Advanced imaging of feline brain meningioma

Meningioma is often a solitary mass broadly attached to the meninges. They are usually presented as a space-occupying mass lesion with isointense or slightly hypo- to hyperintense signals on T1-weighted (T1W) images and variably hypointense to hyperintense signals on T2-weighted (T2W) images on MRI. Meningiomas have marked and relatively homogeneous contrast enhancement and a dural tail sign is also typically observed. Due to these characteristic MRI findings, meningiomas are presumptively diagnosed by conventional sequences, but the definitive diagnosis is only made with histopathology.

Feline meningiomas tend to be very large masses and are typically located in the parietal lobe. Despites the large size the peritumoral oedema is not as big as expected or as compare to other more aggressive tumors. Transtentorial or cerebellar herniation and midline shift can be observed.

Hyperostosis of the calvarium is a particularity of feline meningiomas. A focal area of thickening of the bone adjacent to the region of meningeal enhancement can represent an area of hyperostosis in cats with meningiomas. This helps with the differential diagnosis and advise the surgeon for a titanium or PMMA reconstruction.

Sagittal T2WI image of a cat with a meningioma. The lesion is isointense to the brain parenchyma and producing brain and cerebellar herniation.

Transverse T2WI at the level of the piriform lobes from a cat with a large meningioma which is isointense to brain parenchyma.

On Computed tomography (CT) feline meninigomas can be easily recognized too. They are dural-base tumour that are typically iso attenuating to mild hyper attenuating. When contrast is given we tend to observed a homogenous and intense uptake of the iodinated contrast. Hyperostosis and intratumoral calcifications and/bleeding can also be observed if present.