110 meningioma patients operated on in a single center from March 1st to the 25th of May 2012. Demographic data, location and size of the tumor, peritumoral edema, T1 weighted image, T2 weighted image, proton density weighted (PDWI), fluid-attenuated inversion recover (FLAIR) sequences, and arterial spin labeling (ASL) perfusion were studied and compared with the gray matter signal to predict meningioma consistency. Diffusion tensor imaging (DTI) with fractional anisotropy (FA) and mean diffusivity (MD) maps were included in the preoperative MRI. Meningioma consistency was evaluated by the operating surgeon who was unaware of the neuroradiological findings.
In univariate analysis, meningioma size (diameter > 2 cm) and supratentorial or sphenoidal wing location were more frequently associated with hard-consistency meningiomas (p < 0.05). In addition, isointense signal on MD maps (p = 0.009), hyperintense signal on FA maps, and FA value > 0.3 (p = 0.00001) were associated with hard-consistency tumors. Age and sex, T1WI, T2 weighted image, PDWI, FLAIR, or ASL perfusion sequences and peritumoral edema were not significantly associated with meningioma consistency. In logistic regression analysis, the most accurate model (AUC: 0.9459) for predicting a hard-consistency meningioma shows that an isointense signal in MD-maps, a hyperintense signal in FA-maps, and an FA value of more than 0.3 have a significant predictive value.
FA value and MD and FA maps are useful for prediction of meningioma consistency and, therefore, may be considered in the preoperative routine MRI examination of all patients with intracranial meningiomas 5).
Arterial spin labelled imaging (ASL)
Tumor vascularity can now be determined using arterial spin labeling and Dynamic Susceptibility Weighted Contrast-Enhanced Perfusion Imaging, allowing the neurosurgeon or neurointerventionalist to assess patient candidacy for Preoperative embolization of intracranial meningioma 6)
ASL-PWI may provide a reliable and noninvasive means of predicting angiographic vascularity of meningiomas. It may thus assist in selecting potential candidates for preoperative digital subtraction angiography and embolization in clinical practice 7).