INTRODUCTION

Meningiomas are tumors that are derived from the meningothelial cells that invest the arachnoid membrane. Therefore, meningiomas that occur outside the brain parenchyma are extra-axial tumors.¹ They are more common in women than in men, with 65% of all diagnosed meningiomas occurring in women in the fifth and sixth decades of life. They are rare in children; only 1.5% of all meningiomas occur in childhood and adolescence, with boys predominantly affected.² The localizations and clinical manifestations of pediatric meningiomas show differences from those in adults.³ That malignant meningiomas are very destructive and grow more rapidly than benign meningiomas makes a difference in their clinical behavior, and this separates the evaluation of malignant meningiomas. Limb paresis and headache are the most common clinical signs.⁴ Meningiomas may arise from any part of the lining in both the cranial vault and spinal cord. They often occur along the intracranial venous sinuses, which they may invade. Meningiomas produce numerous neurologic symptoms by several mechanisms, depending on their localization, size, and the function of the particular area.⁵ Their symptoms and signs include headache, seizure, personality changes, parkinsonism, and focal neurologic deficits such as hemiparesis, visual field defect, and cranial nerve disturbance. Because meningiomas are very slow-growing tumors, patients may have subtle symptoms for a long time before the diagnosis is made.⁶ Because of slow growth, the brain adapts to changes. Compensatory mechanisms fail in the advanced stages of meningioma growth.⁷ Meningiomas smaller than 2.0 cm in diameter are generally discovered in a postmortem study in middle-aged and elderly persons without having caused manifestations. As many as one third of all meningiomas are asymptomatic at the time of their diagnosis and are discovered when radiologic imaging is performed for unrelated symptoms.

FOCAL NEUROLOGIC DEFICITS

Focal neurologic deficits are due to a direct mass effect on surrounding structures, which are either destroyed or suffer impairment of function. The location of the tumor may be associated with specific neurological symptoms as headaches, muscle weakness, confusion, and cranial nerve disturbance. Focal neurologic deficits caused by meningiomas generally relate to compression (cranial nerve, brain, or spinal cord) and can be predicted from the site of origin of the tumor. Many meningiomas arising from the anterior skull base are large at presentation and psychomotor symptoms and behavioral disturbances especially personality disintegration. When tumors are close to the skull, they frequently erode the cranial bones. Sometimes they give rise to an exostosis on the external surface of the skull.

Parasagittal and falcian meningiomas are the most common localization of meningiomas (30%–50%).⁸ In considering the symptoms of both of these tumors, it is useful to divide them according to the area from which they arise: anterior, middle, and posterior thirds of the sagittal sinus and falx.⁹ Meningiomas arising from the middle third of the sagittal sinus and falx are the most common and present with focal seizures or gradual loss of motor and sensory function usually beginning in the lower extremity. Meningiomas arising from the anterior third tend to have a more insidious onset and often become large before a diagnosis is made. There may be a gradual change in personality and mental functions. Headache is common (Fig. 11-1).

FIGURE 11-1 The 41-year-old female patient was admitted to hospital complaining of headache and right sided-lower extremity motor weakness. A, Axial. B, Coronal. C, Sagittal contrast-enhanced T1 weighted magnetic resonance imaging (MRI) revealed left parasagittal falx meningioma. Postoperative noncontrast T1 weighted MRI (D) and contrast enhanced coronal (E) and sagittal (F) MRI.

(Courtesy of Prof. Pamir.)

Convexity meningiomas may arise from any area of the dura over the convexity but are more common along the coronal suture and near the parasagittal region. They grow on the surface and may not produce symptoms until they reach a large size. Different symptoms and signs related to specific locations have been defined. For example, meningiomas in the parietal lobe of the dominant hemisphere may cause Gerstmann syndrome (acalculia, agraphia, finger agnosia, and right–left disorientation), nondominant parietal lobe meningiomas lead to tactile, visual extinction and neglect of the contralateral side, occipital lobe tumors result in visual field defects such as homonymous hemianopsia.

Olfactory groove meningiomas can arise from arachnoidal cells along the cribriform plate and frontosphenoid suture and account for 10% of intracranial meningiomas.¹⁰ These meningiomas may slowly expand bilaterally and push on frontal lobes. The diagnosis depends on the findings of ipsilateral or bilateral anosmia or ipsilateral or bilateral blindness often with optic atrophy, headache, and mental changes.¹¹ Inferior visual field defect is the most common sign. Olfactory groove meningiomas cause Foster Kennedy syndrome of unilateral optic atrophy and contralateral papilledema. The syndrome is originally described in these meningiomas but occurs in only a small number of patients. Other common symptoms are personality changes, cognitive decline and psychiatric disturbances.¹² Mental changes such as apathy, abulia, akinesia, confusion, forgetfulness, and so forth are noticed particularly by family members over several years, so these symptoms may be the initial presentation.

