Brief revision of different imaging findings in typical and atypical intracranial meningioma.

1. Imaging of intracranial
meningioma
Dr. Hazem Abu Zeid Yousef
Lecturer of Diagnostic Radiology

2. Background
Meningiomas are the most common non-glial
tumours of the CNS accounting for between 16 -
20 % of all intracranial tumours.
They have been classified into three basic
categories.
The largest one includes tumors growing within
the neuraxis called primary neuraxial
meningiomas (PNM).

3. The second group includes tumors that grow
outside the neuraxis referred to as primary
extraneuraxial meningiomas (PEM) and the third
group comprises tumors extending directly
outside the neuraxis or metastasize and called
secondary meningiomas.

4. Symptomatic meningiomas occur 2–3 times
more often in female patients, especially during
middle-age.
Tumor location is the single most important
feature regarding therapy since it practically
defines the terms of surgical intervention.

5. The frequency of meningiomas at various
intracranial sites varies from study to study. In
general, the convexity and parasagittal
meningiomas tend to occur for approximately
50% of all intracranial meningiomas, while
sphenoid ridge meningiomas account for about
20% the anterior cranial fossa for 10% and those
of parasellar regions for approximately 10%

7. According to the WHO 2007 classification
system, the meningiomas are classified into 3
histological grades and 15 subtypes. Most
meningiomas are benign, well-circumscribed,
slow growing tumors corresponding to WHO
grade I. Some meningiomas, including WHO
grade II atypical (4.7% to 7.2%) and grade III
anaplastic (1.0 to 2.8%) tumors, are clinically
and histologically aggressive.

8. Much larger proportion, 20% of meningioma,
demonstrates aggressive behavior. This suggests
that a borderline group of grade I meningioma
which behaves aggressively and may have
recurrent or progressive disease. Therefore,
histopathological grading alone might not
correlate with the patient outcome. It is
important to distinguish WHO-grade I
meningiomas with aggressive behavior from
their non-aggressive counterparts.

9. Typical CT features
In 72%-85% of meningiomas, CT demonstrates
typical diagnostic features, including a sharply
circumscribed unilobular mass with a broad-
based dural attachment. On NCCT scans the
mass appears as an area of homogeneous
hyperattenuation “40-50 HU”. After the IV
administration of contrast material, the mass
homogeneously enhances.

12. Calcification:
Calcification is seen on CT in 20–27% of
meningiomas. It is usually microscopic or
punctuated, but may be large, conglomerate,
peripheral, or central. The presence of
calcification indicates slowly progressive benign
nature. Malignant meningiomas are rarely
calcified.

15. Hyperostosis
Another typical imaging characteristic of
meningioma is hyperostosis of the adjacent
calvarium in 18–50% of cases. It occurs only in
those masses that are immediately adjacent to the
bone.
Osteoma, fibrous displasia, Paget’s disease, and
hyperostosis frontalis may imitate the
hyperostosis typically seen in meningiomas.

18. Bone destruction by meningiomas is an
uncommon feature, found in approximately 3%
of cases. Benign as well as malignant
meningiomas may invade the skull. These
destructive meningiomas are typically associated
with adjacent areas of hyperostosis. If a purely
destructive skull lesion is identified, this is
more likely due to metastasis, sarcoma, or
myeloma.

22. Typical MRI features
Typically, meningiomas are peripheral
unilobular masses with broad-based dural
attachments and smooth, well-defined borders.
On T1W and T2W images, meningiomas are
usually isointense to normal gray matter (in
contrast with other intracranial tumors). Nearly
all meningiomas enhance rapidly and intensely
following IV contrast administration.

24. In general, T1WI offer little to no specificity
whereas T2W images can give information about
histological subtype, vascularity, and
consistency. Meningiomas hyperintense on
T2WI are usually soft, more vascular, and more
frequently of syncytial or angiomatous subtype.
Tumors hypointense or on T2WI tend to have
harder consistency and are more of fibroblastic
or transitional subtype.

27. White matter buckling
A useful feature in confirming the extra-axial
location of the suspected meningioma is the
inward bowing of the gray–white junction of the
adjacent brain parenchyma often called ‘white
matter buckling’.

29. Pseudocapsule
Another useful MR characteristic is the presence
of signal void pseudocapsule which consists of
linear signal void representing the dura itself,
interposed between the tumor and the brain
parenchyma, as well as of punctuate foci of
signal void owing to the displaced vessels. There
may also be a CSF cleft trapped between the
cortex and the meningioma.

32. Dural tail sign
A linear enhancement along the dura mater, on
either side of meningioma on contrast-enhanced
MRI. This sign is not specific to meningioma
and also observed in several conditions including
glioma, brain metastasis, acoustic neuroma and
lymphoma.

33. The triple criteria for DTS are: (1) Presence of at
least two consecutive sections through the tumor
at the same site in more than one imaging plane;
(2) Greatest thickness adjacent to the tumor and
tapering away from it; and (3) Enhancement
more intense than that of the tumor itself.

