They are the
most common benign tumors of the brain. Dural endothelioma,
fibroma, sarcoma, epithelioma, and fungoid tumors of the dura
are some of the older names that existed until Cushing
established the term meningioma in his Cavendish lecture of
1922. About 90 per cent of all CNS meningiomas are intracranial.
ranges around 20 per cent of all brain tumors. In India, the
incidence ranges from 9-15 per cent of all intracranial
neoplasms in various series. The incidence seems to be higher in
Africa, at 24-38 per cent. Meningiomas most commonly occur in
the middle decades of life. In India, these tumors have been
reported to occur predominantly between the third and the fifth
decades, with a peak in the fourth decade. Western literature
suggests maximum prevalence of meningiomas between the fourth
and the sixth decades. Meningiomas are more commonly encountered
in women than in men. There is no sex preference in older
incidence of meningiomas, usually multiple, is largely found in
association with central neurofibromatosis (NF-2).
are rare in children, they form 0.4-0.6 per cent of all
intracranial neoplasms in childhood. About two per cent of all
meningiomas occur in childhood and adolescence. Meningiomas in
children are more commonly malignant and often of the
haemangiopericytic and papillary type. A higher prevalence of
cystic meningiomas has also been reported in children. The other
distinctive features of meningiomas in children are i) no sex
preference, ii) a particularly high incidence of
intraventricular tumors, and iii) significant association with
origin of a meningioma, like of any other neoplasm, is
uncertain, some antecedent factors have been implicated in the
initiation and growth of meningiomas.
head has been blamed for a long time as an important
contributory cause. Though in the majority there are no
morphological signs of trauma at the site of the tumor, in some
cases the tumor had arisen under a fracture, from an area of
dural scarring or even from a retained foreign body
intracranially. Despite these conflicting reports, there is
enough evidence to suggest that at least some cases of
intracranial meningiomas are initiated by head injury.
from an ossified subdural hematoma or tubercular pachymeningitis,
was incriminated in the past as a causative factor. However, it
is not considered relevant. Papova virus large T-antigens have
been demonstrated in a high percentrage of meningiomas. Herpes
virus large T- antigens seem to induce meningioma growth.
Recent technical developments have allowed the identification of
small pieces of viral proteins in human tumors, including
meningiomas. Although it is not possible to say whether these
viral genes or vital proteins are the etiological gents in
meningiomas, their presence is an important step in establishing
a relationship between the virus and meningioma.
induced meningiomas have appeared following high dose
irradiation for intracranial growths and low dose radiation to
the scalp for fungal disease and occasionally, for a vascular
nevus. The onset of tumor formation can be 12-27 years later.
While the majority of the radiation induced tumors following
high doses were thought to be sarcomas, a recent review of the
world literature suggested, radiation induced meningiomas are at
least five times more numerous than gliomas or sarcomas. Some of
the unique features of radiation induced meningiomas are 1)The
neoplasm lies below and often invades the atrophic scalp with
alopecia, 2)The tumor occurs in a much younger age group; the
greater the radiation dose, the shorter the latency and the
younger the patient’s age at presentation, 3) No female
predominance, 4) A calvarial location abutting against the
sagittal sinus, 5) Multiple tumors are more common (25-29 per
cent), 6) Recurrence following excision is common.
carcinogenic effect of thorium dioxide has been blamed in the
genesis of some meningiomas.
Chromosomal abnormalities in meningiomas are now well
established and probably more consistently seen than in any
other tumor except chronic granulocytic leukemia. In
approximately 80 per cent of the tumors analyzed there is a loss
of heterozygosity on at least one chromosome 22 DNA marker. The
frequency and consistency with which monosomy 22 appear has led
to the postulation of a uniform pathogenetic mechanism and it
has been hypothesized that with the loss of genetic material on
chromosome 22, a previously suppressed oncogene is probably
unmasked. The role of SV-40 virus in meningiomas is disputed by
incidence of meningiomas, usually multiple, are associated with
neurofibromatosis 1 & 2. Patients with von Recklinghausen’s
disease develop meningiomas at an early age; 19-24 per cent of
adolescents with meningiomas have neurofibromatosis. The other
evidence of heredofamilial occurrence is the association of
meningioma with Von Hippel-Lindau disease.
association is indicated by the greater incidence of meningiomas
in females, its increase in size related to pregnancy and the
luteal phase of the menstrual cycle, and the documented
association between meningioma and breast carcinoma in the same
patient. However, the existence of sex-specific hormone
receptors in meningiomas has long been a controversial issue.
frequent inconsistencies, binding assay techniques in
meningiomas suggest: (1) high levels of progesterone receptors,
(2) moderate concentration of androgen receptors, and (3) an
equivocal report about the status of estrogen receptors. The
recent cloning of complementary deoxyribonucleic acid (cDNA),
encoding human estrogen, progesterone and androgen receptors has
facilitated the direct investigation of hormone receptor gene
expression without the limitation of variations in binding assay
interpretation. The coexpression of androgen and progesterone
receptor messenger ribonucleic acid (mRNA) and protein product
have been reported in few meningioma. Estrogen receptors in
mRNA expression were not detected.
meningiomas are intradural. However, extradural meningiomas,
both cranial and spinal, have been reported. Meningiomas may be
globular in form or flat.
globular tumors may be rounded, ovoid or lobulated and
usually have a relatively small dural attachment. Globular
tumors are usually smoothly lobulated and well encapsulated
with the result that
characteristically, the adjacent brain is not invaded and an
intact pial covering is usually present.
contrary, the flat tumors commonly referred to as meningioma
en-plaque, are less well encapsulated with a tendency to
involve the pia as well as the overlying bony structures.
They are attached over a relatively broad area of the dura.
Meningiomas have a tendency to invade the dura and its
venous sinuses and may grow through the skull into
meningioma (H&E): meningothelial cells
and fibrous areas with attempts at whorl formation
(doublearrow) and psammoma
A majority of
the tumors are solid, but areas of cystic degeneration or a
predominantly cystic tumor may occur. Granular or patchy
calcification may occur, especially in the psammomatous variety
and occasionally, the tumor may be totally calcified.
