|Clinical Overview: Meningioma
is the most common extraaxial brain tumor. They represent 20% of all
primary brain tumors. They are most common in adults and are usually
asymptomatic. They can arise in a radiation field many years after
As in this case, 5% are atypical and 1% are malignant, having a much worse prognosis.
|CT: They are sharply
circumscribed and lobulated mass that abuts the dura. The are extraaxial
thus forming an obtuse angle to the dura. This is a key observation in
making the diagnosis because they are the most common extraaxial brain
mass. Furethermore, the obtuse angle to the dura can be associated with a
"dural tail" sign which is highly suggestive of a meningioma
differentiating it from other extraaxial mass like a schwannoma (figure
1). On unenhanced CT, most of the time they are denser than brain. 20%
have calcifications. It enhances very brightly and occasionally have a
non-enhancing necrotic center. The amount of surrounding edema varies.
There is hyperostotic or osteolytic bony reaction in 20% of the cases. CT
can be 95% sensitive with contrast and 85% without contrast.
MRI: Finding are characteristic of extraaxial masses: 1. CSF/vascular cleft betweeen the mass and brain (figure 1) 2. displacement of gray-white matter interface around mass.
T1 - iso or slightly hypointense relative to cortex
Angio: Angiography demontrastes tumor blush that comes early and stays late which is has been called the "mother-in-law sign." Angiography is useful for preoperative embolization to decrease tumor vascularity. Also some cavernous hemangioma and capillary hemangiomas can look identical to a meningioma