You are in: eMedicine Specialties > Radiology > BRAIN/SPINE Meningioma, BrainArticle Last Updated: Apr 27, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  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 is a member of the following medical societies: American Roentgen Ray Society, International College of Surgeons, and Radiological Society of North America Editors: Jeffrey L Creasy, MD, Associate Professor, Associate Section Head, Division of Neuroradiology, Director, Neuroradiology Fellowship, Department of Radiology, Vanderbilt University; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Carlos Lozada; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences Author and Editor Disclosure Synonyms and related keywords: meningothelioma, leptomeningioma, mesothelioma of the dura mater INTRODUCTIONSection 2 of 12
  BackgroundMeningiomas 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. 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. PathophysiologyMeningiomas 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 imbedded in the dura, while intraventricular tumors arise from pia-arachnoid rests. Meningiomas occur more frequently where the villi usually are most numerous, ie, along the major dural venous sinus. The tumors typically have a definite dural attachment. FrequencyUnited StatesIn 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.1 InternationalMeningiomas constituted 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 technologiesThe 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 ring worm 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/MorbiditySurvival rates from surgical series are 82%, 72%, and 60% at 2, 5, and 10 years, respectively.
RaceDuring 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.
SexMeningiomas 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.
AgeMeningiomas have a predilection to occur from the third to sixth decades of life, with a peak incidence occurring in individuals aged approximately 45 years.
AnatomyMeningiomas 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%). Clinical DetailsExcept 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:
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) it is mainly used for small (<3 cm in diameter) residual, recurrent or tentorial meningiomas. The relatively low minimum tumor radiation dose for skull base menigiomas provide low morbidity. Radiosurgery now is able for providing 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 GK may be a safe adjunct to other treatment modalities. Radiosurgery 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 has been suggested in recent reports that can cause regression of unresectable and recurrent meningiomas.Surgical remove of the tumor, radiation therapy, radiosurgery and/or growth-modifying drugs may contribute to the best outcome of the meningiomas. Preferred ExaminationMRI 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 TechniquesCT 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. Patients with pacemakers currently cannot be evaluated by means of MRI. Other contraindications to MRI include some brain aneurysm clips and heart valves. The reader is referred to more detailed texts for a complete list of contraindications to MRI. The presence of calcifications and adjacent bony changes are best evaluated by using CT, as MRI is poor in this regard. DIFFERENTIALSSection 3 of 12
Astrocytoma, Brain Brain, Cavernous Angiomas Neurofibromatosis Type 2 Sarcoid, CNS Tuberculosis, CNS Other Problems to Be ConsideredDural vascular malformation
RADIOGRAPHSection 4 of 12
FindingsIn 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 ConfidenceMost 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/NegativesCalcification within the tumor is a considerably less frequent plain radiographic manifestation; therefore, false-negative results occur. Most patients with brain meningiomas do not undergo x-ray imaging because the diagnosis has been made directly by using CT or MRI. CT SCANSection 5 of 12
FindingsCT scanning has several advantages in the imaging of meningiomas. Invasion of surrounding dura frequently provokes an osteoblastic response, causing hyperostosis. CT is the imaging modality used best for demonstrating calcification of meningiomas (see Image 15,23). The CT nature of the calcification may be nodular, fine and punctate, or dense. Histologic studies have demonstrated calcification in up 45% of meningiomas. CT is effective in showing hyperostosis, bone destruction, and erosion at the site of the dural attachment (see Images 2-4). Hyperostosis is seen in 15-20% of patients. 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 (see Images 5-6). 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. Contrast-enhanced CT displays moderate-to-strong homogeneous enhancement in most tumors (see Images 7-8). Steinhoff et al observed a nodular blush in 97%, a mixed inhomogeneous blush in 0.5%, and a ring blush in 1.5%. 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 (see Images 2-4). Peripheral cysts resulting from trapped CSF can be present (see Image 1). Cystic components of the meningiomas may be present inside the tumor or between the tumor and the adjacent brain, so-called trapped CSF (see Image 2). Degree of ConfidenceMeningiomas 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/NegativesFalse-negative findings can occur with cystic changes in brain meningiomas. False-positive findings can occur with large dural calcification, which can mimic the disease. MRISection 6 of 12
FindingsAn important advantage of MRI in the imaging of meningiomas is its superior resolution of different types of soft tissue, and its multiplanar capability,, MR angio, and 3D reconstrucction. (see Images 24-25). MRI can demonstrate tumor vascularity, arterial encasement, venous sinus invasion, and the relationship between the tumor and surrounding structures. It 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 (see Images 9-13). 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 (see Images 11-13). T2-images also show the extent of edema. Multiple meningioma occurred between 5-40% (see Images 26-27). 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 (see Images 9-10). 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 extraaxial mass it may show meningeal cysts, ring enhancement, fatty transformation, and en plaque morphology. Malignant meningioma may invade the calvarium and cerebral parenchyma 1%). Most of the meningiomas can be diagnosed by MRI, however 1HMRSI can yield more informative about metabolic materials changes in tumor cells. MRS reveals lactate in embolized areas of the meningioma immediately after embolization. Lipids are not observed before the 3rd 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 (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. 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. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. 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;yellowspots 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 ConfidenceIn 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/NegativesFalse-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. ULTRASOUNDSection 7 of 12
FindingsThe 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. ANGIOGRAPHYSection 8 of 12
FindingsAlthough 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 Image 14). Recently, as an alternative to traditional catheter angiography, 3-dimensional 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 ConfidenceAngiography 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/NegativesArterial 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. INTERVENTIONSection 9 of 12
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. Currently, 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 size ranged from 100 to 2000 microns ( Biodyne, Ivalon, Contour Emboli) have been used, but the newer class of deformable particles (Embospheres (Microsphere) and Bead Block (Terumo) are 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 that will be soon reported. 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 Images 20-22,26-33). Medical/Legal Pitfalls
TEST QUESTIONSSection 10 of 12
MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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