**4. Radiology**

Meningiomas present as well-defined extra-axial lesions with a typical peripheral CSF cleft. They present a homogeneous contrast enhancement on CT- and T1-weighted MRI with gadolinium administration. The tumor has a dural or bone implantation and a typical dural tail (contrast enhancement of the dura adjacent to meningioma implantation) (Figures 3 and 4). A reactive sclerosis of the underlying bone may be present in about half of skull-base meningiomas [17]. In rare cases, bone erosion is present (**Figure 5**). Calcifications or cystic portions may be present. Hyperintensity in T2-weighted MRI may denote a higher water content and thus an easily resectability during surgery.

**Figure 3.** T1-weighted coronal (a) and axial (b) MRI with gadolinium administration showing a well-defined extra-ax‐ ial lesion with an homogeneous enhancement and a contiguous dural enhancement (dural tail). A subtle CSF cleft is also visible between the lesion and the cerebral surface. These radiologic findings are typical for a convexitary menin‐ gioma.

**Figure 4.** A tentorial meningiomas with less demarcated limits and probably infiltrating the adjacent brainstem. The dural tail is evident in this T1-weighted MRI post gadolinium administration. This 33-year-old patient was irradiated during infancy after the resection of an ependymoma of the IVth ventricle. This may help in explaining the atypical features of the lesion.

**Figure 5.** This skull base meningioma completely eroded the skull base and encased the internal carotid artery on the left side. Also the vertebral artery was surrounded by the tumor (not shown). The anatomy was completely modified by the lesion, and a preoperative study of the images was essential to plan the surgery.

Meningiomas may present an associated venous invasion and MRI venography may help in evaluating sinus thrombosis in the preoperative period.

An angiography may be performed in the preoperative period to assess the vascularization of the lesion and the relationship with important vascular structures. Meningiomas are in most of cases vascularized by the meningeal artery supplying the meninges at the tumor sites, and the angiographic blush is also called mother-in-law blush, because it comes early and leaves late. However, because of the risks linked to this invasive procedure, it is often performed in the context of the planning of a preoperative embolization.