Peritumoral brain edema is a common feature and suggests an
meningiomas are more commonly encountered in the pediatric
population (11 per cent), in the elderly (up to 20 per cent) and
in patients with neurofibromatosis (20 per cent). These tumors
can occur at any location within the cranium, and the
association of cranial and spinal meningioma is rare.
Multiplicity may result from a multicentric origin of the tumor
or from dissemination of tumor cells by CSF during surgery.
association with aneurysms and AVMs and gliomas has been
reported and considered coincidental.
with other intracranial neoplasms, such as acoustic neurinoma,
in the absence of neurofibromatosis, is extremely rare.
changes may, occasionally occur at the periphery of a meningioma
(peritumoral) or inside the tumor (intra-tumoral). Intratumoral
cysts arise from degeneration, hemorrhage or necrosis.
Peritumoral cysts arise from adhesions and accumulation of
protein containing CSF, reactive gliosis, fibroblastic
proliferation in the final stage of peritumoral oedema or rarely
as an exudate from the tumor surface. From a surgical point of
view, peritumoral cystic meningiomas present greater
difficulties and unless every effort is made to excise not only
the mural nodule, but also the cyst wall with the help of an
operating microscope, recurrence is likely to occur. The cystic
variety is more commonly encountered in males, in children and
in the supratentorial compartment. Cystic changes in a
meningioma may have a serious connotation as eight per cent of
cystic meningiomas are reported to be malignant and 12 per cent
are reported to be angioblastic, probably hemangiopericytic.
arise from the arachnoid cells. The arachnoid cell has a
polyblastic character and is functionally multipotential. This
results in different histological and cytological variations of
Classification of the meningiomas has been changed several
classification of meningioma (2000):
Meningothelial (grade I)
uniform polygonal cells with indistinct cytoplasmic borders
arranged in sheaths or medium size globules.
Fibroblastic (grade I)
shaped cells in a dense collagen matrix.
Transitional (grade I)
Psammomatous (grade I)
more elongated and separated . Form whorls which by
degeneration forms Pssmmonian bodies (concentric laminas of
degenerated cells have a concentration of calcium salts).
Angiomatous (grade I)
sclerosing blood vessels.
Microcystic (grade I)
stellate and vacuolated cytoplasm with long cytoplasmic
differentiation of meningothelial cells resulting in the
production of hyaline inclusions.
Lymphoplasmacyte-rich (grade I)
Lymphoplasmacytic infiltration in the meningothelial
component of the tumor.
cells with differentian into spindle cells.
Mixture of clear cells and meningothelial cells.
Spindle or epitheloid cells disposed in
chordoma-like clusters and cords in a myxoid matrix.
More cellularity and cytologic atypia than grade I tumors.
pattern with few anaplastic features.
Abundant eosinophilic cytoplasm resembling rhabdoid tumor.
Anaplastic (grade III)
high cellularity, brain invasion, frequent mitosis, invasion
of the blood vessels and necrosis.
meningotheliomatous meningioma is the commonest histological
type, though some report them to be less common. Recent
advances in pathology include the recognition of cystic
types, evaluation of proliterative activity and the use of
markers in the evaluation of the aggressiveness of
meningiomas in the delineation of malignant phenotypes.
Approximately 90 per cent of the intracranial meningiomas
are supratentorial. In the cranial cavity as a whole, the
anterior half is involved far more frequently than the
common sites are the convexity, parasagittal, falx, and
sphenoid ridge, together making up 60 per cent of
from the arachnoid villi of the superior sagittal sinus and
often involve the adjacent convexity dura and falx. Nearly
50 per cent invade the sinus, 50 per cent get secondary
attachment to the falx and 25 per cent are bilateral.
Hyperostosis is associated with 25 per cent of these tumors
and is a valuable pointer to their diagnosis.
Falcine meningioma arises from the falx cerebri or
inferior sagittal sinus and may rarely invade the superior
sagittal sinus. It is usually completely concealed by the
overlying cerebral cortex and does not cause bony changes.
About 50 per cent of the tumors grow through the falx to
become bilateral. Falx meningiomas are about five to seven
times less common than parasagittal meningiomas.
Cerebello pontine angle
distribution of parasagittal and falx meningiomas along the
longitudinal axis is about 20, 50 and 30 per cent in the
anterior, middle and posterior third, respectively.
anywhere over the convexity of the cerebrum. Convexity tumors
may cause erosion of the overlying skull and may come to lie
under the scalp.
may arise from the anterior part near the crista galli, from
near the cribriform plate or the planum sphenoidale. These
tumors can be silent for a long time. Growing posteriorly,
these tumors compress the optic nerve and chiasma leading to
unilateral blindness or bitemporal hemianopia with optic
atrophy. With the rise in intracranial pressure, there may be
papilledema in the opposite eye and Foster Kennedy syndrome may
be seen. Further extension posteriorly puts pressure on the
hypothalamus and pituitary gland. By this time, the ICP rises to
cause obvious features of raised ICP. It is not unusual, even
today, to see large olfactory groove meningiomas presenting with
blindness and raised ICP. Rarely, by eroding through the
orbital roof or the cribriform plate, the tumor may cause
meningiomas arising from the tuberculum sellae, planum
sphenoidale, diaphragma sellae and/or anterior clinoid process
in close proximity to the optic chiasma, displacing it
posteriorly and superiorly and stretching it. They may extend
into the orbit, paranasal sinuses, cavernous sinus, sella,
infratemporal fossa, and posterior fossa.
