Meningioma MRI
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Magnetic resonance imaging (MRI): An MRI uses magnetic fields but it is a different type of image than what is produced by computed tomography (CT) and produces detailed images of the body. Like computed tomography (CT), a contrast agent may be injected into a patient’s vein to create a better picture. It is a very valuable test for meningioma.
MRI
Meningiomas are readily visualized on MRI with gadolinium attributed to the fact that meningiomas are extra axial and vascularized.
MRI
As is the case with most other intracranial pathology, MRI is the investigation of choice for the diagnosis and characterisation of meningiomas. When appearance and location is typical, the diagnosis can be made with a very high degree of certainty. In many instances however the appearances are atypical.
Meningiomas typically appear as extra-axial masses with a broad dural base. They are usually homogeneous and well circumscribed, although many variants are encountered.
Signal characteristics include:
T1
isointense: ~60-90% 3,8, 13
somewhat hypointense: 10-40% compared to grey matter
T1 C+ (Gd): usually intense and homogeneous enhancement
T2
isointense: ~50% 3,8,13
hyperintense: 35-40%
usually correlates with soft textures and hypervascular tumours 13
very hyperintense lesions may represent the microcystic variant 12
hypointense: 10-15% compared to grey matter and usually correlates with harder texture and more fibrous and calcified contents
DWI: atypical and malignant subtypes may show greater than expected restricted diffusion although recent work suggests that this is not useful in prospectively predicting histological grade 15-16
MR spectroscopy: Usually it does not play a significant role in diagnosis but can help distinguish meningiomas from mimics. Features include:
increase in alanine (1.3-1.5 ppm)
increased glutamine/glutamate
increased choline (Cho): cellular tumour
absent or significantly reduced N-acetylaspartate (NAA): non-neuronal origin
absent or significantly reduced creatine (Cr)
MR perfusion: it has good correlation between volume transfer constant (k-trans) and histological grade
Helpful signs include
CSF vascular cleft sign, which is not specific for meningioma, but helps establish the mass to be extra-axial; loss of this can be seen in grade II and grade III which may suggest brain parenchyma invasion dural tail seen in 60-72% 2 (note that a dural tail is also seen in other processes) sunburst or spokewheel appearance of the vessels
Meningiomas typically narrow arteries which they encase. This is a useful sign to distinguish a meningioma from a pituitary macroadenoma which will not.
Oedema can be seen and correlates with size, rapid growth, location (convexity and parasagittal > elsewhere), and invasion in the case of malignant meningiomas.