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Cystic meningioma

Dr Frank Gaillard et al.

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 common (up to 8 - 23% of cases). They are over-represented in male patients and the paediatric population ¹.

Clinical presentation

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

Classification

Nauta et al divided cystic meningiomas into 4 subtypes according to the location of the cyst with respect to the brain and meningioma ³:

type 1 : intratumoral cyst(s), located centrally within the meningioma
type 2 : intratumoral cyst(s), located peripherally within the meningioma but still surrounded by tumour
type 3 : cyst(s) located within the adjacent brain
type 4 : cyst(s) located between the meningioma and brain (arachnoid cyst)

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

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

Radiographic features

The tumour itself has imaging features identical to non-cystic meningiomas (see meningioma article for a full discussion). The cysts are of variable size and can be entirely surrounded by tumour (types 1 or 2) or clearly between tumour and brain (type 4) or within the adjacent brain (type 3). On imaging it is sometimes difficult to distinguish between these types.

Differential diagnosis

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