Typical Meningiomas (WHO Grade I)

Definition: Mostly benign, slow-growing solid tumors arising from the arachnoid membranous layer of the meninges, which surrounds the brain and spinal cord.

Epidemiology: Most common primary brain tumor in adults, accounting for 36% of all brain tumors but comprise less than 3% of pediatric brain tumors. The vast majority occur as a solitary tumor (>90%) but can be multiple in the setting of prior radiation exposure or underlying syndrome such as neurofibromatosis type 2. Up to 70% of all meningiomas are benign, WHO grade I tumors, with grade II and grade III tumors accounting for 20%-25% and 1%-6%, respectively. Grades II and III tumors occur more frequently in men. Median age at diagnosis is 65 years, with higher incidence in women than in men with approximate ratio of 2.2:1. The incidence of meningioma is even higher in premenopausal women aged 35-44 years, where the ratio of women to men is 3.15:1. 2016 WHO central nervous system (CNS) Classification defines 15 different variants of meningioma based on histologic features:

Regardless of histologic features, meningiomas can be classified into at least 15 subtypes based on the anatomic location of tumor:

  • Cavernous sinus, suprasellar/tuberculum sellae, cerebellopontine angle, cerebral convexity, intraorbital, intraventricular, olfactory groove, parasagittal, falcine, tentorium, petrous ridge/face, posterior fossa, sphenoid, foramen magnum and spinal.

Affected age group: Although meningioma is the most common primary brain tumor in adults, it occurs very rarely in children with predilection for clear cell and rhabdoid subtypes.

Molecular and genetic profile: There are at least 15 different histologic subtypes of meningiomas (Table 2.1). Several molecular and genetic abnormalities have been detected (Table 2.1), with characteristic differences between WHO grade I and WHO grade II/III tumors: monosomy 22, deletion of 1p, losses of chromosomes 6q, 9p, 10, 14q, and 18q, NF2 gene → truncated and presumably nonfunctional merlin protein (a.k.a. schwannomin).

Cerebrospinal Fluid (CSF) markers: None

Clinical features and standard therapy: Symptoms of meningioma depend mainly on size, location, and growth rate of tumor. Meningiomas are usually slow growing, benign, and clinically indolent. For grade I meningiomas, gross total resection of tumor leads to cure although recurrence can be seen in rare cases. For grade II and III meningiomas, gross total resection does not necessarily ensure cure because they can recur both at the site of original tumor or at a distant site.

To minimize local recurrence, adjuvant radiation therapy is often used, especially when there is any residual tumor, but it does not prevent distant recurrence.


Meningiomas are circumscribed, dural-based masses that have similar density or signal to brain parenchyma on CT or MRI, respectively, and enhance avidly following the administration of intravenous contrast, both iodine-based and gadolinium-based intravenous contrast agents. Meningiomas often show “dural tail” enhancement, which is contiguous with the primary mass but extends farther into the adjacent dura. Most meningiomas are solid masses, but some can contain prominent cystic components. The imaging appearance of meningiomas can vary widely depending on the histologic subtypes and presence and degree of intratumoral calcium. Prominent intratumoral hemorrhage is rare in meningioma. Meningiomas can be cellular and show homogeneous reduced diffusion on diffusion-weighted imaging, and some are hypervascular, showing markedly increased vascularity on perfusion MRI.

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Jun 23, 2022 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Meningiomas

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