Imaging in Brain Meningioma
- Author: German C Castillo, MD, FACR. FICS; Chief Editor: James G Smirniotopoulos, MD more...
Overview
Meningiomas represent 15% of all brain tumors. These lesions are the most common extra-axial tumors in the brain and the most frequently occurring tumors of mesodermal or meningeal origin.[1, 2, 3, 4, 5]
Advances in radiologic imaging techniques, such as computed tomography (CT) scanning and magnetic resonance imaging (MRI), have improved the surgeon's ability to predict the success for complete removal of the mass. Imaging information about the dural attachment site, location and severity of edema, and displacement of critical neurovascular structures is useful for planning the operative approach and affects outcome.[6, 7, 8] See the images below.
Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced computed tomography scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid, subtle edema, homogeneous enhancement, and ventricular dilatation are demonstrated. 
Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. The cystic cavity may be tumor necrosis, old hemorrhage, cystic degeneration, or trapped cerebrospinal fluid. Edema and midline shift to the left anterior aspect is observed. 
Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown. 
Brain meningioma. Parietal-convexity meningioma. Selective injection of the left middle meningeal artery shows inhomogeneous enhancing tumor. Intense vascularity is appreciated on the posterior aspect of the mass. Drainage veins are not seen. 
Brain meningioma. Nonenhanced T1-weighted sagittal magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone. 
Brain meningioma. Nonenhanced axial magnetic resonance image demonstrates a typical parasagittal meningioma. T1-weighted image shows a homogeneous, long-T1, round mass with thin capsule. The tumor is attached to the left side of the falx. Mass effect is noted on the adjacent gyri. Neuroradiologists and neurosurgeons must be aware of both the typical and atypical imaging appearances of meningiomas, as there is some correlation with different histologic types of tumor.
The World Health Organization (WHO) classifies meningiomas into 3 categories: (1) typical or benign (88-94%), (2) atypical (5-7%), and (3) anaplastic or malignant (1-2%). Significant factors contributing to recurrence include atypical and malignant histologic types (WHO classification) and heterogeneous tumor contrast enhancement on CT scans.
Anatomy
Meningiomas arise from arachnoid cells, particularly those packing the arachnoid villi, which protrude as fingerlike projections into the walls of the dural veins and sinuses. Most meningiomas grow inward toward the brain as discrete well-defined, dural-based masses and are spherical or lobulated. Flat tumors termed en plaque infiltrate the dura and grow as a thin carpet or sheet of tumor along the convexity dura, falx, or tentorium. Dural attachment of meningiomas can be pedunculated or broad-based (sessile). Because the pia and arachnoid form a membranous barrier between brain and tumor, some meningiomas grow into the subarachnoid space, but invasion of the brain is infrequent.
Preferred examination
MRI is preferred for the diagnosis and evaluation of brain meningiomas. CT scanning well depicts bony hyperostosis, which may be difficult to appreciate on MRI. CT scanning may, however, fail to demonstrate en plaque and posterior fossa meningiomas.
Limitations of techniques
CT scanning has limitations in performing direct imaging in any other plane than axial. However, with the onset of spiral CT scanning and, more recently, multisection or multidetector-row CT (MDCT) scanning, the quality of sagittal and coronal images that can be reconstructed from axial data has increased significantly. CT scanning is less helpful than MRI in differentiating different types of soft tissue.
Differential diagnosis and other problems to be considered
Brain astrocytoma, cavernous angiomas of the brain, neurofibromatosis type 2, central nervous system (CNS) sarcoidosis and CNS tuberculosis are included in the differential diagnosis. Other conditions to consider are dural vascular malformation, hemangioma, and extramedullary hematopoiesis.
Radiologic intervention
The development of catheters and the continued refinement of embolic materials and radiographically controlled interventional procedures have contributed to improved treatment of patients with brain meningiomas. The clinician must be aware of the active participation of the neurosurgeon and neuroradiologist in the therapy of neurosurgical patients.[9, 10]
The best available treatment for benign meningiomas is complete surgical resection of the tumor. Nevertheless, interventional neuroradiologists should contribute in performing preoperative embolization to reduce the blood supply to the tumor. All meningiomas are benefited by embolization, but especially those with a complex presentation, giant meningiomas, meningiomas exhibiting malignant or angioblastic characteristics, or meningiomas involving the skull base, scalp, or critical vascular structures.The preoperative embolization of meningiomas is commonly used to facilitate surgery.
