eMedicine Specialties > Radiology > Brain/Spine

Meningioma, Brain

German C Castillo, MD, FACR. FICS, Assistant Professor, Department of Diagnostic and Interventional Radiology, Harvard Clinic and Central University of Ecuador

Updated: Mar 10, 2010

Introduction

Background

Meningiomas represent 15% of all brain tumors. They are the most common extra-axial tumors in the brain and the most frequently occurring tumors of mesodermal or meningeal origin.

Advances in radiologic imaging techniques, such as CT and 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 does affect outcome. See the images below.

Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced CT scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid (arrows), subtle edema, homogeneous enhancement, and ventricular dilation are demonstrated.

Brain meningioma. Nonenhanced CT scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown.

Brain meningioma. Nonenhanced CT scans shows an isoattenuating sphenoid-wing meningioma. The left sylvian fissure is partially collapsed.

Brain meningioma. Nonenhanced T1-weighted sagittal MRI demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule (arrow) is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone.

Brain meningioma. Nonenhanced axial MRI 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. Contrast-enhanced T1-weighted axial MRI demonstrates a typical parasagittal meningioma demonstrated. A homogeneous, enhancing, globose mass is depicted.

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.

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Brain Cancer.

Recent studies

Pfisterer et al studied 68 resected tissue samples of meningiomas using ex vivo (1)H-MRS to differentiate meningioma grade. The absolute concentrations of total alanine and creatine were found to be decreased in high-grade meningiomas, as was the ratio of glycine to alanine. Also, alanine and the glycine/alanine ratio distinguished between primary and recurrent meningiomas; and the absolute concentrations of alanine and creatine and the glycine/alanine and choline/glutamate ratios were associated with rapid recurrence. According to the authors, these data indicate that meningioma tissue can be characterized by metabolic parameters that are not typically identified by histopathologic analysis alone. Creatine, glycine, and alanine may be used as markers of meningioma grade, recurrence, and the likelihood of rapid recurrence.^{[1 ]}

Righi et al studied 36 biopsies of patients with brain tumors that included glioblastoma multiforme (GBM); low-grade (LG), including schwannoma and pylocytic astrocytoma; meningioma (MN); and brain metastases (MT) to test whether glycine measurements may help distinguish between these various tumors, using high-resolution magic angle spinning (HRMAS) (1)H-MRS. Higher levels of Gly were found in all tumor biopsies compared with controls. Gly levels were also found to be significantly elevated in LG, MT, and GBM biopsies; and levels were higher in GBM than LG. Gly levels in GBM and MT did not differ significantly, but the Gly:Myo (myo-inositol) ratio did distinguish GBM from MT and from all other groups. Residual Myo levels were elevated in LG and MT and reduced in MN and GBM. The authors concluded that Gly can serve as a biomarker for brain tumors and that the Gly:Myo ratio may be a useful index for brain tumor classification.^{[2 ]}

Chernov et al used (1)H-MRS for metabolic characterization of the peritumoral brain in the vicinity of meningiomas. Analyzed metabolites included N -acetylaspartate, choline-containing compounds, mobile lipids, and lactate. The most prominent (1)H-MRS-detected brain abnormality in the vicinity of intracranial meningiomas was a significant decrease of N -acetylaspartate content,. The investigators concluded that peritumoral spectroscopic alterations may be predictive of invasive tumor growth and may correspond to presenting neurologic symptoms.^{[3 ]}

Rosenberg et al evaluated the outcomes of 13 patients (24 surgeries) with grade III meningiomas, as defined by the 2007 World Health Organization standards. The 24 surgeries consisted of 13 primary, 7 salvage, and 4 second salvage. In addition, patients received a total of 14 courses of radiotherapy (RT), including fractionated RT in 3 patients following primary surgery; fractionated RT in 4 patients following salvage surgery; salvage stereotactic radiosurgery to 6 areas in 3 patients; and salvage intensity-modulated RT in 1 patient. Following primary surgery, median survival was 3.4 years; 5-year survival rate was 47.2%; and 8-year survival rate was 12.2%. Median time to recurrence was 9.6 months. Patients who received adjuvant RT after initial surgery, as compared with surgery alone, tended toward longer survival. Radiation necrosis developed in 2 patients, and surgical complications occurred in 3 patients.^{[4 ]}