Sphenoid Wing (clinoidal) Meningioma
can be divided into two general categories. These are: 1)
globular and 2) diffuse or enplaque. The globular meningioma
grows en mass from the anterior clinoid and medial sphenoid,
involves the ICA and MCA to variable degrees and displaces or
engulfs the optic nerves, chiasma, and optic tracts and
compresses the adjacent frontal and temporal lobes. The second
variety grows diffusely from a similar area with involvement of
the cavernous sinus and often without symptoms of an
intracranial mass. As they grow bigger, the branches of the
fifth, fourth and sixth cranial nerves may be affected.
Sphenoidal Wing (Alar) Meningiomas
arise from the middle third of the sphenoid wing in relation to
the superior orbital fissure (SOF) and the anterior portion of
the middle cranial fossa (MCF). Growing posteriorly, it indents
the temporal lobe.
Sphenoidal Wing (Pterional) Meningiomas
with a minimal reaction in the sphenoid ridge is more common
than the en plaque variety. The tumor occupies the
middle cranial fossa, may extend into the anterior fossa and
attain a large size before symptoms become obvious.
Meningioma en plaque, is uncommon and behaves in a peculial
fashion, in that the tumor spreads along the meninges as a
plaque causing an intense bony reaction. There is hyperostosis
of the pterion as well as the lateral half of the lesser wing of
the sphenoid. Tumor may also be present in the lateral and
posterior orbit and may involve the optic canal.
classified into (a) the confined and (b) the extensive group.
The confined tumors are small tumors that involve the cavernous
sinus and Meckel’s cave, the middle fossa or the sella turcica.
The extensive tumors include petroclival, medial sphenoid wing
and infratemporal tumors that involve the cavernous sinus. These
are generally known to be slow growing tumors, though the
natural history is not clear.
Cranial Fossa Meningiomas
anywhere in the middle cranial fossa or may extend into it from
the anterior surface of the petrous temporal bone or lateral
surface of the cavernous sinus. Paresthesia or numbness of the
face may be present and lacrymation may be impaired. The tumor
indents the undersurface of the temporal lobe and may remain
asymptomatic for a long time. The foramen spinosum and the
middle meningeal artery are considerably enlarged.
8-12 per cent of all intracranial meningiomas and 7-12 percent
of all posterior fossa tumors. They are, conventionally,
classified according to the site of dural attachment as follows:
1) cerebellar convexity, 2) tentorium, 3) posterior surface of
the petrous bone, 4) clivus, 5) foramen magnum, and 6) fourth
ventricular (tela choroidea. The posterior surface of the
petrous bone is the commonest site of attachment (42 per cent)
in posterior fossa meningiomas and these meningiomas constitute
6-8 per cent of all cerebellopontine angle tumors. The other
characteristic features of these tumors are a broad base towards
the petrous bone and associated hyperostosis or erosion of the
arising from the clivus are attached at any of the several sites
along the petroclival borderline where the sphenoid, petrous,
and clival bones meet. The zone of adherence to the dura is
commonly wide and overlaps two or more of these sites.
Moreover, almost all these tumors have wide tentorial
occupation. Foramen magnum meningiomas are the commonest tumors
of the foramen magnum.
from any location on the tentorium and account for two to three
per cent of all intracranial meningiomas. Tentotial meningiomas
may grow upwards into the posterior fossa or in both
directions. Nearly 20 per cent have significant supra and
meningiomas have, as part of their dural base, the dura forming
the torcular, i.e., they arise from, invade, or are attached to
a wall of the torcular itself. These tumors represent about one
per cent of intracranial meningiomas. True torcular meningiomas
are usually bilateral, based on the torcular. When there is
only unilateral extension from the torcular it is usually a
lateral tentorial meningioma which has got secondary attachment
to the torcular. Often, these tumors have both infra and
supratentorial extension bilaterally.
1-1.7 percent of intracranial meningioma and usually arise from
the choroids plexus of the lateral ventricle, but may occur
rarely in the third or fourth ventricle. The lesion is more
frequent in the left lateral ventricle in middle aged women, but
has been well documented in children. 60-94 per cent of the
lateral ventricular meningiomas arise from the choroid plexus at
the trigone. Intraventricular meningiomas are thought to arise
from arachnoid tissue, which is carried with the choroid plexus
as the ventricular system invaginates.
are rare. The usual sites are near the jugular foramen, the
internal auditory meatus, the region of the geniculate ganglion
and the sulci of the superficial petrosal nerves. Jugular
foramen meningiomas are often clinically indistinguishable from
glomus jugulare tumors. Occurring inside the temporal bone,
these tumors often infiltrate the surrounding bone. Some of
these cases have en plaque tumors over the petrous.
ExtracraniaL (excluding spinal) meningiomas constitute one per
cent of all meningiomas and can be classified into four groups.
These are as follows:
Arising from intracranial dura and extending extracranially.
This is the most common type of extracranial meningioma.
Extracranial extension of intracranial meningiomas is described
in four principal sites: 1) the orbit (7.5 per cent), 2) the
outer dipole and scalp (six per cent), 3) the upper respiratory
tract (2.5 per cent) and 4) the parotid region and infratemporal
fossa (1.25 per cent). Most parapharyngeal meningiomas are
related to the cranial nerves, particularly 7th, 9th,
10th, 11th and 12th.
Head and neck extracalvarial meningiomas: Extracranial
meningioma, in the absence of an intracranial mass, but
associated with hyperostosis of the underlying skull, osteolytic
changes and intra-osseous tumor infiltration have been described
in the outer surface of the frontal, temporal and parietal
bones. A primary intra-osseous location without underlying
dural involvement is very rare. Arachnoidal cell clusters
normally found at the level of the internal auditory meatus(IAM),
jugular foramen, geniculate ganglion, roof of the eustachian
tube or in association with the greater or lesser petrosal
nerves, may represent the cells of origin of temporal bone
Ectopic meningiomas not associated with the craniospinal
meninges: An ectopic meningioma was first reported by Winkler,
who, in 1904, described a case of paravertebral subcutaneous
meningioma in a 10 year old girl. Other ectopic sites reported
are the glabella, pterygopalatine fossa, intraoral, nasal
cavity, paranasal sinuses, parotid gland, neck, cutaneous areas
of the scalp, the face, mediastinum, lung, little finger,
brachial plexus, lung, and adrenal gland
Metastatic meningiomas: Metastases from a meningioma could be
extraneural or through the CSF pathways. A total of 16 cases
with CSF spread have been reported. Eleven cases had features
of malignancy in the original neoplasm and seven cases had
associated extraneural metastases. In five cases both the
original tumor and the deposits preserved their benign
character. Though tumor seeding at operation might have been
the explanation in two, no surgery was performed in three and
these are examples of spontaneous leptomeningeal metastases.
is more frequent than CSF dissemination. The hemangiopericytic
and papillary variant had a greater propensity to metastasize.