Embolization can be carried out at the same time as the diagnostic angiography session or may occur later if detailed procedural planning is required. Distal, homogeneous, and permanent occlusion of the vascular bed by injecting small particles (150-300 microns of polyvinyl alcohol [PVA]) through microcatheters is the goal. Bilateral dural devascularization shortens the surgical resection time and permits total removal of the tumor. The procedure causes tumor necrosis, expanding the spectrum of meningiomas that can be safely resectioned during surgery.
PVA particles ranging in size from 100 to 2000 microns have been used, but the newer class of deformable particles and Bead Block have been shown to be more effective in distal embolotherapy to reach the capillary bed of the meningioma. Embospheres can be tagged with chemotherapeutic agents. Several meningiomas of the convexity have been embolized with Embospheres in our experience.
Approximately 2% of patients have complications associated with embolization that result in neurologic deficits. At the theoretical level, embolization may reduce the likelihood of recurrence. Embolization also may be the only treatment required in older or high-risk patients. See the images below.
Brain meningioma. Cerebellopontine angle meningioma. T2-weighted magnetic resonance image shows a hyperintense mass attached to the petrous bone. Sharply defined tumor margin, subtle edema, and mass effect on the fourth ventricle and the brainstem are present. Hyperintensity on the T2-weighted image indicates a soft tumor consistency and microhypervascularity, which is seen more often in aggressive, angioblastic, or meningothelial meningioma. 
Brain meningioma. Cerebellopontine angle meningioma. Selective angiogram of right occipital artery shows focal hypervascularity through the auricular artery. Early and delayed staining is seen. 
Brain meningioma. Cerebellopontine angle meningioma. Right occipital artery embolized with polyvinyl alcohol particles before surgery. 
Multiple meningiomas. A: Sagittal T1-weighted magnetic resonance image (MRI) demonstrates posterior fossa and parietal meningiomas. B: Gadolinium enhancement on sagittal T1-weighted MRI shows intense enhancing of the masses. C: T2-weighted coronal MRI shows stable hypointense appearance of the posterior mass after endovascular embolization. 
Malignant and multiple meningiomas. A 47-year-old white male underwent gamma knife surgery due to left convexity meningioma, followed by microsurgical removal of the tumor in 2001. A, B: Four years later, in 2005, MRI showed a stable residual parietal/occipital mass. The left sigmoid sinus is occluded. C, D: One small right frontal meningioma also underwent radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated. 
A-D: Coronal T2-weighted and enhanced T1-weighted magnetic resonance images demonstrate quick growth of a convexity mass toward the tentorium and the petrous bone. This bone structure is filled with liquid in its inferior aspect. Surgical biopsy reported "atypical meningioma." 
Coronal computed tomography scan. This bone window shows petrous bone destruction and partial lack of bone plane after surgical removal of the tumor. 
Digital subtraction angiography. A, B: Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C: Occipital artery. D: The branches were embolized before the surgical procedure. The tumor was partially removed due to cranial base involvement. 
Frontal meningioma. A, B: Slow growth and surrounding edema is seen on magnetic resonance imaging (MRI) control of this tumor. Coronal, enhanced-T1 weighted and fluid attenuation inversion recovery (FLAIR) sequences are shown. C, D: Digital angiography. Right media meningeal branch demonstrates feeding of the tumor. It was not embolized. 
A: 3-dimensional (3-D)-enhanced T1-weighted magnetic resonance image (MRI) image shows residual meningioma at the cranial base after second surgical removal. B: Coronal T2-weighted MRI shows intense edema surrounding the frontal mass. C: 3-D image on enhanced T1-weighted MRI demonstrates frontal meningioma underlying the orbital right sulcus. D: Gadolinium-enhanced, axial T1-weighted image shows 1 of the 3 focal hyperintense masses discovered only on this sequence. Brain metastases from meningioma have not been proved. Special concerns
A growing number of lawsuits that name radiologists involve special procedures.[11, 12, 13, 14] Good technique, good planning, and informed consent, which includes the involvement of the interventional neuroradiologist, can help physicians prevent most claims.
Radiography
In most patients, no findings of meningiomas are present on plain radiographic examination. Plain skull images may demonstrate calcification in meningiomas of the skull base or convexity. Meningiomas displayed reactive hyperostosis without connection to the size of the tumor. Rare osteolysis is associated with the benign and aggressive meningiomas.
Degree of confidence
Most plain skull radiographs do not depict signs of meningiomas. Meningiomas en plaque have diffuse hyperostosis, more frequently observed over the sphenoid wing and pterion. This finding results in a high degree of confidence.