Pathophysiology

Meningiomas are believed to arise from the same cells that give rise to the arachnoid villi and arachnoid endothelium. Surface meningiomas originate from the arachnoid cells embedded in the dura, while intraventricular tumors arise from pia-arachnoid rests. Meningiomas occur more frequently where the villi usually are most numerous, such as along the major dural venous sinus. The tumors typically have a definite dural attachment.^{[5 ]}

Frequency

United States

In males, the prevalence of meningiomas is 1.2 cases per 100,000 population. In females, the prevalence is 2.6 cases per 100,000 population. The ratio of meningiomas to gliomas in a Mayo Clinic group was 1:2. Relative frequency of intracranial tumors in large series by Zimmerman attributed 12.5% of tumors to meningiomas.^{[6 ]}

International

Meningiomas constitute 30% of brain tumors in Bantus, Africa. European reports show meningiomas account for approximately 15% of brain tumors.

It has been reported that the incidence of meningioma increased in several industrialized countries in the late 1970s and early 1980s. In Denmark, Finland, Norway and Sweden the combined incidence among men increased from 1.4 to 1.9 per 100,000 during the follow-up period; the corresponding rates for women were 2.6 and 4.5. The decrease in the rate or detection postmortem has affected the incidence time trend, but it also coincides with widespread use of new imaging technologies. The high incidence of meningiomas in Iran (29%) is thought to be partly due to the late effect of mild doses of radiation of the scalp that some of these patients received in early childhood for treatment of ringworm of the scalp.

No overall increased risk of glioma or meningioma has been observed among cellular phone users; however, for long-term cellular phone users, results need to be confirmed before firm conclusions can be drawn.

Mortality/Morbidity

Survival rates from surgical series are 82%, 72%, and 60% at 2, 5, and 10 years, respectively.

• At 5 years, no difference is noted in survival rates for males versus females or for race or ethnicity.
• Among patients older than 70 years who underwent surgery for meningioma, the neurologic complications rate reached approximately 23% and was approximately 3% in younger patients.
• In general, postoperative results are better in patients with few concomitant diseases, smaller meningiomas, less edema, shorter surgery times, and a more accessible location (ie, convexity rather than skull base).

Race

During 1975-1985, ethnic analysis from the Armed Forces Institute of Pathology, Washington, DC, showed a slightly higher frequency of meningiomas in blacks, with a white-to-black case ratio of 6.7:1, as compared with the US white-to-black population ratio of 7.4:1. More meningiomas are found in African Americans than in other Americans.^{[7 ]}

The following findings strongly suggest that meningioma is one of the tumors induced by atomic bombing in Hiroshima. Sixty-eight patients surgically treated for meningioma who had been within 2.0 km of the hypocenter of the explosion were identified. Six hundred and seven non-exposed patients with meningioma were also studied. Treatment dates were from 1975 to 1992. The incidences of meningioma among the survivors of Hiroshima in 5-year intervals since 1975 were 5.3, 7.4, 10.1, and 14.9, respectively. The incidences of meningioma classified by distances from the hypocenter of 1.5-2.0 km, 1.0-1.5 km and less than 1.0 km were 6.3, 7.6 and 20.0, respectively.

Sex

Meningiomas are more common in women than in men, with a male-to-female ratio of 1:2. A reverse male-to-female preponderance of 3:1 has been reported in the malignant form. In a statistical survey of sphenoid ridge meningiomas, 97% were found in female patients.

An increased relative risk of meningioma has been found among postmenopausal women for ever use of hormone replacement therapy, with an odds ratio of 1.7 (95% confidence interval: 1.0, 2.8). Women who had used long-acting hormonal contraceptives (subdermal implants, injections, or hormonal intrauterine devices) had an increased risk of meningioma; the odds ratio for at least 10 years of use was 2.768% of hospital consultant episodes for benign neoplasm of meninges were for women in England 2002 (Hospital Episode Statistics, Department of Health, England, 2002-03).

