cystic meningiomas

Infratentorial

benign cystic meningioma mimicking a hemangioblastoma radiologically and a pilocytic astrocytoma intraoperatively: a case report. Axial contrast-enhanced computed tomography brain scan showing a large posterior fossa cystic mass (thin black arrows) with enhancing nodule (thick black arrow) compressing 4th ventricle causing obstructive hydrocephalus.

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Infratentorial

benign cystic meningioma mimicking a hemangioblastoma radiologically and a pilocytic astrocytoma intraoperatively: a case report. Contrast-enhanced T1 axial (A) and sagittal (B) magnetic resonance imaging demonstrating the extra-axial posterior fossa cystic lesion from the posterior interhemispheric fissure (black arrow) with an enhancing mural nodule (white arrow). No evidence of a dural tail was seen. Also noted were dilated 3rd and lateral ventricles.

jmedicalcasereports.biomedcentral.com • CC-by-2.0

Cystic

meningioma in an adult. The lesion is slightly hyperintense to brain parenchyma. The cystic part is isointense to CSF. Incidentally, note the presence of micro-ischemic changes.

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Cystic

meningioma in an adult. The lesion is slightly hypointense to brain parenchyma. The cystic part is noted around the lesion, as well as buckling of the white matter.

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Cystic

meningioma in an adult. There is dural thickening/enhancement.

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Cystic

meningioma in an adult. The cystic component caudal to the solid part has high signal.

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Cystic

meningioma in an adult. Contiguous image just above figure a. The cystic component in front and posteromedial to the solid part exhibits high signal.

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Cystic

meningioma in an adult. Corresponding ADC map image, where the solid part has mildly heterogeneous signal with iso- and hyperintense component. The cystic part is isointense to CSF.

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Cystic

meningioma in an adult. No evidence of "blooming" to suggest calcification or hemosiderin.

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Cystic

meningioma in an adult. There is homogeneous enhancement of the solid part.

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Cystic

meningioma in an adult. The cystic part does not enhance.

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Radiopaedia • CC-by-nc-sa 3.0 • de

The term cystic meningioma is applied to both meningiomas with intratumoral degenerative cyst formation as well as those with peritumoral arachnoid cysts or reactive intraparenchymal cysts.

They should not be confused with microcystic meningiomas, a distinct variant, in which the cysts are microscopic.

Epidemiology

True cystic meningiomas (type 1 and 2 - see below) are those with a few large central cysts and are uncommon. Those with more numerous smaller peripheral cysts are more frequent (8-23% of cases). They are over-represented in male patients and the pediatric population .

Clinical presentation

Patients present clinically in the same way as patients with non-cystic meningiomas, with either symptom related to increased intracranial pressure (ICP), focal neurology, or seizures.

Pathology

Various mechanisms have been proposed, and probably more than one is applicable depending on the location of the cysts:

degeneration or necrosis
direct secretion by meningioma
reactive changes (peripheral arachnoid cysts)

Classification

This classification was initially proposed by Nauta et al. in 1979, which was later modified by Worthington et al. in 1985, which at the time of writing (July 2016) is most widely used classification.

Nauta et al. divided cystic meningiomas into four subtypes according to the location of the cyst with respect to the brain and meningioma :

type 1: intratumoral cyst(s), located centrally within the meningioma
type 2: intratumoral cyst(s), situated peripherally within the meningioma but still surrounded by tumor
type 3: cyst wall may contain nest of tumor cells.
type 4: cyst(s) located within the adjacent brain
type 5: cyst(s) located between the meningioma and brain (arachnoid cyst)

4th type is most common.

Radiographic features

The tumor itself has imaging features identical to non-cystic meningiomas (see the meningioma main article for a full discussion). The cysts are of variable size and can be entirely surrounded by tumor (types 1 or 2) or clearly between the tumor and the brain (type 5) or within the adjacent brain (type 4). On imaging, it is sometimes difficult to distinguish between these types.

Differential diagnosis

The differential is dependent on the location of the tumor. For tumors around the base of the skull, cystic schwannomas (e.g. vestibular schwannoma, trigeminal schwannoma) are the main differential, as they share the bright contrast enhancement, and are commonly cystic when large.