False positives/negatives
Calcification within the tumor is a considerably less frequent plain radiographic manifestation; therefore, false-negative results occur. Most patients with brain meningiomas do not undergo radiographic imaging because the diagnosis has been made directly with CT scanning or MRI.
Computed Tomography
CT scanning has several advantages in the imaging of meningiomas.[15, 16, 17, 18, 19, 20, 21, 22] Invasion of surrounding dura frequently provokes an osteoblastic response, causing hyperostosis.[23] This imaging modality is used best for demonstrating calcification of meningiomas (see the images below). The CT nature of the calcification may be nodular, fine and punctate, or dense.
Brain meningioma. Nonenhanced computed tomography scan demonstrates a middle fossa meningioma. The calcified mass is attached to the anterior ridge of the right petrous bone. Ring and punctate calcification are depicted. Edema is not appreciated. 
Two different cases. A, B: Computed tomography (CT) scans depict calcified meningiomas from the parietal convexity. C: Nonenhanced axial CT image shows homogeneous calcified mass attached to the right parietal bone. Soft-tissue tumor is seen at the posterior aspect of the calcification (large arrow). Other minor calcifications on the left cerebral hemisphere are caused by a parasitic disease. D: Coronal T2-weighted magnetic resonance image demonstrates calcium deposit (star) surrounded by solid tissue (small arrow); edema is not seen in this case. CT scanning is effective in showing hyperostosis, bone destruction, and erosion at the site of the dural attachment (see the following images). Hyperostosis is seen in 15-20% of patients.
Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. The cystic cavity may be tumor necrosis, old hemorrhage, cystic degeneration, or trapped cerebrospinal fluid. Edema and midline shift to the left anterior aspect is observed. Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown. 
Brain meningioma. Malignant frontal-convexity meningioma. Computed tomography scan of the frontal internal table and diploe shows erosion and bone infiltration. CT scanning can also show acute tumor hemorrhage and widened vascular grooves in the calvarium. In addition, homogeneous masses with attenuation similar to the surrounding brain make up 25-33% of meningiomas. The remainder are hyperattenuating compared with the brain. Meningiomas can exhibit extensive edema. Inhomogeneous enhancement can result due necrosis or rare hemorrhage. Edema is absent in 50% of patients because of slow growth, but it may be extensive. Edema predominantly affects white matter, and it resembles fingers of low attenuation units. See the images below.
Brain meningioma. Nonenhanced computed tomography scan shows an isoattenuating sphenoid-wing meningioma. The left sylvian fissure is partially collapsed. 
Brain meningioma. Computed tomography scan shows an isoattenuating sphenoid-wing meningioma. The contrast-enhancing mass is attached to the major sphenoid wing and was demonstrated only after the intravenous injection of contrast material. Contrast-enhanced CT scanning displays moderate to strong homogeneous enhancement in most tumors. Steinhoff et al observed a nodular blush in 97%, a mixed inhomogeneous blush in 0.5%, and a ring blush in 1.5%.[24] In a study by Naidich et al, tumor blush was nodular and nearly homogeneous in 70% of patients, inhomogeneous in 24% of patients, and ringlike in 2% of patients.[25]
Cystic components of the meningiomas may be present inside the tumor or between the tumor and the adjacent brain, so-called trapped CSF. Peripheral cysts resulting from trapped CSF can also be present. See the image below.
Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced computed tomography scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid, subtle edema, homogeneous enhancement, and ventricular dilatation are demonstrated. Degree of confidence
Meningiomas are well-circumscribed peripheral or falcine masses that deform the brain. About 90% of meningiomas are demonstrated on CT scans. The main role of CT scanning, as opposed to other imaging modalities, is the demonstration of adjacent bone changes and calcification within the lesion.
Atypical CT scan features are the primary reason for preoperative misdiagnosis. Posterior fossa meningiomas may be missed by this imaging modality, as will be some en plaque lesions. CT scanning can fail to demonstrate cystic changes in intracranial meningiomas. CT scan features, such as irregular areas of nonenhancing mass and well-defined regions of persistent low attenuation, are the reason for preoperative misdiagnosis.
False positives/negatives
False-negative findings can occur with cystic changes in brain meningiomas; false-positive findings can occur with large dural calcification, which can mimic the disease.