Seventy per cent of patients recorded to have had a
metastasizing meningioma have been subjected to previous
craniotomy. However, spontaneous hematogenous metastases have
been reported and have been attributed to invasion of the
superior sagittal sinus, cavernous sinus and its perineural
lymphatics. Nearly one-third of all the metastases were
observed in the lung and the other common metastatic sites were
liver (19 per cent), lymph node (12 per cent) and bone (nine per
cent). The rare sites reported are the mediastinum, kidney,
thyroid and parotid.
presentation of a meningioma is classically with seizures,
hemiparesis, visual field loss, aphasia or other focal
symptoms. The clinical presentation depends on the location of
the meningioma. Most meningiomas are slowly growing lesions and
symptoms and signs will frequently develop very slowly. Finally
an increasing number of meningiomas are asymptomatic and are
They may exist for a long time without symptoms or they may lead
to early irritation of the cerebral cortex, resulting in partial
or generalized epilepsy, especially if located adjacent to the
central sulcus. The tumor makes a bed for itself on the surface
of the brain.
and falx meningiomas:
Anterior-third meningiomas, located between the crista galli and
the coronal suture, have a more insidious onset and often attain
a large size before diagnosis. Headache is the predominant
symptom and may be present for years followed by gradually
progressive impairment of memory, intelligence and personality
changes. Generalized epilepsy is a presinting symptom in 25-50
per cent of patients. Ataxia, tremor and ipsilateral facial
pain may, occasionally, accompany a large meningioma in this
location and thus may be misdiagnosed a posterior fossa tumor.
Tumors in the middle-third, from the coronal suture to the
lamboid suture, classically present with contralateral focal
motor sensory epilepsy followed by progressive weakness of the
lower limb. These tumors are detected at an early stage because
of focal epilepsy. Bilateral tumors may, occasionally, give
rise to bilateral disturbances and rarely paraplegia which may
be wrongly attributed to spinal pathology. Tumors in the
posterior-third, between the lamboid suture and the torcular
Herophili, may present with features of raised ICP alone. The
only characteristic sign, a homonymous field defect, either
quadrantanopic or hemianopic, may not be noticed by the
patient. Epilepsy is uncommon.
Headache is the most common presenting symptom. Though anosmia
occurs in 85-90 per cent of cases, it is rarely the initial or
presenting symptom. As these tumors grow in size, symptoms of
pressure on the frontal lobe may be apparent. Mental symptoms
often lead the patient to seek treatment from a psychiatrist.
While inferior tumors may cause excitement or restlessness,
pressure over the convexity of the frontal lobe may lead to
indifference and apathy. The more anterior tumors cause a
central scotoma and papilledema. Growing posteriorly, these
tumors press on the optic nerve and chiasma leading to
unilateral blindness or bitemporal hemianopia with optic
atrophy. With the rise in intracranial pressure, there may be
papilledema in the opposite eye and Foster Kennedy syndrome may
be seen. Further extension posteriorly puts pressure on the
hypothalamus and pituitary gland. By this time, the ICP rises
to cause obvious features of raised ICP. It is not unusual,
even today, to see large olfactory groove meningiomas presenting
with blindness and raised ICP. Rarely, by eroding through the
orbital roof or the cribriform plate, the tumor may cause
Meningiomas arising from the tuberculum sellae, planum
sphenoidale, diaphragma sellae and/or anterior clinoid process
are conventionally grouped under suprasellar meningiomas. As
these tumors arise in close proximity to the optic chiasma,
displacing it posteriorly and superiorly and stretching it,
visual symptoms are early and common, leading to earlier
detection than olfactory groove meningiomas. Ninety to ninety
nine percent of the patients complain of either monocular (55
per cent) or binocular (45 per cent) visual loss. The other
common symptoms are headache, epilepsy and mental changes. The
presence of bitemporal hemianopic field defects in the presence
of a normal sized sella should suggest the possibility of a
suprasellar meningioma. However, in the early stages vision may
be affected in only one eye. Pituitary hypofunction is uncommon
and is found in only 4-13 per cent of these patients.
sphenoid wing meningiomas:
They present with slowly progressive ipsilateral visual
impairment with or without diplopia. Diplopia secondary to
oculomotor paresis is more common in the diffuse variety. As
they grow bigger, the branches of the fifth, fourth and sixth
cranial nerves may be affected. There may be proptosis because
of either obstruction of the anterior end of the cavernous sinus
or draining orbital veins. The other presenting symptoms may be
headache, epilepsy or psychiatric disturbances. Pressure on the
hypothalamus may become apparent as the tumor grows upwards and
Sphenoidal Wing (Alar) Meningiomas:
Proptosis is a frequent early symptom. The tumor usually attains
a large size before it is diagnosed. Growing posteriorly, it
indents the temporal lobe and thus uncinate fits or other
symptoms of complex partial epilepsy may become manifest.
Sphenoidal Wing (Pterional) Meningiomas:
with a very slowly progressive unilateral, painless, non-pulsatile
proptosis and fullness under the temporalis muscle. Some
patients complain of a dull pain over the temple and mild local
generally known to be slow growing tumors, though the natural
history is not clear. The symptoms are of long duration and
include retro-ocular pain, mild exophthalmos and double vision
due toe VI nerve involvement. Anesthesia in the distribution of
the first division of the V nerve may be seen. The confined
tumors generally cause more symptoms than the extensive tumors.