Age

Meningiomas have a predilection to occur from the third to sixth decades of life, with a peak incidence occurring in individuals aged approximately 45 years.

• Meningiomas are rare in patients younger than 20 years, and if present, commonly are associated with neurofibromatosis type 2. Of all intracranial meningiomas, 1-2% occur in children and adolescents.
• Intraventricular meningiomas represent 2% of intracranial meningiomas in the adult population but 15-20% of intracranial meningiomas in the pediatric population.
• Tumor genesis of meningioma has been associated with chromosome 22, most notably the NF2 gene, but additional genes have been implicated in meningioma development. It has been reported the identification of five novel immunogenic antigens expressed in meningiomas.Only seven cases of meningioma associated with Gorlin's syndrome have been described. This syndrome, also known as multiple basal cell carcinoma syndrome, is a familial tumor condition with autosomal-dominant inheritance. 40 cases have been described. Patients develop multiple basal cell carcinomas beginning in childhood.61 was the mean age of patients hospitalized for benign neoplasm of meninges in England 2002-03 (Hospital Episode Statistics, Department of Health, England, 2002-03)

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. Most of them 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). Since 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.

Grossly, meningiomas usually show a lamellar internal structure with a firm central core at the dural attachment and a surrounding, softer, vascular mass at the periphery. The tumor may have a fibrous, soft, or psammomatous-calcified texture and be grossly irregular, reddish, and vascularized. About 90% of meningiomas are located in the supratentorial compartment. Frequent locations are along the falx and laterally over the cerebral convexity. The sphenoidal ridge, juxtasellar area, olfactory groove, posterior fossa, and tentorium are other important sites of attachment. Almost all intraventricular tumors are located in the third or fourth ventricles and the trigone of the lateral ventricle, arising from the velum interpositum or tela choroidea. Occasionally, they arise inside of the frontal horn, near the foramen of Monro, with a slight left-sided predilection (see Table).

Rare examples of meningiomas within the cerebral hemispheres, with no dural attachment, are derived from stromal cells in the spaces surrounding the perforating blood vessels. These are extremely rare.

Microscopically, appearance is variable. The histologic variants include meningotheliomatous, fibroblastic, transitional, psammomatous, angioblastic, and malignant tissue. 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%).

Presentation

Except when they compress critical areas, meningiomas can remain clinically asymptomatic for years because of their slow growth. Meningiomas can reach a large size, especially in the frontal lobes, with few symptoms. The primary complaints of patients include focal deficit, seizures, psycho-organic syndrome, and headaches. Usually, the mean duration of symptoms is approximately 15 months, with 30% of histories lasting less than 3 months. Obstruction of CSF pathways is not common because of the convex attachment of tumors, with the exception of intraventricular and posterior fossa locations. Symptoms resulting from tumor hemorrhage are infrequent. Origins of surgically verified meningiomas

The clinical behavior of the syncytial, transitional, and fibroblastic histologic types is identical. Angioblastic tumors are more aggressive and have a greater tendency to recur. Anaplastic (sarcomatous) tumors may metastasize to lung, abdominal viscera, and bones. Although the vast majority of meningiomas are benign, a rare malignant form exists; this is termed malignant meningiomatosis or sarcomatosis.

Metastases from malignant meningioma involve the vertebral bodies, liver, pelvis, long bones and the spinal cord. It has been reported to be less than 1 per 1,000. This confers an incidence of metastasis of 0.76% when considering all the meningiomas, and an incidence of approximately 43% when considering only malignant meningioma.

Significant factors contributing to recurrence include the following:

• Incomplete surgical resection (Simpson classification)
• Atypical and malignant histologic types (WHO classification)
• Presence of nucleolar prominence
• Presence of more than 2 mitoses per 10 high-power fields
• Heterogenous tumor contrast enhancement on CT scan

Patients without any of these features showed low recurrence rates of 4% and 18% at 5 and 10 years, respectively.

In the past, microsurgery was the goal of total tumor removal. A more complete removal is associated with a lower risk of recurrence or progression. The surgical removal usually includes bone and/or into which the tumor has spread.