36. Atypical imaging features
Several imaging features such as peritumoral
edema, cystic changes, lipomatous
transformation, intracranial hemorrhage,
irregular contour, poorly defined margins, and
ring enhancement are considered unusual or
atypical.

37. Peritumoral edema (PTE).
About 60% of meningiomas are associated with
PTE. It is more common with large lesions but
may be extensive with small ones. Reports have
found that severe edema is associated with more
aggressive syncytial and angioblastic cell types,
and mild-to-moderate edema associated with
fibroblastic and transitional cell types.

39. Cystic meningioma
The term cystic meningioma has been used to
describe two different morphologies:
intratumoral cavities,
and extratumoral or arachnoid cysts.
The presence of neoplastic cyst should be
suspected when ring enhancement of the wall is
seen.

42. Lipoblastic meningioma
Lipoblastic meningioma represents a variant in
which there is a metaplastic change of
meningothelial cells into adipocytes. Lipomatous
meningiomas are markedly hypodense on CT
(negative HU) and may have minimal to slight
enhancement within the fatty regions.

44. Spontaneous intracranial hemorrhage
Spontaneous intracranial hemorrhage associated
with meningioma is an uncommon condition
with incidence 1.3% of all meningiomas The
most common type of bleeding is subarachnoid
hemorrhage, followed by intracerebral and
intratumoral hemorrhage.

47. Utility of advanced MRI techniques in the
diagnosis of meningioma
Advanced MR imaging techniques are usually of
little value in making the diagnosis in patients
with typical imaging findings of meningioma.
Atypical and malignant meningiomas tend to be
markedly hyperintense on diffusion-weighted
MR images and exhibit marked decrease in ADC
values when compared with normal brain
parenchyma.

53. MR spectroscopy may provide additional
information in differential diagnosis. The most
common finding in meningiomas is a high Cho
peak with low or absent NAA and Cr and
variable amounts of lactate. Most importantly, y
high ratio of Ala to Cr has been found in
meningiomas (relatively specific finding). MR
spectroscopy may differentiate histologically
atypical meningiomas on the basis of lactate
peak at 1.3 ppm.

58. Independent predictors
of non-grade I meningioma
Hyperintensity on DWI.
Disruption of arachnoid at brain-tumor
interface. PTE.
Heterogenicitiy on contrast enhanced MRI.
Irregular tumor shape.

60. En plaque meningioma
En plaque meningiomas is characterised by
diffuse and extensive dural involvement, usually
with extracranial extension into calvarium, orbit,
and soft tissues. Both CT and MR imaging are
useful to evaluate the extent of extradural and
calvarial involvement.

63. CPA meningiomas
CPA meningiomas represent the second most
common mass lesions of the CPA, although less
than 5% of all meningiomas occur in CPA.
Approximately, 80% of masses in the CPA are
acoustic schwannomas and half of the remainder
20% are meningiomas

65. Tuberculum sella meningioma
Tuberculum sella meningioma represent 3% to
10% of all meningiomas. They may be
associated with hyperostosis of the sphenoid
ridge and may be very invasive, spreading to the
dura of the frontal, temporal, orbital, and
sphenoidal regions. Medially, this tumor may
expand into the wall of the cavernous sinus,
anteriorly into the orbit, and laterally into the
temporal bone.

68. Orbital meningiomas
Orbital meningiomas account for less than 2% of
cranial meningiomas, but constitute 10% of all
intraorbital neoplasms, arising from the optic
nerve sheath between the globe and the optic
canal.

70. Intraventricular meningiomas
Intraventricular meningiomas are the most
common trigonal masses in an adult accounting
for approximately 2–5% of intracranial
meningiomas. About 80% are located in the
lateral ventricle, 15% in the third ventricle, and
about 5% within the fourth ventricle.

73. Subcortical meningiomas
Subcortical meningiomas are mainly deep
Sylvian meningiomas that arise from
leptomeningeal infolding in the Sylvian fissure
and involve branches of the MCA as they grow.
The mean age of appearance is reported to be
29.3 years, which is earlier than for ordinary
meningiomas. They are reported to be more
frequent in Japanese populations.

75. Differential diagnosis
There are multiple neoplastic and non-neoplastic
entities that clinically and radiographically
mimic meningiomas, including solitary fibrous
tumors, hemangiopericytoma, gliosarcoma,
leiomyosarcoma, dural metastases, Hodgkin’s
disease, plasmocytoma, Rosai Dorfman disease,
neurosarcoidosis, melanocytic neoplasms,
plasma cell granuloma, Tolosa-Hunt syndrome,
and pituitary macroadenoma.

76. The differential diagnosis of dural-based lesions
in the brain varies from incidental and benign to
symptomatic and malignant lesions. Careful
vigilance in patients with a history of cancer,
presenting with new symptoms or imaging
evidence of dural-based lesions, should raise the
possibility of dural metastasis.

78. Thank You.