Nonenhanced computed tomography scan shows a hyperdense mass resulted in midline shift to the right aspect in the left frontal lobe
CECT shows a homogeneous enhancing mass located in the left frontal lobe.
DSA, Left external carotid artery injection shows early stain of the mass
DSA: hypervascular tumor blush throughout the late arterial phase
DSA: DSA: Left external carotid artery shows delayed stain of the mass
DSA: Left external carotid artery shows delayed stain of the mass

Meningioma

By mahyar


History: 50 Y/O female with headache


Findings:

CT 1: Nonenhanced computed tomography scan shows a hyperdense mass resulted in midline shift to the right aspect in the left frontal lobe :: CT 1 ::
Nonenhanced computed tomography scan shows a hyperdense mass resulted in midline shift to the right aspect in the left frontal lobe







CT 2: CECT shows a homogeneous enhancing mass located in the left frontal lobe. :: CT 2 ::
CECT shows a homogeneous enhancing mass located in the left frontal lobe.







Fluoroscopy 1: DSA, Left external carotid artery injection shows early  stain of the mass :: Fluoroscopy 1 ::
DSA, Left external carotid artery injection shows early stain of the mass







Fluoroscopy 2: DSA: hypervascular tumor blush throughout the late arterial phase :: Fluoroscopy 2 ::
DSA: hypervascular tumor blush throughout the late arterial phase







Fluoroscopy 3: DSA: DSA: Left external carotid artery shows  delayed stain of the mass :: Fluoroscopy 3 ::
DSA: DSA: Left external carotid artery shows delayed stain of the mass







Fluoroscopy 4: DSA: Left external carotid artery shows  delayed stain of the mass :: Fluoroscopy 4 ::
DSA: Left external carotid artery shows delayed stain of the mass









Discussion:
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.
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.
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.

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.


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.


