AJR 2002; 178:768-769
© American Roentgen Ray Society
Atypical Meningioma Spreading via the Perivascular Spaces
Edmond Russ and
Mauricio Castillo
University of North Carolina School of Medicine Chapel Hill, NC
27599
Atypical meningiomas comprise about 4% of all meningiomas
[1] and show increased mitotic
activity, hypercellularity, large nuclei with prominent nucleoli, and
necrosis. According to the classification scheme proposed by the World Health
Organization [1], they are
grade II tumors. Their etiology is uncertain, but typical meningiomas may
undergo gene losses and gains, transforming them into atypical ones.
Radiation-induced meningiomas are also more likely to be atypical. Despite
gross total resection, approximately 29-40% of atypical meningiomas recur. We
present an atypical meningioma showing extension into the perivascular
spaces.
A 45-year-old man underwent partial resection of an atypical right frontal
meningioma. Two years later the patient developed an increasing visual deficit
and was evaluated on MR imaging. The study revealed a large and diffuse
dural-based plaquelike mass extending throughout both middle and anterior
cranial fossa and along the anterior falx cerebri (Fig.
1A,1B,1C).
Extension along the perivascular (Virchow-Robin) spaces at the level of the
right basal ganglia was present. Because of the extensive nature of the
disease, the patient decided to receive only supportive therapy.
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Fig. 1A. —45-year-old man with increasing visual deficit. Axial
(A), parasagittal (B), and coronal (C) enhanced
T1-weighted MR images show extensive enhancing meningioma involving middle
cranial fossae (right > left), anterior cranial fossae, cavernous sinuses,
and sella. Note brushlike (B and C) appearance of tumor as it
extends into perivascular spaces. On axial image (A), this extension is
seen as discreet rounded areas of tumor enhancement in right basal ganglia
region.
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Fig. 1B. —45-year-old man with increasing visual deficit. Axial
(A), parasagittal (B), and coronal (C) enhanced
T1-weighted MR images show extensive enhancing meningioma involving middle
cranial fossae (right > left), anterior cranial fossae, cavernous sinuses,
and sella. Note brushlike (B and C) appearance of tumor as it
extends into perivascular spaces. On axial image (A), this extension is
seen as discreet rounded areas of tumor enhancement in right basal ganglia
region.
|
|
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[as a PowerPoint slide]
|
Fig. 1C. —45-year-old man with increasing visual deficit. Axial
(A), parasagittal (B), and coronal (C) enhanced
T1-weighted MR images show extensive enhancing meningioma involving middle
cranial fossae (right > left), anterior cranial fossae, cavernous sinuses,
and sella. Note brushlike (B and C) appearance of tumor as it
extends into perivascular spaces. On axial image (A), this extension is
seen as discreet rounded areas of tumor enhancement in right basal ganglia
region.
|
|
Atypical meningiomas are more aggressive and invasive than typical
meningiomas. Atypical meningiomas may be plaquelike in configuration and
extend through the dura to the skull and scalp. The term
"meningiomatosis" refers to a completely different disorder.
Meningiomatosis is an entity in which a primary sarcoma (similar to a
fibrosarcoma) diffusely involves the meninges
[2]. In meningiomatosis, no
dominant mass is found. The imaging findings of this disease are nonspecific,
and the differential diagnosis includes diffuse meningioma, lymphoma,
leukemia, sarcoidosis, metastases, and primary meningeal gliomatosis (and
oliodendrogliomatosis). The perivascular spaces are cuffs of arachnoid
accompanying blood vessels entering or leaving the brain
[3]. These spaces are separated
from the brain parenchyma by the pia-glia that is considered the external
limiting membrane. The perivascular spaces thus contain subarachnoid space
(and cerebrospinal fluid), a central blood vessel, and the external limiting
membrane. As a blood vessel travels deeper, the pia, intima, and arachnoid
fuse and become one membrane without any potential space. At this level,
astrocytes surround the basement membrane of the capillary endothelium.
Although the function of the perivascular spaces is not certain, they allow
cerebrospinal fluid to travel into the brain and may play a role in its
absorption. The perivascular spaces may serve as a conduit for the spread of
infectious (particularly cryptococcus), inflammatory (sarcoid), and neoplastic
(glioblastoma multiforme metastases) processes. Although this is the first
case of a meningioma spreading into the perivascular spaces that we have
witnessed, this experience is not surprising because these tumors arise from
arachnoidal cells and tend to extend along meningeal surfaces. Atypical
meningiomas are also known to invade the brain, and perhaps it is via the
perivascular spaces that this invasion first occurs as seen on our
patient.
References
-
Kleihues P, Cavenee WK. WHO classification tumours of
the central nervous system. Lyons, France: IACR,
2000: 176-184
-
Burger PC, Scheithauer BW, Vogel FS. Surgical pathology
of the nervous system and its coverings, 3rd ed. New York:
Churchill Linvingston, 1991:176
-
Parent A. Carpenter's human neuroanatomy,
9th ed. Baltimore: Williams & Wilkinns, 1996:13
-14
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