With the increasing availability of radiosurgery throughout the U.S. and the world, surgeons have had to rethink radical surgical removal for tumors that recur or are unresectable. Gamma knife (GK) is mainly used for small (<3 cm in diameter) residual, recurrent, or tentorial meningiomas. The relatively low minimum tumor radiation dose for skull base meningiomas results in low morbidity. Radiosurgery now is able to provide palliative treatment with favorable long-term tumor outcomes and low morbidity.

Complete resection is the optimal treatment for atypical meningiomas, taking into account the tumor site and feasibility. For small- and medium-sized atypical meningiomas, the gamma knife may be a safe adjunct to other treatment modalities.

Radiosurgery has proved to be effective in improving meningioma-related trigeminal pain. GK for intracranial meningiomas seems to be a safe and effective treatment. However, meningiomas of the convexity, parasagittal region, or falx cerebri have a higher incidence of peritumorous imaging changes after GK than those of the skull base.

The anti-progestational drug mifepristone (RU 486), lovastatin as a potent inhibitor of meningioma cell proliferation, and hydroxyurea chemotherapy have been suggested as causing regression of unresectable and recurrent meningiomas. Surgical removal of the tumor, radiation therapy, radiosurgery, and/or growth-modifying drugs may contribute to the best outcome.

Preferred Examination

MRI is preferred for diagnosis and evaluation. CT well depicts bony hyperostosis, which may be difficult to appreciate on MRI. CT may, however, fail to demonstrate en plaque and posterior fossa meningiomas.

Limitations of Techniques

CT 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 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 Diagnoses

Astrocytoma, Brain
Brain, Cavernous Angiomas
Neurofibromatosis Type 2
Sarcoid, CNS
Tuberculosis, CNS

Other Problems to Be Considered

Dural vascular malformation
Hemangioma
Extramedullary hematopoiesis

Radiography

Findings

In most patients, no findings 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. 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 by using CT or MRI.

Computed Tomography

Findings

CT scanning has several advantages in the imaging of meningiomas. Invasion of surrounding dura frequently provokes an osteoblastic response, causing hyperostosis.^{[8 ]}

CT is the imaging modality 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. Histologic studies have demonstrated calcification in up 45% of meningiomas.

Brain meningioma. Nonenhanced CT scans 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. CT scans depict calcified meningiomas from the parietal convexity. C, D. 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. Coronal T2 weighted MRI demonstrates calcium deposit (star) surrounded of solid tissue (small arrow); edema is not seen in this case.

CT is effective in showing hyperostosis, bone destruction, and erosion at the site of the dural attachment. Hyperostosis is seen in 15-20% of patients. See the images below.

Brain meningioma. Nonenhanced CT scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. 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 CT 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. CT scan of the frontal internal table and diploe shows erosion and bone infiltration.

CT can show acute tumor hemorrhage and widened vascular grooves in the calvarium.

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 CT scans shows an isoattenuating sphenoid-wing meningioma. The left sylvian fissure is partially collapsed.

Brain meningioma. CT 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 displays moderate-to-strong homogeneous enhancement in most tumors; see the images below. Steinhoff et al observed a nodular blush in 97%, a mixed inhomogeneous blush in 0.5%, and a ring blush in 1.5%.^{[9 ]}In a study by Naidich of 136 patients, tumor blush was nodular and nearly homogeneous in 70% of patients, inhomogeneous in 24% of patients, and ringlike in 2% of patients.^{[10 ]}

Brain meningioma. Parietal-convexity meningioma. Contrast-enhanced CT scan shows a round, hyperattenuating, and unilobulated mass. Broad-based attachment to the dura is demonstrated, as is intense edema in the subjacent brain.

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.

Peripheral cysts resulting from trapped CSF can be present. See the image below.

Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced CT scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid (arrows), subtle edema, homogeneous enhancement, and ventricular dilation are demonstrated.

Cystic components of the meningiomas may be present inside the tumor or between the tumor and the adjacent brain, so-called trapped CSF.

Degree of Confidence

Meningiomas are well-circumscribed peripheral or falcine masses that deform the brain. About 90% of meningiomas are demonstrated on CT. The main role of CT, as opposed to other imaging modalities, is the demonstration of adjacent bone changes and calcification within the lesion.

