Dr Tee Yu Jin and A.Prof Frank Gaillard et al.

Meningiomas are extra-axial tumours and represent the most common tumour 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 are 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 behaviour.

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

Typical meningiomas appear as dural-based masses isointense to grey matter on both T1 and T2 weighted imaging enhancing vividly on both MRI and CT. Some of the variants as mentioned earlier can, however, vary dramatically in their imaging appearance.

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

Rarely (e.g. 1-2% of cases 27) meningiomas may also arise at ectopic sites (ectopic primary meningioma) such as in head and neck, orbit, nose, paranasal sinus, oropharynx and even places such as the lung.

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 when found in young patients.

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 tumours or those with adjacent oedema 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 depending on their location:

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

Although dural venous sinus invasion and occlusion does occur, it usually occurs very gradually. Therefore most cases of venous invasion 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 the sometimes unusual location of primary extradural tumours 18,19.

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

Grading of meningiomas follows the WHO classification for CNS tumours 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 behaviour 7,11,23:

* Haemangiopericytomas was, until 1993, considered angiomatous meningiomas, but in 2007 WHO classification of CNS tumours they were classified as a separate entity under "Other neoplasms related to the meninges". This again changed in 2016 when the classification was updated. Haemangiopericytomas and solitary fibrous tumours of the dura are considered different manifestations of the same disease, listed under "mesenchymal, non-meningothelial tumours" as a single entry. 

** 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 tumour was sufficient to designate it a grade II tumour. As such, the incidence of grade II tumours increased to ~30% 11.

In general, there are two main macroscopic forms easily recognised in imaging 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 tumours. They are usually light tan in colouring, although again this will depend on histological subtypes.

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 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
  • 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 tumours but should make one suspect alternative pathology (e.g. haemangiopericytoma or metastasis) ref

As is the case with most other intracranial pathology, MRI is the investigation of choice for the diagnosis and characterisation of meningiomas. When appearance and location are 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 of typical meningiomas include:

  • T1
    • usually 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
    • usually isointense to grey matter (~50%) 3,8,13
    • hyperintense to grey matter (35-40%)
    • 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:
  • MR perfusion: good correlation between volume transfer constant (k-trans) and histological grade 28

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

  • CSF 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 is seen in 60-72% 2 (note that a dural tail is also seen in other processes)
  • sunburst or spoke-wheel appearance of the vessels
  • white matter buckling sign
  • arterial narrowing
    • typically seen in meningiomas which encase arteries
    • useful sign in parasellar tumours, in distinguishing a meningioma from a pituitary macroadenoma; the latter typically does not narrow vessels

More than half of the meningiomas demonstrate a variable amount of vasogenic oedema in adjacent brain parenchyma 24. Correlation between age, gender, tumour size, rapid growth, location (convexity and parasagittal > elsewhere), histologic type, and invasion in the case of malignant meningiomas have been suggested in literature but not yet confirmed. Although in general, the presence of severe adjacent oedema is considered more compatible with aggressive meningiomas, in some histologically benign types such as secretory type, oedema can be disproportionately larger than the small tumour size.

The underlying mechanism is most likely multifactorial however it has been shown that there is a strong association between the presence and severity of the peritumoral vasogenic oedema (i.e. oedema index) and expression of the vascular endothelial growth factor (VEGF) or expression of CEA and CK 17,25.

List of some of the proposed underlying mechanisms are:

  • venous stasis/occlusion/thrombosis
  • compressive ischaemia
  • aggressive growth/invasion
  • parasitisation of pial vessels
  • histologic subtype: secretory meningioma 25
  • vascular endothelial growth factor (VEGF): produced within the meningioma that enters the adjacent parenchyma
  • expression of CEA and CK

Catheter angiography is rarely now of diagnostic use but rather is performed for preoperative embolisation to reduce intraoperative blood loss and alleviate resection of a tumour. This is especially useful for skull base tumours, or those thought to be particularly vascular (e.g. microcystic variants or those with very large vessels). Particles are favoured typically 7-9 days prior to surgery although there are not free of complication particularly one study showed a high prevalence of complications associated with particles smaller than 45–150 μm, so risks and benefits should be thoroughly assessed 26.

Meningiomas can have a dual blood supply. The majority of tumours are predominantly supplied by meningeal vessels; these are responsible for the sunburst or spoke-wheel pattern observed on MRI/DSA. Some tumours also have a significant pial supply to the periphery of a tumour.

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

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

The Simpson grade correlates the degree of surgical resection completeness 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.

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

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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Article information

rID: 1659
Synonyms or Alternate Spellings:
  • Meningioma - general
  • Meningiomata
  • Meningiomas

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Cases and figures

  • Figure 1: gross pathology
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  • Case 1: falcine meningioma
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  • Case 2: olfactory groove meningioma
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  • Case 3: frontal meningioma
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  • Case 4
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  • Case 5: intraventricular meningioma
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  • Case 6
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  • Case 7: cerebellopontine angle meningioma
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  • Case 8
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  • Case 9: dural tail
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  • Case 10
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  • Case 11: multiple meningiomas and schwannomas (NF2)
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  • Case 12
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  • Case 13: petrous ridge meningioma
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  • Case 14: posterior fossa meningioma
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  • Case 15: suprasellar meningioma
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  • Case 16
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  • Case 17
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  • Case 18: clivus meningioma
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  • Case 19: chordoid meningioma
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  • Case 20
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  • Case 21
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  • Case 22
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  • Case 23
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