An unusual case of intracranial meningioma appearing as cystic lesion with nodule within

A 67-year-old male patient presented with gradually increasing headache for 2 weeks. He is a hypertensive patient well controlled with medications. No other co-morbidities noted.

Axial NCCT of head revealed a large cyst with an iso-hyperdense peripherally placed nodule within in the right frontoparietal lobe with mild perilesional oedema. Few isodense septations are noted within.

MRI brain revealed a large cyst (6.2(ap) x5.4(cc) x 4.2(tr) cm) with a well defined peripherally placed nodule within in the right frontoparietal lobe. The nodule is isointense on T1 and T2 weighted images. Few isointense septations were noted within the cyst. Perilesional oedema was seen in right frontal and parietal lobe. Underlying mass effect with midline shift of 3.6 mm to the left side is noted without any underlying brain parenchymal infiltration. No hyperostosis of the overlying calvarium is noted. There is no restriction on DWI. No blooming foci on GRE images.

CEMRI images reveal intense homogeneous enhancement of solid nodule along with incomplete enhancement of the cyst wall and few septations within. There is enhancement of the dura overlying the nodule.

Meningiomas are the most common primary non-glial intracranial neoplasms, contributing to about one-third of all central nervous system (CNS) tumours and about 16 to 20% of all intracranial neoplasms. [1,2,3,4]. Due to its relatively common occurrence, classical location and presence of typical findings on computed tomography (CT) and magnetic resonance imaging (MRI) the diagnosis of meningioma are relatively straight forward. [1][4]. However, there are numerous other subtypes of meningioma having a myriad of imaging features that make their diagnosis tricky.[1][3].

One such feature is the presence of cyst associated with meningiomas. Cystic meningiomas are relatively rare entities. [5]. Cystic meningiomas may be intra-tumoral cavities and extra-tumoral or arachnoid cysts. Therefore, the cysts can be located within the tumour mass, either centrally or eccentrically; outside and adjacent to the edge of the tumour or occasionally inside the adjacent brain parenchyma.[3][6]. Cystic changes in meningiomas were initially classified into four types by  Nauta et.al.[7] A fifth type was subsequently put forward by Worthington et al. [6], which was later histologically correlated[8]

Type 1: Intra-tumoral cyst centrally located within the meningioma.
Type 2: Intra-tumoral cyst peripherally located within the meningioma surrounded by tumor.
Type 3: Cyst within brain adjacent to tumour, wall formed by arachnoid (wall does not show enhancement on imaging)
Type 4: Cyst between tumour and adjacent brain (entrapped CSF)
Type 5: Cyst wall with nest of tumour cells, wall formed by tumour cells (wall shows enhancement on imaging)

In our case, there is a mixed solid -cystic lesion with incomplete septations which on post-contrast scan reveals homogenous enhancement of the solid component and incomplete enhancement of the cyst wall and few septations within. There is also enhancement of the dura overlying the nodule. We had cystic meningioma among our differential diagnosis because of the dural and cyst wall enhancement. Surgery was done and the tumour resected which revealed the diagnosis of WHO grade II meningioma with cystic changes.

So although uncommon meningioma should be part of the differential diagnosis in case of cyst with nodule patterns of intracranial lesions. The images should be carefully scrutinized for Dural enhancement on post-contrast images.

Written consent has been obtained from the patient