Cranial Fossa Meningiomas:
Paresthesia or numbness of the face may be present and
lacrymation may be impaired. The tumor indents the undersurface
of the temporal lobe and may remain asymptomatic for a long
Depending on the site of origin, the tumor causes cerebellar,
cerebellopontine angle or brainstem syndromes with multiple
cranial nerve palsies. Features of raised ICP appear earlier
than in supratentorial meningiomas.
They present with otological problems; symptoms of ear
discharge, mastoiditis, polyps or granulation tissue. Hearing
impairment and facial nerve paresis often develop. These
patients invariable have some degree of lower cranial nerve
paresis. It is not uncommon for these patients to present with
a submandibular swelling or a swelling in the posterior
pharyngeal wall. When the lesion extends into the posterior
fossa, cerebellar signs may become prominent.
usually present with symptoms of increased ICP; frontal lobe
signs may be present.
in meningiomas has been more frequently reported in tumors with
a parasagittal or convexity location, and more often in the
malignant or angioblastic varieties. However, an apoplectic
presentation is much less common. Other reported intracranial
vascular events related to meningiomas are rare and are
secondary to either dural venous sinus occlusion manifesting as
pesudotumor cerebri or arterial occlusion.
Abnormalities in the skull films of patients with
intracranial meningiomas have been variously reported as
36-77.5 per cent in the literature. Relatively less vascular
meningiomas may cause a deposit of minerals in the bone,
leading to an increased.
and thickening or hyperostosis, the commonest primary
change. Sclerosis of the bone does not necessarily represent
bone invasion, however, sclerosis of the outer table of the
skull as well as spiculation of the bone suggest penetration
of the bone by the tumor. Hyperostosis may be focal near
the attachment of the tumor to the meninges, the bony
projection resembling a osteoma. In other cases there is a
diffuse thickening of the bone. This process is particularly
well marked in the region of the sphenoid wing. Hyperostosis
is reported in 15-44 per cent of adults and 10 per cent of
children with meningiomas.
vascular tumor nears the skull causes rarefaction and bone
absorption. Lytic skull defects suggest penetration of the
bone by the tumor and occasionally, the tumor may protrude
through a defect in the skull and lie under the scalp.
Meningiomas associated with a lytic destructive reaction are
reported to be biologically more aggressive and are more
likely to recur. Osteolytic changes are seen in 12 per cent
of adults and nine per cent of children with meningiomas.
vascular markings are reported in 4-20 per cent of adults
and four per cent of children: these could be either focal
areas of increased vascularity at the tumor attachment
producing a sinusoidal appearance in the bone, or an
enlargement and tortuosity of meningeal vascular channels.
Asymmetric unilateral enlargement of meningeal vascular
channels and an ipsilateral dilated foramen spinosum are
highly suggestive of a meningioma.
calcification has been reported in 9-20 per cent of adults
and 13 per cent of children. Psammoma bodies, stromal
calcification and rarely, tumor ossification result in
It is the
imaging of choice. On the unenhanced MR meningiomas are
often isointense with brain on T1 and T2 weighted images.
Extra-axial mass effect suggested by white matter buckling,
a rim of CSF around the mass, a pial vascular rim and a
shorter T2 of the mass are described as characteristics of
meningioma. Gadolinium enhanced MR suggest that MR is
better suited for identifying the extra-axial location of
the tumor, the broad contact with the meninges, the tumor
capsule and meningeal contrast enhancement adjacent to the
tumor, i.e., the meningeal sign. CT is, however, superior
in demonstrating calcification and atypical tumor density.
Both methods provided nearly equal results in demonstrating
mass effect, hyperostosis and contrast enhancement.
Contrast enhanced MR (CEMRI) is particularly superior in the
diagnosis of meningiomas of the skull base, posterior fossa
and high convexity.
thickened and enhanced dura, variously called ‘dural tails’
and ‘the meningeal sign’ can be identified adjacent to some
meningiomas. Dural tails are considered as signs of tumor
infiltration along the dura, as proven by histopathological
examination. Incomplete excision of this extensive dural
tail may lead to recurrence.
spectroscopy may also be used for metabolic or
functional studies of meningiomas.
contrast enhanced (CE) CT scans are positive in 96 per cent
and diagnostic of a meningioma in 90 per cent of cases.
Meningiomas are dura based extra-axial mass lesions with
broad contact with the meninges. On the plain CT 75 per cent
of tumors are hyperdense and 14.4 per cent are isodense.
They are often multi-lobulated and smooth in contour,
adjacent to dural structures and may be calcified in some
areas. Intravenous X-ray contrast enhances meningiomas
uniformly and brightly. In about 15% of cases atypical
patterns such as, necrosis, cyst formation or hemorrhage is
found. Indistinct margins, marked edema, mushroom like
projection from the tumor, invasion deeply into the brain,
and heterogeneous enhancement all suggest aggressive types.
Peritumoral brain edema is seen in 60-75 per cent of
meningiomas. The edema around the tumor is associated with
aggressive tumors, and is either a result of a break down of
the blood-brain barrier or a secretion of the tumor itself.
The association of bone changes like hyperostosis or a lytic
area at the tumor base helps in the diagnosis of meningiomas.
Peritumoral low attenuation may also be caused by
demyelination, entrapped ventricular CSF, a subarachnoid
cyst or peritumoural cyst, or the co-existence of a glioma.
angiography and MR angiography
delineates the encasement and displacement of the
intracranial vessels and is as good as angiography.