Atypical CT features are the primary reason for preoperative misdiagnosis. Posterior fossa meningiomas may be missed by CT, as will be some en plaque lesions. CT can fail to demonstrate cystic changes in intracranial meningiomas. CT 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

Findings

An important advantage of MRI in the imaging of meningiomas is its superior resolution of different types of soft tissue, multiplanar capability, and 3D reconstruction. See the images below.

Parasagittal meningioma. A. Nonenhanced Sagittal T1 weighted shows a solid dural isointense mass with bone invasion and compression against the parietal cortex. B. Contrast enhanced sagittal T1 weighted 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-MRI on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B. MRI reconstruction shows sagittal venous obstruction and 3D appearance of the tumor.

Brain meningioma. Nonenhanced T1-weighted sagittal MRI demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule (arrow) is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone.

Brain meningioma. Nonenhanced axial MRI 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 MRI 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 MRI demonstrates a typical parasagittal meningioma demonstrated. A homogeneous, enhancing, globose mass is depicted.

Brain meningioma. Contrast-enhanced T1-weighted coronal MRI 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 demonstrates posterior fossa and parietal meningiomas. B Gadolinium enhancing on Sagittal T1 weighted shows intense enhancing of the masses. C. T2 coronal shows stable hypointense appearance of the posterior mass after endovascular embolization.

Malignant and multiple meningiomas. White man, 47y/o underwent to Gamma Knife due to left convexity meningioma followed of microsurgical removal of the tumor in 2001. A, B. Four years later -December 2005- MRI showed stable residual parietal/occipital mass. Left sigmoid sinus is occluded. C, D. One small right frontal meningioma was also undergone to 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. While 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).

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. 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.

If gadolinium enhancement is used, keep in mind the following warning. Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). 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.

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. MRI is unreliable for recognition of tumor calcification. Acute hemorrhage is often difficult to image on MRI.

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

Findings

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

Findings

Although magnetic resonance angiography (MRA and 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.

Meningiomas are supplied by meningeal branches of the internal and external carotid artery. Basal meningiomas of the anterior and middle cranial fossa and meningiomas of the wings of the sphenoid bone commonly are supplied by the internal carotid artery. Other supratentorial meningiomas are supplied by the internal and external carotid arteries.

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.

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. 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.

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.

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.^{[14,15 ]}

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 µ of polyvinyl alcohol) 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.

Polyvinyl alcohol (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 MRI 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 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 demonstrates posterior fossa and parietal meningiomas. B Gadolinium enhancing on Sagittal T1 weighted shows intense enhancing of the masses. C. T2 coronal shows stable hypointense appearance of the posterior mass after endovascular embolization.

Malignant and multiple meningiomas. White man, 47y/o underwent to Gamma Knife due to left convexity meningioma followed of microsurgical removal of the tumor in 2001. A, B. Four years later -December 2005- MRI showed stable residual parietal/occipital mass. Left sigmoid sinus is occluded. C, D. One small right frontal meningioma was also undergone to radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated.

A-D. Coronal T2 weighted image and enhanced T1 MR Images demonstrated quick growth of 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 CT. The bone window shows petrous bone destruction and partial lack of bone plane after surgical removal of the tumor.

DSA. A, B. Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C. Occipital artery. D. Those 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 was seen on MRI control of this tumor. Coronal enhanced T1 weighted and FLAIR sequences are shown. C, D. Digital Angiography. Right media meningeal branch demonstrates feeding of the tumor. It was not embolized.

A. 3D-enhanced T1 weighted MRI image shows residual meningioma at the cranial base after second surgical removal. B. Coronal T2 weighted MRI image shows intense edema surrounding the frontal mass. C. 3D image on enhanced T1 MRI image demonstrates frontal meningioma underlying the orbital right sulcus. D. Gadolinium axial T1 weighted image shows one of the three focal hyperintense masses discovered only on this sequence. Brain metastases from meningioma have not been proved.

Histopathologic report describes as a meningothelial-like neoplasm proliferation that shows hypercellularity, a prominent nucleolus, regions of necrosis, occluded veins and arteries, and dense chromatin. The neoformation reaches adjacent bone structures. Histopathologic diagnosis: left temporal mass compatible with an atypical meningioma meningothelial neoplasm.

