Atypical intraventricular meningioma in an adult female

A 50-year-old woman presented with history of acute exacerbation of chronic headache and gradually progressive weakness of left upper and lower limbs of 2 weeks duration. Neurologic evaluation reveals reduced power (3/5) in left upper limb and left lower limb, exaggerated left sided deep tendon reflexes and papilledema.

Plain CT head showed an ill-defined lobulated hyperdense lesion in relation to trigone of right lateral ventricle with intraventricular and intraparenchymal components with mass effect in the form of mild line shift and upstream hydrocephalus.There was no calcification within the lesion and the calvarium appeared normal.

MRI-Brain(P+C) showed a lobulated heterogeneously enhancing lesion epicentered in the lateral wall of atrium of right lateral ventricle with intraventricular and intra parenchymal extensions involving right parieto occipital lobes with perilesional white matter edema.There was significant mass effect in the form of midline shift to left,compression of brain stem and posterior third ventricle resulting in upstream hydrocephalus.It also showed a small curvilinear area of diffusion restriction in the right lateral most aspect of the lesion with peripheral flow voids.MRS: Ch/Cr ratio 2.6, choline NAA ratio 6.5 and absent NAA levels.Dynamic contrast enhanced perfusion revealed rCBV of 14- 16 and PSR (percentage signal recovery) of <50%.

Meningiomas comprise 14-19% of all intracranial tumors. Of all meningiomas, those with intraventricular location (without an attachment of the meningioma to the dura) are rare entities, comprising only 0.5-5%(1). Most intraventricular meningiomas are low grade. Of all meningiomas, atypical and malignant meningioma account for 4.7-19.8% and 1-7.2% respectively and intraventricular meningioma comprise 0.5-3.7% of intra cranial meningioma. Therefore, intraventricular non-benign meningiomas are considered to be less than 1% of intra cranial meningioma. In addition, the incidence of non-benign meningiomas is higher in young patients (2).

The clinical presentation is usually due to mass effect, either by direct compression of the adjacent brain or from obstruction to normal CSF drainage with resultant hydrocephalus (4). Intraventricular meningioma is thought to arise from meningothelial inclusion bodies located in the teal choroidea and/or mesenchymal stroma of the choroid plexus. (5)The most frequent site is the trigone of lateral ventricles (1).

The CT and MR findings of intraventricular meningiomas are similar to those of extra axial meningiomas. Compared to extra-axial meningiomas, a greater proportion is calcified (50% compared to 20% for standard meningioma).The presence of brain invasion and metastasis is suggestive of non-benign intraventricular meningioma (5). The presence of huge intraventricular mass with heterogeneous signals on both T1 and T2 weighted MRI sequences, and heterogeneous enhancement pattern after gadolinium administration due to necrosis, should raise the suspicion of a non-benign meningioma (1). Benign intraventricular meningiomas, however, are more frequently iso-hypointense on T1, iso-hyperintense on T2 weighted images with intense and homogenous contrast enhancement(1). Non benign intraventricular meningiomas can spread quickly through the CSF to the subarachnoid space (3). Hence a neuraxis MRI is recommended in these patients (1).

 From a histopathological point of view, intraventricular meningiomas can arise from the velum interpositum, the tela choroidea and the choroid plexus stroma. Most of them are benign and the most frequent histological types are fibroblastic or meningoteliomatous, although other forms such as angiomatous, transitional or psammomatous have been reported. Among the malignant intraventricular meningiomas described , primary anaplastic forms predominate(1).

 Immunohistochemical test such as the Ki-67 labelling index (LI) is very important as it helps to differentiate atypical meningiomas from anaplastic types and may also help to predict the recurrence rate. The Ki-67 LI increases with the tumor grade significantly and supports the usefulness of Ki67 LI as a supplementary tool for grading(2).