Magnetic Resonance Imaging
An important advantage of MRI in the imaging of meningiomas is its superior resolution of different types of soft tissue, multiplanar capability, and 3-dimensional (3-D) reconstruction (see the images below).[17, 18]
Parasagittal meningioma. A: Nonenhanced Sagittal T1-weighted magnetic resonance image (MRI) shows a solid dural isointense mass with bone invasion and compression against the parietal cortex. B: Contrast-enhanced sagittal T1-weighted MRI demonstrates partially intense enhancement of the tumor. C: Coronal T2-weighted image shows isointense mass meaning hard tissue. This finding is observed on fibroblastic meningiomas. D: Contrast-enhanced T1-weighted axial MRI shows hyperintense image located within the bony marrow. 
A: Noncontrast angio-magnetic resonance image (MRI) on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B: MRI reconstruction shows sagittal venous obstruction and 3-dimensional (3-D) appearance of the tumor. MRI can demonstrate tumor vascularity, arterial encasement, venous sinus invasion, and the relationship between the tumor and surrounding structures. This modality is particularly advantageous in depicting the juxtasellar area and the posterior fossa and in demonstrating the rare presence of disseminated disease via the CSF. The multiplanar capability is often the best means to visualize the broad contact of tumors to the meninges, tumor capsules, and meningeal contrast enhancement adjacent to the tumor.[26, 27, 28] See the following images.
Brain meningioma. Nonenhanced T1-weighted sagittal magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone. Brain meningioma. Nonenhanced axial magnetic resonance image demonstrates a typical parasagittal meningioma. T1-weighted image shows a homogeneous, long-T1, round mass with thin capsule. The tumor is attached to the left side of the falx. Mass effect is noted on the adjacent gyri. 
Brain meningioma. Coronal T2-weighted magnetic resonance image demonstrates a typical parasagittal meningioma. Isointense and inhomogeneous tumor without peripheral edema indicates a more fibrous and harder character (ie, a fibroblastic meningioma). 
Brain meningioma. Contrast-enhanced T1-weighted axial magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, enhancing, globose mass is depicted. 
Brain meningioma. Contrast-enhanced T1-weighted coronal magnetic resonance image shows a typical parasagittal meningioma. A homogeneous, enhancing, globose mass is depicted. On nonenhanced T1-weighted images, most meningiomas have no signal intensity difference compared with cortical gray matter. Fibromatous meningiomas may be more hypointense than the cerebral cortex. Meningiomas are hyperintense on T2-weighted images, and T2-weighted images also show the extent of edema. See the images below.
Multiple meningiomas. A: Sagittal T1-weighted magnetic resonance image (MRI) demonstrates posterior fossa and parietal meningiomas. B: Gadolinium enhancement on sagittal T1-weighted MRI shows intense enhancing of the masses. C: T2-weighted coronal MRI shows stable hypointense appearance of the posterior mass after endovascular embolization. Malignant and multiple meningiomas. A 47-year-old white male underwent gamma knife surgery due to left convexity meningioma, followed by microsurgical removal of the tumor in 2001. A, B: Four years later, in 2005, MRI showed a stable residual parietal/occipital mass. The left sigmoid sinus is occluded. C, D: One small right frontal meningioma also underwent radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated. On MRI and CT, meningiomas exhibit the same enhancement appearance after the injection of contrast medium. Intense enhancement is seen in 85% of tumors. A ring appearance may represent a capsule.
Meningiomas have a collar of thickened, enhancing tissue that surrounds their dural attachment; this is also known as a dural tail. This sign represents thickened dura, which may be either reactive or neoplastic. A dural tail occurs in approximately 65% of meningiomas and 15% of other peripheral tumors; therefore, it is a good predictor of lesion identity. Although this radiographic feature is not specific for meningiomas, it is highly suggestive of the diagnosis.
Histologic subtypes may have different MRI appearances, but this does not suffice for a histologic diagnosis by using MRI.
Hyperintensity on T2-weighted images indicates soft-tumor consistency and microhypervascularity. This is seen more often in aggressive, angioblastic, or meningothelial tumors. T2-weighted signal intensity is best correlated with both the histology and consistency of the meningioma. Generally, low-intensity portions of the tumor on T2-weighted images indicate a more fibrous and harder character (eg, fibroblastic meningiomas), whereas higher-intensity portions indicate a softer character (eg, angioblastic tumor).[29, 30, 31]
A typical meningioma is a homogeneous, markedly enhancing extra-axial mass. It may show meningeal cysts, ring enhancement, fatty transformation, and en plaque morphology. Malignant meningiomas may invade the calvarium and cerebral parenchyma (1%).