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.
Tumors of the meningioma group are usually very vascular and often produce enlargement of the arteries that supply them. The most characteristic vascular finding of a meningioma is a contribution to the blood supply of the neoplasm by branches of the external carotid system. Whenever it is possible to show that the external carotid artery shares in the blood supply of an intracranial tumor, it is most likely to be a meningioma. On the other hand, cranial tumors that invade the meninges may have an evident blood supply in the angiograph from a branch of the external carotid artery; however, bone destruction is usually also evident. Metastatic tumor invading the bones or the meninges and even gliomas that become exophytic may exhibit such a finding.
1. Enlarged vascular supply
With a meningioma, the artery that most often becomes enlarged is the middle meningeal (or its branches) and the other meningeal arteries.
After a meningioma has evoked a reaction of the outer periosteum of the skull, the superficial temporal, or some other extracranial branches of the external carotid artery will participate in the tumor blood supply. In attempting to determine whether the external carotid artery is indeed involved in the supply of a tumor, it is essential to pay careful attention to the relative sizes of the branches of the middle meningeal artery, in particular. It should be determined if possible, whether small branches enter the tumor area from an apparently enlarged artery.
Several routine steps may be helpful to determine whether a branch of the external carotid artery is or is not supplying a tumor. First, the size of the trunk of the middle meningeal artery should be scrutinized. If there is an increased blood flow through the middle meningeal trunk (which is necessary to supply a tumor) the artery usually becomes tortuous in its initial portion before it bifurcates. The presence of tortuosity per se is not necessarily an indication of an increased blood flow through this artery. Some patients have a tortuous initial portion of the middle meningeal artery without having a neoplasm, but, if the tortuous segment is longer than I or 2 cm, it is probably pathologic.Second, the relative sizes of the various branches of the middle meningeal artery should be noted since a branch involved in the supply of a tumor will fill slightly earlier and be larger than the other branches. Third, a branch to a meningioma may not appear to be enlarged at its origin from the middle meningeal trunk; if the artery is followed to its periphery, however, it will be noted that, instead of getting smaller, it actually becomes larger as it approaches the region of the neoplasm. It is observed chiefly in the external carotid circulation, and rarely in the internal carotid system.
Such a finding is an important sign of blood supply of a tumor and is believed to be due to a reversal of blood flow in the many arterioles which anastomose within the meninges and the bone. They may join a principal vessel feeding the tumor, preceding either from an adjacent branch of the middle meningeal, from accessory meningeal branches, or from superficial temporal arteries involved in the blood supply of the bone.
By virtue of this reversal of flow, more blood is drawn into the final segment of the artery to increase the blood supply of the neoplasm. Finally, a careful search should be made for multiple branches arising from any vessel in question, especially near its termination. Such branches may be very inconspicuous, or they may be extremely prominent.
When external carotid angiography alone is performed, the abnormal vessels are easier to visualize than when there is superimposition of branches of the internal carotid artery. The term sunburst appearance has been applied to this very distinctive angiographic finding which is characteristic of meningiomas but also seen in certain other vascular neoplasms, such as hemangiopericytomas. It is believed that the sunburst appearance is due to a radial distribution of the small arterial branches which seem to spring from a central point which probably represents the original site from which the blood supply was drawn at the beginning of the growth of the tumor.
After a meningioma has evoked a reaction of the outer periosteum of the skull, the superficial temporal, or some other extracranial branches of the external carotid artery will participate in the tumor blood supply. In attempting to determine whether the external carotid artery is indeed involved in the supply of a tumor, it is essential to pay careful attention to the relative sizes of the branches of the middle meningeal artery, in particular. It should be determined if possible, whether small branches enter the tumor area from an apparently enlarged artery.
Several routine steps may be helpful to determine whether a branch of the external carotid artery is or is not supplying a tumor. First, the size of the trunk of the middle meningeal artery should be scrutinized. If there is an increased blood flow through the middle meningeal trunk (which is necessary to supply a tumor) the artery usually becomes tortuous in its initial portion before it bifurcates. The presence of tortuosity per se is not necessarily an indication of an increased blood flow through this artery. Some patients have a tortuous initial portion of the middle meningeal artery without having a neoplasm, but, if the tortuous segment is longer than I or 2 cm, it is probably pathologic.Second, the relative sizes of the various branches of the middle meningeal artery should be noted since a branch involved in the supply of a tumor will fill slightly earlier and be larger than the other branches . Third, a branch to a meningioma may not appear to be enlarged at its origin from the middle meningeal trunk; if the artery is followed to its periphery, however, it will be noted that, instead of getting smaller, it actually becomes larger as it approaches the region of the neoplasm. It is observed chiefly in the external carotid circulation, and rarely in the internal carotid system.
Such a finding is an important sign of blood supply of a tumor and is believed to be due to a reversal of blood flow in the many arterioles which anastomose within the meninges and the bone. They may join a principal vessel feeding the tumor, proceeding either from an adjacent branch of the middle meningeal, from accessory meningeal branches, or from superficial temporal arteries involved in the blood supply of the bone.
2. The sunburst appearance
By virtue of this reversal of flow, more blood is drawn into the final segment of the artery to increase the blood supply of the neoplasm. Finally, a careful search should be made for multiple branches arising from any vessel in question, especially near its termination. Such branches may be very inconspicuous, or they may be extremely prominent.
When external carotid angiography alone is performed, the abnormal vessels are easier to visualize than when there is superimposition of branches of the internal carotid artery. The term sunburst appearance has been applied to this very distinctive angiographic finding which is characteristic of meningiomas but also seen in certain other vascular neoplasms, such as hemangiopericytomas.It is believed that the sunburst appearance is due to a radial distribution of the small arterial branches which seem to spring from a central point which probably represents the original site from which the blood supply was drawn at the beginning of the growth of the tumor.
