Cystic meningioma is a rare form of intracranial meningioma. Meningiomas are typically solid tumors but may rarely have cystic components. The diagnosis of cystic meningioma is clinically challenging as the finding of multiple intra-axial tumors, including metastatic tumors, is relatively common.
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.
Those with more numerous smaller peripheral cysts are more frequent (8-23% of cases). They are over-represented in male patients and the paediatric population
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.
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)
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 tumour
type 3: cyst(s) located within the adjacent brain
type 4: cyst(s) located between the meningioma and brain (arachnoid cyst)
Cystic meningioma is not easy to diagnose preoperatively and is often misdiagnosed as a cystic glioma or metastatic brain tumor.
The tumour 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 tumour (types 1 or 2) or clearly between the tumour and the brain (type 4) or within the adjacent brain (type 3). On imaging, it is sometimes difficult to distinguish between these types.
The differential is dependent on the location of the tumour. For tumours around the base of the 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.
CT whole-brain perfusion (CTP). 4D-CTA showed the arterial supply feeding the tumor and late enhancement of the tumor nodule, similar to that seen in meningioma by conventional angiography. CTP showed that the tumor had a higher cerebral blood flow and cerebral blood volume and a longer mean transit time than adjacent brain tissue. These findings were consistent with meningioma and reinforced the other imaging findings, resulting in the correct preoperative diagnosis. The new techniques available for 320-row CT can potentially be used to improve differential diagnosis and preoperative assessment of cystic tumors with nodules 4).
A retrospective analysis of 13 patients (mean age: 49.9 years) who underwent surgical resection of intracranial cystic meningiomas from January 2006 to February 2014. There were 5 male and 8 female patients. The Glasgow Outcome Scale was used to assess the clinical outcome at 6 months. Results. Headache was the main presenting clinical feature. Most of the tumours were located on the right side. The frontal convexity was the most common site. Gross total resection was performed in 10 patients. The most common histopathological type was meningothelial variety. Conclusion. Intracranial cystic meningiomas are usually benign that occur in relatively young patients. Resection of cysts that show contrast enhancement is essential to reduce recurrence 5).
Ramanathan et al. report a case of cystic meningioma initially diagnosed as a metastatic tumor from a recurrence of acute lymphoid leukemia. However, postoperative histopathological examination demonstrated an atypical meningioma 6).