The availability of CT and MR has considerably decreased the
indications for angiography in the diagnosis of brain
tumors. Still, angiography is often preferred by the
surgeons in the management of parasagittal, falx and basal
meningiomas and also to study the encasement of major
intracranial arteries, the patency of the dural sinuses and
the venous anatomy (e.g. cortical venous drainage to the
sagittal sinus in parasagittal or falx meningiomas and the
anatomy of the vein of Labbe in petroclival meningiomas),
for planning the operative approach. Occasionally,
angiography may be helpful in the diagnosis of a meningioma
in an atypical case, by demonstrating external carotid
supply to the tumor, although other primary tumors of the
meninges and metastatic tumors of the calvarium may also
have an external carotid supply. Currently angiography is
more often used in the evaluation of the feasibility of
(PET) with F-2-fluorode-oxyglucose has been used to evaluate
small changes in CT or MR imaging to determine whether these
were recurrent tumours. Research in meningioma receptor
ligands for PET scans may reveal additional information of
the tumor biology useful for the preoperative assessment.
objective of surgery is total removal of the meningioma,
including the dural attachment and bone that is involved by
the tumor. The completeness of surgical removal is the
single most important prognostic factor. However, when total
removal entails unacceptable risks of morbidity or
mortality, it is prudent to be satisfied with subtotal
excision. Sound judgment in choosing the best treatment
depends on a high level of clinical acumen, for the best
treatment is that which is best for the patient, not
necessarily what is best for the tumor. The factors having
a direct bearing on the surgery of meningiomas are its
location, vascularity, size and consistency.
embolization in the external carotid system, though helpful
in reducing bleeding and shortening the operation time; is
not without the hazard of inadvertent reflux of emboli into
the internal carotid system causing cerebral infarction.
Surgery should follow within 24 hours of embolization. As an
alternative, I prefer to expose the carotids at the neck for
temporary occlusion in highly vascular lesions.
Preoperatively, all patients are prophylactically put on
anticonvulsants. I prefer to give intravenous dexamethosone
(0.5 mg/kg body weight stat followed by 4mg 6 hourly) the
day before the surgery along with H2 antagonist.
the head is secured higher than the level of the heart and
without compression of the neck veins.
As a general
rule, the site of incision is positioned as the highest area in
the scalp to maximize the accessibility of the tumor. Free bone
flaps are generally preferred over the osteoplastic flap.
Hyperostosis and infiltration of bone by the tumor increases the
difficulty during elevation of the flap. Bleeding from the bone
can be most troublesome as the saw cut is being made and also
when the bone flap is being elevated. Vigorous and frequent
application of bone wax and rapid turning of the flap help to
a layer of arachnoid usually separates the meningiomas from the
brain, cranial nerves, and blood vessels. By accessing and
staying within this surgical plane, the chances of neural and
vascular injury are minimized. Early extensive debulking, helps
in definition of the archnoidal plane. Operative microscope
is mandatory to stay within the archnoidal plane. The best
way to free the adherent arteries is to begin the dissection at
uninvolved segments of the vessels.
tumor is excised, the involved dura and the bone are excised as
well and duraplasty with pericranium or temporalis fascia is
carried out. Unresectable dura should be aggressively cauterised.
Calvarial cranioplasty is better deferred as a later procedure
to accommodate post operative edema.
Considerations by tumor location:
offer the greatest potential for total tumor removal with a wide
dural margin. A circumferential dural incision around the tumor
insertion allows for early devascularization in the tumor.
Central debulking helps in accessing the arachnoidal plane.
Parasagittal and Falcine meningiomas, their proximity
to, and the extent of involvement to the sagittal sinus and the
draining cerebral veins must be considered. Tumor invasion
anterior to coronal suture may be managed with sinus ligation
and excision. Excision of patent sagittal sinus, posterior to
coronal suture carries significant risk of morbidity and
mortality. Tumors attached to the lateral wall, without
significant infiltration into the sinus lumen, can be managed by
dissecting the tumor off the sinus and achieving hemostasis by a
combination of coagulation and pressure over surgicel and
gelfoam. If the tumor has infiltrated the sinus lumen in the
lateral aspect only, it may be excised and the sinus
progressively closed with a continuous running suture. Excision
of the sinus followed by repair with autogenous venous grafts is
being increasingly practiced. It is prudent to perform a near
total tumor resection, leaving the involved sinus undisturbed.
Utmost care is taken when dissecting at depth to avoid injury to
anterior cerebral arteries. Every effort should be made to
preserve large cortical veins. Extensive tumor debulking avoids
excessive brain retraction. Inferior sagital sinus is usually
involved in falcine meningiomas and may be excised.
anterior and middle skull base tumors may extend to several
intra and extracranial compartments. Orbital and/or
osteotomies and other more
extensive skull base approaches may be needed to allow a
more basal approach to minimize brain retraction, and also help
clear the involved bone and the dura of the skull base.
Continuous CSF drainage though a lumbar catheter may obviate the
need for brain retraction.
displace the optic chiasm back and the optic nerves laterally
and superiorly; carotid artery may be found medial to the
displaced optic nerve. The pituitary stalk is posterior to the
tumor along the membrane of Lilliequist, which separates the
tumor from the neurovascular structures of the posterior fossa.
Optic deroofing may be required to remove tumor extension.
Olfactory Groove Meningiomas arise more anteriorly, and push
the optic chiasm and optic nerves dowm. Large tumors may require
a midline a bilateral bone flap. The anterior end of the
sagittal sinus may be ligated and the falx cerebri detached from
its inferior attachment when indicated. Any extension of the
tumor into the air sinuses can be removed by a
approach or a combined
Meticulous repair of the anterior cranial fossa is necessary to
prevent CSF rhinorrhoea. The approach may be modified for other
suprasellar meningiomas. They may derive blood supply from the
branches of the anterior cerebral artery and anterior
communicating complex. They must be traced to the tumor prior to
excision of medial sphenoid wing meningiomas, especially
those with significant involvement of the cavernous sinus,
though not impossible, is usually associated with significant
morbidity. Moreover, whether the patient really experiences
long term benefits from more extensive surgery and the increased
risk of surgery, or, whether partial removal of the tumor
followed by radiotherapy is better, is still debated. The ICA
and its branches, as well as the optic, oculomotor, and
olfactory nerves are at risk. The ophthalmic artery crosses the
anterior corner of the opticocarotid triangle, and its location
must be anticipated. The anterior clinoid meningiomas usually
extend into cavernous sinus. Attempts at radical excision of the
tumor in the SOF usually results in ophthalmoplegia. Hence, a
more conservative alternative is excision of the intracranial
mass followed by radiosurgery or periodic observation.
are usually easily achieved with careful microdissection of the
branches of the MCA. The uncommon, meningioma en plaque,
is approached through a frontotemporal extradural route. The
hyperostotic posterolateral wall of the orbit needs to be
drilled out exposing the periorbita and frontotemporal dura.
