MENINGIOMA
X) Imaging
- CT scan kepala
* non-contrast: brain slightly hyperdense to normal brain, calcification, variable adjacent oedema
* post-contrast: brightly and homogeneously contrast enhance, malignant or cystic variants demonstrate more heterogeneity/less intense enhancement, hyperostosis (typical for meningiomas on the base of the skull)
* lytic/destructive regions are seen particularly in higher grade tumours but should make one suspect alternative pathology (e.g. haemangiopericytoma or metastasis)
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 are typical, the diagnosis can be made with a very high degree of certainty. In some instances, however, the appearances are atypical and careful interpretation is needed to make a correct preoperative diagnosis.
Meningiomas typically appear as extra-axial masses with a broad dural base. They are usually homogeneous and well-circumscribed, although many variants are encountered. It seems that the signal intensity of meningiomas on T2-weighted images correlates with the histological subtypes 27.
Signal characteristics
Signal characteristics of typical meningiomas include:
* T1
* usually isointense to grey matter (60-90%) 3,8,13
* hypointense to grey matter (10-40%): particularly fibrous, psammomatous variants
* T1 C+ (Gd): usually intense and homogeneous enhancement
* T2
* usually isointense to grey matter (~50%) 3,8,13
* hyperintense to grey matter (35-40%)
* usually correlates with a soft texture and hypervascular tumours 13
* seen in microcystic, secretory, cartilaginous (metaplastic), chordoid and angiomatous variants 12
* hypointense to grey matter (10-15%): compared to grey matter and usually correlates with harder texture and more fibrous and calcified contents
* DWI/ADC: grade 2 and 3 tumours may show greater than expected restricted diffusion although this is not universally useful in prospectively predicting histological grade 14,15
* MR spectroscopy: usually 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: good correlation between volume transfer constant (k-trans) and histological grade 26
* MR tractography: allows the identification of white matter tracts adjacent to the meningioma
* this may aid in preoperative planning for meningioma resection by allowing planning of a safer access route that would result in less residual functional iatrogenic deficits 28
Helpful imaging signs
A number of helpful imaging signs have been described, including:
* CSF 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 is seen in 60-72% 2 (note that a dural tail is also seen in other processes)
* sunburst or spoke-wheel appearance of the vessels
* white matter buckling sign
- CT scan kepala
* non-contrast: brain slightly hyperdense to normal brain, calcification, variable adjacent oedema
* post-contrast: brightly and homogeneously contrast enhance, malignant or cystic variants demonstrate more heterogeneity/less intense enhancement, hyperostosis (typical for meningiomas on the base of the skull)
* lytic/destructive regions are seen particularly in higher grade tumours but should make one suspect alternative pathology (e.g. haemangiopericytoma or metastasis)
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 are typical, the diagnosis can be made with a very high degree of certainty. In some instances, however, the appearances are atypical and careful interpretation is needed to make a correct preoperative diagnosis.
Meningiomas typically appear as extra-axial masses with a broad dural base. They are usually homogeneous and well-circumscribed, although many variants are encountered. It seems that the signal intensity of meningiomas on T2-weighted images correlates with the histological subtypes 27.
Signal characteristics
Signal characteristics of typical meningiomas include:
* T1
* usually isointense to grey matter (60-90%) 3,8,13
* hypointense to grey matter (10-40%): particularly fibrous, psammomatous variants
* T1 C+ (Gd): usually intense and homogeneous enhancement
* T2
* usually isointense to grey matter (~50%) 3,8,13
* hyperintense to grey matter (35-40%)
* usually correlates with a soft texture and hypervascular tumours 13
* seen in microcystic, secretory, cartilaginous (metaplastic), chordoid and angiomatous variants 12
* hypointense to grey matter (10-15%): compared to grey matter and usually correlates with harder texture and more fibrous and calcified contents
* DWI/ADC: grade 2 and 3 tumours may show greater than expected restricted diffusion although this is not universally useful in prospectively predicting histological grade 14,15
* MR spectroscopy: usually 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: good correlation between volume transfer constant (k-trans) and histological grade 26
* MR tractography: allows the identification of white matter tracts adjacent to the meningioma
* this may aid in preoperative planning for meningioma resection by allowing planning of a safer access route that would result in less residual functional iatrogenic deficits 28
Helpful imaging signs
A number of helpful imaging signs have been described, including:
* CSF 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 is seen in 60-72% 2 (note that a dural tail is also seen in other processes)
* sunburst or spoke-wheel appearance of the vessels
* white matter buckling sign
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