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With this knowledge, neurosurgical gross-total resection still represents the gold standard for patients’
treatment, with radiotherapy used as adjuvant treatment in the case of non-radically removed lesions
(whereas external-beam radiation was not demonstrated to be associated to better results compared
[6,7]
to surgery followed by adjuvant radiation) . Surgical planning largely relies on MRI and CT scans
examination, as the type of surgery performed can vary depending on tumor size and location. Different
surgical techniques have been used for meningiomas. The most common approach is represented by
craniotomy, in which brain exposure ensures tumor visualization on the brain surface, minimizing the risk
of damaging adjacent structures. Another possible alternative is represented by neuroendoscopy-assisted
microscopic resection techniques. Neuroendoscopic surgery is largely used for meningiomas within
the ventricular chambers, whereas for ventral skull base meningiomas a possible option is represented
by endoscopic endonasal surgery; however, while for olfactory groove or tuberculum sellae this latter
approach has been widely validated, its use remains controversial in other skull base regions (such as
cavernous sinus, petro-clival, or cranio-facial regions). Moreover, since meningiomas obtain vascular
supply from extracranial and intracranial circulation, preoperative embolization can be used in selected
cases as adjuvant therapy to reduce intraoperative bleeding and make surgery more effective; specific
imaging techniques (such as perfusion and angiography) can provide information on meningioma’s
perfusion status, amenability to embolization based on blood supply, and eventual anatomical references
that could help in the delivery of embolic materials. After partial resection, the disease-free survival rates
range between about 60% at five years and 10% at 15 years, with ever-increasing tendency to recurrence
over time. Nevertheless, also in the case of complete surgical removal, the overall rate of meningioma
[8,9]
recurrence remains not negligible, as it is estimated to range 15%-25% at 20 years .

With this background, it can be easily understood why neuroimaging plays a crucial role not only in
meningioma first diagnosis, but also in therapeutic planning and long-term surveillance (for early detection
of both recurrence in treated patients and disease progression in untreated ones). Here, we review the
conventional findings in meningioma imaging, discuss the role of advanced diagnostic techniques, and
offer an overview on possible future neuroimaging applications for lesions’ characterization.

CONVENTIONAL IMAGING
Intracranial meningiomas
Intracranial meningiomas typically show characteristic neuroimaging features well detected on both CT
and MRI studies, which allow the correct diagnosis with high diagnostic accuracy. MRI is the gold standard
technique for meningiomas detection and evaluation because it provides soft tissue characterization,
[10]
high contrast definition and possibility of multiplanar reconstructions . Meningiomas appear as extra-
axial dural-based masses, with the exception of en plaque meningioma, exhibiting sheet-like appearance
[11]
due to its extensive dural extrinsecation . On conventional MRI, they usually are hypo- to isointense on
T1-weighted sequences, with variable signal on T2-weighted sequences due to the presence of necrotic
cystic or calcific areas; most of them are avidly and homogeneously enhancing after paramagnetic agents
administration [Figure 2] [12,13] . T2w images also allow for crescent-shaped cerebral-spinal fluid (CSF) cleft
between tumor and brain parenchyma identification, while post-contrast sequences allow for the detection
of the characteristic dural tail, due to adjacent dural reactive changes . Edema in surrounding brain
[14]
tissue is evident in about half of cases, generally due to the presence of atypical features related to a more
[15]
aggressive biological behavior rather than to overall dimension ; on diffusion-weighted images (DWI),
brain edema is typically vasogenic, due to different mechanisms such as venous obstruction, pial vessel
paralysis, and vessel barrier alteration [16-19] . DWI has also been used to depict higher-grade meningiomas
with increased cellularity, which show reduced values on corresponding apparent diffusion coefficient
(ADC) maps [20-22] ; however, it should be noted that the correlation between DWI and tumor grade remains
controversial, as no univocal statistical correlation between ADC values and tumoral behavior has been
established yet . Other imaging characteristic that have been proposed as indicative of a more aggressive
[23]