Coexistence of Dural and Intraventricular Meningioma-A Rare Entity

Meningioma is a commonly encountered solitary, benign, intracranial, extra-axial tumor in day-to-day brain imaging. Majority are dural-based located commonly at the cerebral convexities. Uncommonly, they are multiple or may be seen in intraventricular location. Coexisting dural and intraventricular meningioma is an exceedingly rare entity. It may be difficult to differentiate them from metastases. Hence through this case report, we attempt to describe this rare entity with its differentiation from similar-appearing lesions.


Introduction
Meningiomas are extra-axial tumors that are majorly benign and constitute nearly one-quarter of all intracranial tumors [1].
They are categorized in to Grade I (benign), Grade II (atypical) and Grade III (anaplastic) according to World Health Organisation Classification 2016 [2]. Atypical meningiomas constitute up to one-third of all meningiomas [3]. Multifocal meningiomas are uncommon occurring in less than a tenth of meningioma cases [4].
Meningioma occurring within the ventricular system are very rare comprising of only 0.5-3.7% cases of meningioma epic entered primarily in the lateral ventricles especially the trigone arising from the tela choroidae and choroid plexus stroma [5,6]. Very few case reports of atypical and anaplastic intraventricular meningioma exist in medical literature [5][6][7][8][9]. Hence in this case report, we describe a rare coexistence of dural and intraventricular, atypical meningiomas preoperatively diagnosed on imaging.

Case Report
A 65year old man with history of chronic headache since more than nine months came for a magnetic resonance imaging (MRI) of the brain to exclude organic lesion. Routine laboratory tests including those in blood and urine were unremarkable. MRI brain

Discussion
The incidence of meningioma is apparently rising not only due to improved and extensive neuroimaging but also due to increased proportion of the elderly population where it has the common occurrence [10]. The higher incidence of meningioma in adult females reported in recent literature in contrast to previous reports of male preponderance is highly attributed to various reproductive and hormonal factors [11]. Arachnoid cap cells are the usual sites for origin of most meningiomas with majority being benign. Less percentage of meningioma show signs of malignancy like marked vascularity; lack of internal organoid architecture; higher percentage of mitotic figures, nuclear pleomorphism; disproportionately large nucleolus, focal necrosis and infiltration in to brain parenchyma along with variable expression of Ki-67, a marker for tumor recurrence in atypical and anaplastic meningiomas [10,12,13].
There are increasing reports of benign, multiple meningiomas in recent literature which account for nearly one-tenth of all cases [4,14]. Tumor cell spread by CSF or hematogenous dissemination is the most widely accepted mechanism making two different sporadic forms in one patient very rare [10]. Previous reports have revealed atypical with psammomatous and fibrous with anaplastic meningiomas [10,15,16]. But ours is probably the first report of double atypical meningioma, one dural and another intraventricular in location. Also, very few reports of atypical intraventricular meningioma exist in the literature [17]. Atypical meningioma shows progression to anaplastic meningioma within a short period of time [17]. Very rarely meningioma may occur in intraparenchymal location within the cortex where the absence of dural tail may make it difficult to distinguish it from high-grade glioma, cavernoma angioma, metastases and sarcoma [18].
Multiple meningioma may rarely present as bipolar disorder like psychiatric illness making imaging mandatory to rule out organic lesion prior to targeted medical management of bipolar psychotic illness [19]. Multiple dural-based meningioma also forms a differential diagnosis of multiple dural-based metastases [20]. Classical benign meningioma appears as a homogeneous, round to ovoid, dural-based, extra-axial lesion with sharp margins, internal calcification and near-homogeneous postcontrast enhancement with or without bone reaction. Atypical radiological features include intra-tumoral heterogeneity, presence of internal hemorrhage or necrosis, venous sinus invasion, lack of tumor capsule enhancement, indistinct tumor-brain interface, diffusion restriction, increased Ktrans on dynamic contrast MR examination and peritumoral edema with delayed increased vascularity causing significant mass effect [21,22]. High and low-intensity large areas corresponding to internal hemorrhage and necrosis respectively along with non-spheroid shape, significant calcification and bone destruction are signs of high-grade meningioma [21,22].