Revision 217 for 'Meningioma'

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Meningiomas are extra-axial tumors and represent the most common tumor of the meninges. They are a non-glial neoplasm that originates from the meningocytes or arachnoid cap cells of the meninges, and are located anywhere that meninges are found, and in some places where only rest cells are presumed to be located. Although they usually easily diagnosed, and are typically benign with a low rate of recurrence following surgery, there are a large number of histological variants with variable imaging features and in some instances more aggressive biological behavior. 

A broad division of meningiomas is into primary intradural (which may or may not have secondary extradural extension) and primary extradural (rare) 18.  They can also be classified according to location (e.g. spinal, intraosseous, intraventricular etc.), by histological variants (e.g. clear cell, rhabdoid etc.) and by etiology (e.g. radiation induced etc.). 

Typical meningiomas appear as dural based masses isointense to grey matter on both T1 and T2 weighted imaging, and demonstrate vivid contrast enhancement on both MRI and CT. Some of the aforementioned variants can, however, vary dramatically in their imaging appearance.

This article is a general discussion of meningioma focusing on typical primary intradural meningiomas and the imaging findings of intracranial disease. For spinal and primary extradural tumors refer to spinal meningioma and primary extradural meningioma articles respectively. Many of the  histological variants are also discussed separately. 


Meningiomas are more common in women, with a ratio of 2:1 intracranially and 4:1 in the spine. Atypical and malignant meningiomas are slightly more common in males. They are uncommon in patients before the age of 40 and should raise suspicion of neurofibromatosis type 2 (NF2) when found in young patients.

Clinical presentation

Many small meningiomas are found incidentally and are entirely asymptomatic. Often they cause concern as they are mistakenly deemed to be the cause of vague symptoms, most frequently headaches. Larger tumors or those with adjacent edema or abutting particularly sensitive structures can present with a variety of symptoms. Most common presentations include 8:

  • headache: 36%
  • paresis: 22%
  • change in mental status: 21%

Meningiomas may also become clinically apparent due to mass effect their location:

Occasionally transosseous or intraosseous involvement with prominent hyperostosis may result in local mass effect (e.g. proptosis). 

It should be noted that although dural venous sinus invasion and occlusion is not infrequent, as this usually this occurs very gradually most are asymptomatic, as collateral veins have had time to enlarge. 


Meningiomas are thought to arise from meningocytes or arachnoid cap cells, which themselves arise from pluripotential mesenchymal progenitor cells, which accounts for sometimes unusual location of primary extradural tumors 18-19

Although the majority of tumors are sporadic, they are also seen in the setting of previous cranial irradiation and of course in patients with neurofibromatosis type II (NF2) (Merlin gene on Chromosome 22). Additionally meningiomas demonstrate estrogen and progesterone sensitivity and may grow during pregnancy.


Grading of meningiomas follows the WHO classification for CNS tumors  and includes both usual histological features ( e.g. mitotic index) as well as a number of histological subtypes, some of which have been associated with more aggressive behavior 7, 11, 23:

* Hemangiopericytomas were, until 1993, considered angiomatous meningiomas, but are not classified as a separate entity; "Other neoplasms related to the meninges" according to WHO 2007 classification of CNS tumors

** It is important to note, when reading older literature, that in the WHO 2007 classification, infiltration into brain parenchyma of an otherwise "benign" grade I tumor was sufficient to designate it a grade II tumor. As such, incidence of grade II tumors increased to ~30% 11.


In general, there are two main macroscopic forms easily recognized on image studies:

  • globose: rounded, well defined dural masses, likened to the appearance of a fried egg seen in profile (the most common presentation)
  • en plaque: extensive regions of dural thickening

The cut surface reflects the various histologies encountered, ranging from very soft to extremely firm in fibrous or calcified tumors. They are usually light tan in coloring, although again this will depend on histological subtypes. 

Radiographic features

In addition to histological variants, many of which have 'atypical' imaging appearances, a number of 'special examples' of meningiomas are best discussed separately. These include: 

The remainder of this section focuses on more typical imaging appearances of run-of-the-mill meningiomas. 

Plain radiography

Plain films no longer have a role in the diagnosis or management of meningiomas. Historically a number of features were observed, including:

  • enlarged meningeal artery grooves
  • hyperostosis or lytic regions
  • calcification
  • displacement of calcified pineal gland / choroid plexus due to mass effect

CT is often the first modality employed to investigate neurological signs or symptoms, and often is the modality which detects an incidental lesion:

  • non-contrast CT
    • 60% slightly hyperdense to normal brain, the rest are more isodense
    • 20-30% have some calcification 8
  • post-contrast CT
    • 72% brightly and homogeneously contrast enhance 8
    • malignant or cystic variants demonstrate more heterogeneity / less intense enhancement {ref needed}
  • hyperostosis (5%) 23
    • typical for meningiomas that abut the base of the skull
    • need to distinguish reactive hyperostosis from:
  • enlargement of the paranasal sinuses (pneumosinus dilatans) has also been suggested to be associated with anterior cranial fossa meningiomas 20
  • lytic / destructive regions are seen particularly in higher grade tumors, but should make one suspect alternative pathology (e.g. hemangiopericytoma or metastasis) {ref needed}

As is the case with most other intracranial pathology, MRI is the investigation of choice for the diagnosis and characterization of meningiomas. When appearance and location is typical, the diagnosis can be made with a very high degree of certainty. In some instances, however, the appearances are atypical and careful interpretation is needed to make a correct preoperative diagnosis. 