Bone above and below the superior orbital fissure, over the
optic canal, anterior clinoid process, roof of the orbit and
floor of the middle cranial fossa may also need to be removed
depending on the extent of the lesion. Dural excision and
intradural tumor removal completes the surgical exercise.
Careful reconstruction of the dural and bone defect is
essential. This extensive surgery should be contemplated with
utmost caution, as it is rarely possible to completely eradicate
the tumor and moreover, some patients may develop visual
deterioration following surgery.
regarding surgery in Cavernous Sinus Meningiomas depends
on the age and general condition of the patient and whether
relief from symptoms can be provided by operative treatment.
Recent advances in microsurgical
skull base techniques
have made total excision of these tumors invading the cavernous
sinus feasible with reconstruction of the internal carotid
artery by a bypass graft.
can be approached by various routes depending on their
disposition in the longitudinal axis. An anteriorly located
tumor can be managed by either a frontotemporal approach,
extended anterior temporal approach with an anterior temporal
lobectomy or by a subtemporal approach. In large tumours, it
may be better to sacrifice a part of the inferior temporal gyrus,
to avoid excessive retraction and contusion of the temporal lobe
while employing the subtemporal approach. The vein of Labbe
should be protected at all costs to prevent temporal lobe
infarction. For more posterior medial tentorial tumors,
subtemporal approach is preferred.
meningiomas are best approached by the occipital transtentorial
route. An alternative approach is the supracerebellar route
popularised. Torcular meningiomas are approached by either a
supra or infratentorial approach or a combined approach
depending on the extent of the tumor. Almost always a bilateral
approach is necessary. Unless the torcular Herophili is
occluded completely and adequate collaterals have developed,
only subtotal excision is advisable. Focal external cobalt beam
irradiation of the residual tumor is recommended in such an
lateral tentorial meningiomas are approached either by a
subtemporal, occipital, or temporoparietal route depending on
the dominant extension of the tumor. The main limiting factor
for excision of the posterolateral tumor is involvement of the
transverse and sigmoid sinuses. The main limiting factor for
excision of the posterolateral tumor is involvement of the
transverse and sigmoid sinuses. Total excision with ligation of
the sinus is indicated only in the presence of good torcular
anastomosis and a patent contralateral transverse sinus. In
tumors with both supra and infratentorial extensions either a
subtemporal or a combined supra and infratentorial approach is
recommended. Though microsurgical techniques have improved the
results of surgery in these difficult tumors, still there is
significant morbidity associated with their management,
especially in medial tentorial tumors.
in the posterior fossa can be excised totally without
significant problem, except when the venous sinuses are
involved. In the latter instance, total excision of the tumor
along with the involved sinus can be achieved only if either the
sinus is completely occluded or the collaterals are well
developed. Cerebellar convexity meningiomas have a propensity
to develop near the transverse-sigmoid sinus junction and hence,
sinus anatomy should be studied before planning surgery.
meningiomas are best excised by the retrosigmoid approach
in the lateral decubitus position. It is beneficial to expose
the presigmoid dura even during a retrosigmoid approach so that
the dura and the sigmoid sinus can be retracted laterally, thus
decreasing their obstruction of the surgeon’s view. It is
important to skeletonize the entire sinus from the tranverse
sinus junction to the jugular bulb in order to allow the full
freedom of movement of the sinus once the tentorium is
sectioned. When the tumor is huge with extensions into the
tentorial hiatus, and the parasellar region, or has a wide
tentorial attachment, a combined subtemporal and retromastoid
approach or a petrosal approach may be necessary.
especially, the ventral ones, pose a challenge to the surgeon,
with a high risk of morbidity. Various posterolateral approaches
have been recommended. Essentially it involves mobilizing the
vertebral artery medially and shaving off the outer third of the
occipital condyle, so that the surgeon will have unobstructed
view. Good microsurgical technique is mandatory, whichever
approach is chosen.
are better approached by
infratemporal approach of Fisch or one of its many
modifications. These tumors are inseparable from the lower
cranial nerves and hence it may be prudent to be satisfied with
subtotal excision rather than total excision with severe
postoperative morbidity. Some of these cases have en plaque
tumors over the petrous. In such cases, excision is hazardous
and unless the tumor is producing significant mass effect, it
may be periodically followed.
approached similar to that of other tumors in the same location.
The tumors in the trigone are best managed either by a parieto-occipital
approach or mid-temporal gyrus approach. Various other
approaches to the lateral ventricle have been described.
a rule, basal meningiomas need much greater vigil than convexity
course is usually uneventful unless major veins have been
sacrificed. Patients with tumors located over the central
sulcus, even with no apparent venous disturbance at surgery,
frequently have transient post-operative focal deficit on the
appropriate side of the body. Post-operative epilepsy is
frequent. Careful attention is warranted to facilitate cotical
venous drainage; mannitol is avoided unless it becomes life
saving and hypervolemic treatment helps.
a meningioma in the skull base may have a stormy post-operative
course, in spite of microsurgical techniques. The commonest
problem is that of a CSF leak with its associated
complications. A few days of prophylactic ventricular or lumbar
drainage may be useful. Cranial nerve paresis is not uncommon
and when the lower cranial nerves are involved, adequate care of
the airway with ventilatory support may be essential. A short
period of nasogastric tube feeding may be necessary.
extra-axial brain tumors, meningiomas represent the largest
group capable of recurrence. These tumors may recur, either
because of incomplete removal or a true recurrence. The overall
recurrence rates range from 13-40 per cent.
important factor in the recurrence of meningiomas was the extent
Simpson classified the types of excision into five
grades and found that while the recurrence rate was nine per
cent in grade I excision (complete macroscopic tumor removal
with excision of involved dura and bone), it was 44 per cent
in grade IV excision (intracranial tumor was left in situ).