Medicolegal Pitfalls

• A growing number of lawsuits that name radiologists involve special procedures.
• Good technique, good planning, and informed consent, which includes the involvement of the interventional neuroradiologist, can help physicians prevent most claims.

Multimedia

Media file 1: Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced CT scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid (arrows), subtle edema, homogeneous enhancement, and ventricular dilation are demonstrated.

Media file 2: Brain meningioma. Nonenhanced CT scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. 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.

Media file 3: Brain meningioma. Nonenhanced CT scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown.

Media file 4: Brain meningioma. Malignant frontal-convexity meningioma. CT scan of the frontal internal table and diploe shows erosion and bone infiltration.

Media file 5: Brain meningioma. Nonenhanced CT scans shows an isoattenuating sphenoid-wing meningioma. The left sylvian fissure is partially collapsed.

Media file 6: Brain meningioma. CT 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.

Media file 7: Brain meningioma. Parietal-convexity meningioma. Contrast-enhanced CT scan shows a round, hyperattenuating, and unilobulated mass. Broad-based attachment to the dura is demonstrated, as is intense edema in the subjacent brain.

Media file 8: 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.

Media file 9: Brain meningioma. Nonenhanced T1-weighted sagittal MRI demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule (arrow) is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone.

Media file 10: Brain meningioma. Nonenhanced axial MRI 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.

Media file 11: Brain meningioma. Coronal T2-weighted MRI demonstrates a typical parasagittal meningioma. Isointense and inhomogeneous tumor without peripheral edema indicates a more fibrous and harder character, ie, a fibroblastic meningioma.

Media file 12: Brain meningioma. Contrast-enhanced T1-weighted axial MRI demonstrates a typical parasagittal meningioma demonstrated. A homogeneous, enhancing, globose mass is depicted.

Media file 13: Brain meningioma. Contrast-enhanced T1-weighted coronal MRI shows a typical parasagittal meningioma. A homogeneous, enhancing, globose mass is depicted.

Media file 14: 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.

Media file 15: Brain meningioma. Nonenhanced CT scans 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.

Media file 16: Brain meningioma. Middle fossa meningioma. Contrast-enhanced CT scan depicts a round, inhomogeneous, attenuating, enhancing mass.

Media file 17: Brain meningioma. Middle fossa meningioma. Contrast-enhanced CT scan depicts a dense, enhancing mass.

Media file 18: 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.

Media file 19: Brain meningioma. Cerebellopontine angle meningioma. Off-midline sagittal nonenhanced T1-weighted MRI displays a hypointense and inhomogeneous round mass in the cerebellopontine angle.

Media file 20: Brain meningioma. Cerebellopontine angle meningioma. T2-weighted MRI 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 T2-weighted image indicates a soft tumor consistency and microhypervascularity, which is seen more often in aggressive, angioblastic, or meningothelial meningioma.

Media file 21: Brain meningioma. Cerebellopontine angle meningioma. Selective angiogram of right occipital artery shows focal hypervascularity through the auricular artery. Early and delayed staining is seen.

Media file 22: Brain meningioma. Cerebellopontine angle meningioma. Right occipital artery embolized with polyvinyl alcohol particles before surgery.

Media file 23: Two different cases. A, B. CT scans depict calcified meningiomas from the parietal convexity. C, D. 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. Coronal T2 weighted MRI demonstrates calcium deposit (star) surrounded of solid tissue (small arrow); edema is not seen in this case.

Media file 24: Parasagittal meningioma. A. Nonenhanced Sagittal T1 weighted shows a solid dural isointense mass with bone invasion and compression against the parietal cortex. B. Contrast enhanced sagittal T1 weighted 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.

Media file 25: A. Noncontrast angio-MRI on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B. MRI reconstruction shows sagittal venous obstruction and 3D appearance of the tumor.

Media file 26: Multiple meningiomas: A. Sagittal T1 weighted demonstrates posterior fossa and parietal meningiomas. B Gadolinium enhancing on Sagittal T1 weighted shows intense enhancing of the masses. C. T2 coronal shows stable hypointense appearance of the posterior mass after endovascular embolization.