Meningiomas typically appear as extra-axial masses with a broad dural base. They are usually homogeneous and well circumscribed, although many variants are encountered.

Signal characteristics

Signal characteristics of typical meningiomas include:

  • T1
    • isointense to grey matter (60-90%) 3,8, 13
    • hypointense to grey matter (10-40%): particularly fibrous, psammomatous variants
  • T1 C+ (Gd): usually intense and homogeneous enhancement
  • T2
    • isointense to grey matter (~50%) 3,8,13
    • hyperintense to grey matter (35-40%)
      • usually correlates with soft texture and hypervascular tumors 13
      • very hyperintense lesions may represent the microcystic variant 12
    • hypointense to grey matter (10-15%): compared to grey matter and usually correlates with harder texture and more fibrous and calcified contents
  • DWI/ADC: atypical and malignant subtypes may show greater than expected restricted diffusion although recent work suggests that this is not useful in prospectively predicting histological grade 15-16
  • MR spectroscopy: Usually it does not play a significant role in diagnosis but can help distinguish meningiomas from mimics. Features include:
    • increase in alanine (1.3-1.5 ppm)
    • increased glutamine/glutamate
    • increased choline (Cho): cellular tumor
    • absent or significantly reduced N-acetylaspartate (NAA): non-neuronal origin
    • absent or significantly reduced creatine (Cr)
  • MR perfusion:  good correlation between volume transfer constant (k-trans) and histological grade {ref needed}
Helpful imaging signs

A number of helpful imaging signs have been described, including:

  • CSF vascular cleft sign, which is not specific for meningioma, but helps establish the mass to be extra-axial; loss of this can be seen in grade II and grade III which may suggest brain parenchyma invasion
  • dural tail seen in 60-72% 2 (note that a dural tail is also seen in other processes)
  • sunburst or spokewheel appearance of the vessels
  • arterial narrowing
    • typically seen in meningiomas which encase arteries
    • useful sign in parasellar tumors, in distinguishing a meningioma from a pituitary macroadenoma; the later typically does not narrow vessels

More than half of the meningiomas demonstrate variable amount of vasogenic edema in adjacent brain parenchyma 24. Correlation between age, gender, tumor size, rapid growth, location (convexity and parasagittal > elsewhere), histologic type, and invasion in the case of malignant meningiomas has been suggested in literature but not yet confirmed. The underlying mechanisms are most likely multifactorial however it has been shown that there is a strong association between the presence and severity of the vasogenic edema and expression of the vascular endothelial growth factor (VEGF) 17:

  • venous stasis/occlusion/thrombosis
  • compressive ischemia
  • aggressive growth/invasion
  • parasitisation or pial vessels
  • histologic subtype: secretory meningioma  25 
  • vascular endothelial growth factor (VEGF): produced with the meningioma and enters the adjacent parenchyma 
Angiography (DSA)

Catheter angiography is rarely now of diagnostic use, but rather is performed for preoperative embolization to reduce intraoperative blood loss. This is especially useful for skull base tumors, or those thought to be particularly vascular (e.g. microcystic variants or those with very large vessels). Particles are favored typically 7-9 days prior to surgery. {ref needed}

Meningiomas can have dual blood supply. The majority of tumors are predominantly supplied by meningeal vessels; these are responsible for the sunburst or spokewheel pattern observed on MRI / DSA. Some tumors also have significant pial supply to the periphery of the tumor. {ref needed}

A well known angiographic sign of meningiomas is the mother-in-law sign, in which the tumor contrast blush "comes early, stays late, and is very dense". 

Treatment and prognosis

Treatment is usually with surgical excision. If only incomplete resection is possible (especially at the base of skull) then external-beam radiation therapy can be used 8.

The Simpson grade correlated the degree of surgical resection completeness with with symptomatic recurrence.

Recurrence rate varies with grade and length of follow-up 8, 21

  • grade I = 7-25%
  • grade II = 29-52%
  • grade III = 50-94%

Metastatic disease is rare, but has been reported 8.

History and etymology

The term "meningioma" was first introduced by Harvey Cushing, neurosurgeon, in 1922 9,23.

Differential diagnosis

The differential diagnosis generally includes other dural masses as well as some location specific entities. 

The main dural masses to consider include: 

Specific location differentials include: 

In the setting of hyperostosis consider:

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