Most meningiomas can be diagnosed by MRI.[17, 18, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41] MRS reveals lactate in embolized areas of the meningioma immediately after embolization. Lipids are not observed before the third day after embolization and are always associated with avascular and soft tissue at the time of surgery.
Gadolinium warning
Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.
NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
Degree of confidence
In general, the sensitivity and specificity of MRI are high in the diagnosis of meningiomas. MRI has proved to be superior in delineation of the tumor and its relation with surrounding structures. However, MRI is unreliable for recognition of tumor calcification, and acute hemorrhage is often difficult to image with this modality.
False positives/negatives
False-negative findings of tumor calcium must be considered. Delineation of acute hemorrhage into tumor with conventional sequences is a disadvantage of MRI and may generate false findings.
Ultrasonography
The location of intratumoral hemorrhage, cystic changes inside or outside of the tumor mass, calcifications, invasion of the parenchyma by malignant meningiomas, and lobulated or multilobulated masses is demonstrable only with intraoperative ultrasonography.
Angiography
Although magnetic resonance angiography (MRA and magnetic resonance venography [MRV]) have decreased the role of classical angiography, the latter remains a powerful tool for embolization and planning surgery. Angiography is still indispensable if embolization of the tumor is deemed necessary (see the image below).[39, 42, 43]
A: Noncontrast angio-magnetic resonance image (MRI) on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B: MRI reconstruction shows sagittal venous obstruction and 3-dimensional (3-D) appearance of the tumor. Meningiomas are supplied by meningeal branches of the internal and external carotid artery (see the following images). Basal meningiomas of the anterior and middle cranial fossa and meningiomas of the wings of the sphenoid bone are commonly supplied by the internal carotid artery. Other supratentorial meningiomas are supplied by the internal and external carotid arteries.
Brain meningioma. Middle fossa meningioma. Internal carotid artery demonstrates considerable supply from petrous branch. The external carotid artery provided the main blood supply to the tumor. 
Brain meningioma. Parasellar meningioma. Lateral projection from internal carotid angiography shows multiple opacified tumoral vessels in a radial distribution. Circumferential narrowing of the supraclinoid carotid portion is depicted. Tumors that arise along the falx, the sphenoidal ridge, and the convexity are supplied by the middle meningeal artery. Falcine meningiomas can be supplied additionally by the anterior meningeal artery. Parasellar and tentorium tumors are supplied by the hypophyseal meningeal artery. Direct meningeal arteries from the cavernous sinus can supply meningiomas of the middle cranial fossa. Intraventricular tumors are supplied by anterior and posterior choroidal arteries. See the images below.
Brain meningioma. Parietal-convexity meningioma. Selective injection of the left middle meningeal artery shows inhomogeneous enhancing tumor. Intense vascularity is appreciated on the posterior aspect of the mass. Drainage veins are not seen. External carotid and vertebral branches supply tumors of the posterior fossa. Large meningiomas can be supplied by pia vessels around the tumor.
Meningeal arteries penetrate to a meningioma through its dural attachment with inside branches radially distributed like sunrays. Homogeneous sharp tumor staining is seen early and remains late. Usually, meningiomas do not exhibit drainage veins, but angioblastic types can display it.
In summary, angiography is useful in delineating the blood supply of the external versus internal carotid arteries and can show encasement of intracranial vessels. Angiography demonstrates an arterial map for preoperative embolization (see the image below).
Brain meningioma. Cerebellopontine angle meningioma. Selective angiogram of right occipital artery shows focal hypervascularity through the auricular artery. Early and delayed staining is seen. Brain meningioma. Cerebellopontine angle meningioma. Right occipital artery embolized with polyvinyl alcohol particles before surgery. Digital subtraction angiography. A, B: Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C: Occipital artery. D: The branches were embolized before the surgical procedure. The tumor was partially removed due to cranial base involvement. 
Embolization may be the only treatment required in older or high-risk patients. Meningeal vessels from the internal carotid artery should supply the tumor. Mass effect should persist after embolization of the middle meningeal artery. As an alternative to traditional catheter angiography, 3-D CT angiography may depict the relationship between skull base meningiomas and neighboring bony and vascular structures clearly, quickly, and with minimal risk to the patient.
Degree of confidence
Angiography has a high degree of confidence in recognizing the arterial source of the meningioma. Tumor feeding can be identified with a low rate of false-positive and/or false-negative findings.
False positives/negatives
Arterial findings have a high sensitivity and specificity in the diagnosis of meningiomas. Angiography shows an arterial map for preoperative embolization with a low false-finding rate.
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