Media file 27: Malignant and multiple meningiomas. White man, 47y/o underwent to Gamma Knife due to left convexity meningioma followed of microsurgical removal of the tumor in 2001. A, B. Four years later -December 2005- MRI showed stable residual parietal/occipital mass. Left sigmoid sinus is occluded. C, D. One small right frontal meningioma was also undergone to radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated.

Media file 28: A-D. Coronal T2 weighted image and enhanced T1 MR Images demonstrated quick growth of 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."

Media file 29: Coronal CT. The bone window shows petrous bone destruction and partial lack of bone plane after surgical removal of the tumor.

Media file 30: DSA. A, B. Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C. Occipital artery. D. Those branches were embolized before the surgical procedure. The tumor was partially removed due to cranial base involvement.

Media file 31: Frontal meningioma. A, B. Slow growth and surrounding edema was seen on MRI control of this tumor. Coronal enhanced T1 weighted and FLAIR sequences are shown. C, D. Digital Angiography. Right media meningeal branch demonstrates feeding of the tumor. It was not embolized.

Media file 32: A. 3D-enhanced T1 weighted MRI image shows residual meningioma at the cranial base after second surgical removal. B. Coronal T2 weighted MRI image shows intense edema surrounding the frontal mass. C. 3D image on enhanced T1 MRI image demonstrates frontal meningioma underlying the orbital right sulcus. D. Gadolinium axial T1 weighted image shows one of the three focal hyperintense masses discovered only on this sequence. Brain metastases from meningioma have not been proved.

Media file 33: Histopathologic report describes as a meningothelial-like neoplasm proliferation that shows hypercellularity, a prominent nucleolus, regions of necrosis, occluded veins and arteries, and dense chromatin. The neoformation reaches adjacent bone structures. Histopathologic diagnosis: left temporal mass compatible with an atypical meningioma meningothelial neoplasm.

Media file 34: CT scanning is the imaging technique most commonly used to evaluate bone changes and calcium in meningiomas. Plain radiography can show calcium in 20% of patients. This image demonstrates bone changes on a coronal CT scan with bone window settings.

Media file 35: 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.

Media file 36: Meningiomas have the same enhancement appearance on CT scans and MRIs after the injection of contrast material. Meningiomas of the left parietal convexity are shown on axial CT scans, and meningiomas of the left parietal midline are shown on MRIs. Intense enhancement is seen.

Media file 37: MRI is the best cross-sectional imaging modality for assessing soft tissues and thus brain tumors, including specifically meningiomas. On coronal T2-weighted MRIs, parasagittal meningiomas are isointense and inhomogeneous tumors regarding fibrous and have a harder character (fibroblastic meningioma).

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Keywords

meningioma of the brain, meningothelioma, leptomeningioma, mesothelioma of the dura mater

Contributor Information and Disclosures

Author

German C Castillo, MD, FACR. FICS, Assistant Professor, Department of Diagnostic and Interventional Radiology, Harvard Clinic and Central University of Ecuador
German C Castillo, MD, FACR. FICS is a member of the following medical societies: American Roentgen Ray Society, International College of Surgeons, and Radiological Society of North America
Disclosure: Nothing to disclose.

Medical Editor

Jeffrey L Creasy, MD, Associate Professor, Associate Section Head, Division of Neuroradiology, Director, Neuroradiology Fellowship, Department of Radiology, Vanderbilt University
Jeffrey L Creasy, MD is a member of the following medical societies: American College of Radiology, American Society of Neuroradiology, and Radiological Society of North America
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Val Runge, MD, Robert and Alma Moreton Centennial Chair in Radiology, Professor, Editor-in-Chief of Investigative Radiology, Department of Radiology, Scott and White Clinic and Hospital
Val Runge, MD is a member of the following medical societies: Society for Health and Human Values
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics; Program Director, Diagnostic Imaging Program, Center for Neuroscience and Regenerative Medicine (CNRM), Uniformed Services University of the Health Sciences
James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Head and Neck Radiology, American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

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