The majority of meningiomas that occur over the cranial vault are supplied by branches of the middle meningeal artery and, as explained above, sometimes by the superficial temporal artery. Some meningiomas situated in the frontal fossa may be supplied by meningeal branches which normally feed the bone in this region and which arise from or anastomose with branches of the ophthalmic artery. Since the circulation through the internal carotid artery is swifter than the external, eventually a significant proportion of (or most of) the tumor blood supply may be by way of the ophthalmic artery. This vessel then becomes enlarged. In such cases it is possible to demonstrate angiographically branches arising from the superior aspect of the ophthalmic artery and extending upward to the roof of the orbit. Falx meningiomas arising in the frontal region (back to the coronal suture) may receive their blood supply partly from the anterior meningeal (artery of the falx) branch of the ophthalmic artery. The anterior meningeal artery (arising from the anterior ethmoidal branch of the ophthalmic) may become enlarged and can be followed along the inner table of the skull in the frontal region Although frontal midline meningiomas and subfrontal (olfactory groove) meningiomas usually derive their blood supply from the ophthalmic artery, tuberculum sellae meningiomas often do not have a principal ophthalmic supply.
Some tentorial meningiomas present another example of blood supply through the internal carotid artery, by way of its meningeal anastomotic branches. The tumor also receives branches from the external carotid system.
Meningiomas in the posterior fossa also may be supplied by accessory meningeal arteries. These are branches of the external carotid system entering the skull by way of the condyloid foramen and through the foramen lacerum. Anterior and posterior meningeal branches of the vertebral arteries also supply such lesions.
Branches of the middle meningeal and superficial temporal arteries sometimes overlie the area of a neoplasm, but this does not necessarily mean that they are supplying the lesion . The rules explained above, especially progressive vascular enlargement (paradoxical enlargement), should be followed in trying to evaluate the significance of vessels in, or about, a tumor area.
An occasional branch of the external carotid artery, most often the superficial temporal artery, may appear to enlarge on the late films of serialogram. It is necessary, however, to differentiate between actual enlargement of a vascular segment and its apparent enlargement which may be caused by laminar flow. The main stream of contrast substance is through the center of the artery, and the periphery of the vessel becomes opacified after the center. The later of two films may therefore show an arterial diameter which appears to be larger than on the earlier film. In addition, some enlargement may be a true vasodilatation due to the effect of the contrast material on the vessel wall. The angiogram usually serves to differentiate such an appearance from true enlargement.
3. The vascular rim
Not all meningiomas are supplied principally by the external carotid artery and its branches. A significant number are supplied by both the external and the internal carotid arteries .In this case the periphery of the meningioma is supplied by branches from the internal carotid system that encircle the tumour and form the characteristic vascular rim,while the center of the tumour is supplied by branches from the external carotid system that radiated peripherally forming the sunburst appearance,and a small percentage draw exclusively from intracranial branches of the internal carotid artery. An example of exclusive internal carotid supply is the intraventricular meningioma, a tumor which is usually fed by the choroidal arteries
4. The venous blush
Although the vessel or vessels that actually supply a meningioma can usually be seen in the angiogram, sometimes they cannot, and only a large area of abnormal density can be discerned. The intrinsic vascularity of a tumor has previously been referred to as the “tumor cloud,” “stain,” or “capillary blush.” A homogeneous tumor cloud in which there is a fairly even distribution of the contrast material throughout the tumor is characteristic of meningiomas. In addition, persistence of the tumor cloud for a considerable period of time throughout the serialogram is of great importance in the diagnosis of meningiomas.
The stain may still be visible even on the last film taken 8 or 9 sec after the beginning of the injection.
Meningiomas usually exhibit a homogeneous cloud, but it must be appreciated that the stain can develop piecemeal; i.e., only a portion of the tumor may be opacified by one injection. It is not uncommon for one segment of the lesion to be supplied by the ipsilateral external carotid artery and for the remainder of the tumor to draw from the internal carotid artery, or fill via a branch of the contralateral external carotid system. Three (or more) parts of the tumor may fill from different systems. The better the tumor vessels are demonstrated by multiple selective arterial injections, the more fragmented the capillary blush. Therefore, it is necessary to visualize all possible afferent arteries of a meningioma, and mentally combine the stains, to gain a true concept of the size and location of the total tumor cloud. The supply to the hilus of a meningioma is virtually always from the external carotid system.
The intrinsic vascular outline of meningiomas is most often sharply circumscribed and lobulated in configuration. This characteristic is in contradistinction to some gliomas (usually mixed oligodendrogliomas and astrocytomas), which may present a homogeneous cloud but are not sharply circumscribed.
Meningiomas usually fail to exhibit prominent draining veins. With some meningiomas, thin veins may be seen at the periphery of the tumor. Some cases of angioblastic meningiomas may present numerous large veins with an increase in the speed of circulation through the tumor that produces early venous filling, similar to that seen with malignant tumors. Such lesions, however, that display draining veins, may exhibit all of the other characteristics of meningiomas. In these cases, the draining vessels are usually superficial cerebral veins. Deep veins may sometimes drain into the vein of Galen. Such veins indicate that there is invasion of brain tissue by the meningioma or, at least, that “tumor” vessels have appeared which bridge the space to the surface of the brain. Intraventricular tumors, of necessity, must drain by way of the tributaries of the thalamostriate and internal cerebral veins.
In trying to evaluate the importance of the above described characteristics of the abnormal circulation of meningiomas, the most significant features are considered to be:(I) a blood supply from the external carotid system, (2) a homogeneous but sharply circumscribed cloud, and (3) the persistence of the contrast substance within the tumor. In some cases, no blood supply can be traced from the external carotid artery into the meningioma, and a diagnosis must be based on other observations. Of the latter two findings, persistence of the tumor cloud appears to be slightly more reliable than homogeneity alone.
Because of pressure on superficial cerebral veins, slowing of the circulation through the area of a meningioma may be seen in the absence of abnormal vascularity. The surface veins in the tumor area fill later than normal, owing to local slowing of the circulation. The finding is nonspecific and may be found in cases of intracerebral tumors, as well.
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.
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.




Differential diagnosis: astrocytoma, dural vascular malformation

Diagnosis confirmation: Surgery / Histo



Category: Neuro

Region / Organ: Head-Brain and brain nerves

Etiology: neoplastic

References:
1) German C Castillo, Imaging in Brain Meningioma, emedicine.medscape
2) Yasser Metwally, Angiography of meningiomas, yassermetwally.wordpress.com/2009/07/09/angiography-of-meningiomas
3) Metwally, MYM: Textbook of neuroimaging, A CD-ROM publication, (Metwally, MYM editor) WEB-CD agency for electronic publication, version 10.3a July 2009
4)C Manelfe, P Lasjaunias, and J Ruscalleda, Preoperative embolization of intracranial meningiomas, AJNR Am. J. Neuroradiol., Sep 1986; 7: 963 - 972.




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