This relationship has been confirmed by other authors. As a
meningioma is a slow growing tumor, the risk is also
directly related to the length of follow up. Complete
removal of a meningioma is not always feasible and remnants
of the tumor may be left behind in the dura, involved bone,
venous sinus wall or parts of the tumor adherent to vital
structures thus leading to recurrence.
Complete removal, including resection of dura and
Complete tumor removal with coagulation of dural
Complete tumor removal without resection or
coagulation of dural attachment.
can help to identify these dural extensions preoperatively to
help excision. These dural extensions could explain recurrence
after apparent complete tumor removal in a surface meningioma.
It is recommended that by removing an additional margin of two
cm of dura around the tumors and enbloc resection of
hyperostotic bone with ahealthy margin and the pericranium to
prevent redrowth in convexity meningiomas.
evaluating proliferative activity and tumor kinetics by the
argyrophilic method for the demonstration of nucleolar organizer
regions (Ag-NOR), flowcytometry, and bromodeoxyuridine labelling
index (BUdRLI) allow the detection of aggressive behavior in
meningiomas indicating regrowth potential. The recurrence rate
is significantly higher in atypical meningiomas than in other
histopathological types and it has been suggested that a higher
Ag-NOR count is suggestive of aggressive behaviour in
meningiomas and is associated with an increased risk of
like bone invasion and brain infiltration have been considered
important for the higher incidence of recurrence by some, but
not by others. It has been suggested that the recurrence is
more frequent in the younger age group; Some surgeons feel the
age is no predictor of recurrence.
decision for further therapy needs careful judgment. It is not
difficult to decide on reoperation in a patient with recurrence
in a resectable location and progressive symptomatology.
However, a small recurrence, especially in a difficult location
like the skull base or posterior half of the parasagittal
region, may be better followed periodically or, radiosurgery may
be considered. In case the patient becomes symptomatic with an
increase in the size of the tumor, a second operation is
justified. In cases following reoperation, those with an en
plaque tumor, and patients with anticipated problems at
excision, adjuvant radiotherapy may be considered. Hormone
therapy with anti-progesterone drugs may play a role in the
The role of
radiotherapy in meningiomas is controversial. Wara et al,
reported that after incomplete tumor removal the incidence of
recurrence at five years was 29 per cent in an irradiated group
as opposed to 74 per cent in non-irradiated patients. Radiation
has also been shown to improve survival in malignant meningiomas
and in incompletely resected and inoperable meningiomas of all
three histological types (benign, ‘aggressive benign’,
also may have a role in patients with residual/recurrent
tumors, in tumors in high risk locations, and in patients who
are unfit for surgery because of age or an associated medical
condition. Kondziolka et al, in a recent review of the results
of radiosurgery in meningiomas, found that among 24 patients
with 12-36 months follow up, 54 per cent had a reduction in
tumor volume and 38 per cent showed no change. The actuarial
two year tumor growth control was 96 per cent. Between 3-12
months, three patients developed neurological deficits because
of delayed radiation injury. However, an extended follow up is
warranted, before any definite conclusion can be drawn as to the
effectiveness of radiosurgery.
treatment of skull base meningiomas which have been incompletely
resected or have recurred, interstitial irradiation with I 125
seeds has been found to be safe and effective. Preoperative
radiotherapy in vascular meningiomas administering 30 Gy or
radiation makes surgical excision feasible six weeks after
possible mitogenic hormones (estrogen and progesterone) has been
the main focus of chemotherapy of meningioma. There is little
benefit with Tamoxifen (40mg/m2 twice daily for 4 days and 10mg
twice daily thereafter) in unresectable or refractory
meningiomas. Some benefit with 200mg daily of Mifepristone
(RU-486) has been reported. Post operative radiotherapy and 3-6
weeks of chemotherapy with cyclophosphamide, adriamycin and
vincristine, reportedly, improves survival. A high affinity
dopamine D1 binding sites in meningioma tissue using kinetic
studies have been reported. Bromocriptine is found to have some
inhibitory effect on meningiomas. dFurther
studies are required.
It is well
established that the patient with a meningioma has a high
frequency of chromosome 22 monosomy (72%) and frequently has
deletion of the long arm of chromosome 22. Recent studies have
demonstrated specific loss of chromosome 22 markers. It is
therefore believed that meningioma growth is due to loss of the
tumor suppressor gene or the anti-oncogene at the LIF locus.
The exact gene has still to be identified, clones and the
apparatus that controls the gene deciphered, which would then
lead to another major insight into the etiology of meningiomas
and it would be possible to develop diagnostic and therapeutic
strategies likely to revolutionize the management of these
have also been found in meningiomas and DNA coding for both EGF
receptors and PGF have been found. The DNA studies are
developing very fast and application of these techniques in
molecular meningioma studies increases the insight in meningioma
relationship of sex hormones and meningioma has been known since
Cushing, who noted that meningiomas had increased
pregnancy, and the relationship between the breast carcinoma and
meningioma is also well-known. Recent studies
demonstrated progesterone receptors and oestrogen receptors.
Receptor activity for progesterone has been demonstrated,
activity for oestrogen has not been demonstrated. In studies of
growth characteristics of meningiomas
bromodeoxyuridase have been used and shown to be more sensitive
than mitotic index in distinguishing a group of histologically
form malignant tumors and thereby are a better guide for the
best treatment and follow-up of a meningioma patient.