Suprasellar meningiomas originating from the tuberculum sellae,¹³ diaphragma sellae and planum sphenoidale are uncommon. They represent about 3% to 10% of all intracranial meningiomas.¹ The symptoms of suprasellar meningiomas include visual loss, loss of smell, mental disorders, epilepsy, and headache.¹⁴ Asymmetric visual loss, either monocular or binocular, is the most common symptom leading to diagnosis. Other symptoms such as dizziness, incontinence, tinnitus, fainting spells, motor deficits, somnolence, and endocrinologic disturbances are noted. Among suprasellar meningiomas, tuberculum sellae meningiomas are the most common. They cause bitemporal hemianopia, in contrast to other suprasellar meningiomas, and usually no endocrinologic disturbances are present. Cushing was the first to describe the syndrome caused by tuberculum sellae meningiomas.^15,16

Sphenoid wing meningiomas are located over the lesser wing of the sphenoid bone. The sphenoid wing is the third most common site for intracranial meningiomas.¹⁷ As meningiomas that are situated in sphenoid wing grow, they may expand medially into the wall of the cavernous sinus, anteriorly into the orbit, and laterally into the temporal bone. Growth of tumors in the inner wing and orbit most often causes direct damage to the optic nerve, leading mainly to progressive decrease in visual acuity; loss of color vision, especially central defects in the visual fields; and afferent pupillary defects. If meningiomas continue to grow and compress the optic nerve totally, first optic atrophy in one eye occurs, then blindness develops. Tumors growing into cavernous sinus cause damage to cranial nerves (occulomotor, trochlear, abducens, ophthalmic, and maxillary division of trigeminal nerve), sympathetic fibers, and the venous circulation. Thus damage to these structures leads to diplopia, Horner’s syndrome, palpebral swelling, and exophthalmos. Most prominent among these symptoms is a slowly developing unilateral exophthalmos. The abducens nerve is often the first affected cranial nerve, leading to diplopia with lateral gaze. Globoid type meningiomas may extend intracranially, so they may lead to seizure disorders or impairment of neurologic functions such as motor weakness. This type of meningioma causes different clinical syndromes. Variants of this clinical syndrome include anosmia, oculomotor palsies, Tolosa–Hunt syndromes (painful ophthalmoplegia), sometimes Foster Kennedy syndrome (papilledema of the other eye), and mental changes.

Clinoidal meningiomas are also termed medial or inner wing sphenoidal meningiomas. They arise from the meningeal covering of the anterior clinoid process.¹⁸ Symptoms and signs include visual disturbances, involvement of cranial nerves (III, IV, V, VI, and VII), headache, and seizure (Fig. 11-2).

FIGURE 11-2 A 65-year-old man was admitted with the complaints of visual loss on left eye. A, Axial. B, C, Coronal contrast-enhanced MRI revealed left clinoidal meningioma.

(Courtesy of Prof. Pamir.)

Optic nerve sheath meningiomas are responsible for 1% to 2% of all meningiomas. The symptoms of optic nerve sheath meningiomas depend on localization in the orbit, the optic canal, or intracranially.¹⁹ They are usually unilateral. Although patients typically present with initially decreased or blurred vision in the affected eye, at examination the vision acuity may be normal. In large tumors, blindness develops and swollen optic disc or optic atrophy and optociliary shunt vessels are seen on funduscopic examination.^20,21 The predominant feature of these tumors is early visual loss (Fig. 11-3). Neurofibromatosis type II is associated with meningiomas, especially optic nerve sheath meningiomas.²² In these patients, family history is important.

FIGURE 11-3 A 26-year-old man was admitted to hospital complaining of bilateral complete visual loss. A, Axial. B, Coronal. C, D, Sagittal contrast-enhanced MRI revealed right (C) and left (D) optic nerve sheath meningiomas.

(Courtesy of Prof. Pamir.)

Cavernous sinus meningiomas involving the cavernous sinus may start in the sinus or grow into it as part of a larger tumor involving the medial sphenoid wing, orbit, other areas of the middle fossa, or clivus or petrous bone. Their symptoms are similar to those discussed previously in sphenoid wing meningiomas, but they may be more mild or nonprogressive.²³ Patients with these tumors are usually admitted to clinics with complaints of visual loss.

Intraventricular meningiomas are usually located in the trigone of the lateral ventricle.²⁴ Lateral ventricular meningiomas are often silent tumors with papilledema, headache, weakness, mental changes, and visual field defects as the most common problems.

Infratentorial (posterior fossa) meningiomas are responsible for 10% of all meningiomas.²⁵ Meningiomas are classified as petroclival, posterior surface of the petrous bone (cerebellopontine angle), cerebellar convexity, foramen magnum, and jugular foramen. Symptoms and signs include headache, cerebellar dysfunction, and tinnitus (Fig. 11-4).

FIGURE 11-4 A 70-year-old female was admitted with the complaint of gait disturbance. A, Coronal. B, Sagittal. C, Axial, contrast-enhanced cranial MRI revealed left tentorial meningiomas. There is compression of the left cerebellar hemisphere and fourth ventricle. D, Postoperative contrast-enhanced axial T1.

(Courtesy of Prof. Pamir.)

Cerebellopontine angle meningiomas are the second most common tumor to arise in the cerebellopontine angle (CPA) after acoustic neuromas. CPA meningiomas arise lateral to the trigeminal nerve. Symptoms and signs of meningiomas localized to the CPA include loss of hearing, headache, cerebellar dysfunction, facial pain, or numbness secondary to involvement of the trigeminal nerve, long tract signs arising from involvement of the corticospinal tract, and vestibular dysfunction secondary to involvement of the vestibulocochlear nevre. Meningiomas also may involve the lower cranial nerves.²⁶

Cerebellar convexity meningiomas constitute 1% to 2% of all meningiomas and 10% to 20% of posterior fossa meningiomas.²⁵ They are frequently adjacent to the transverse sinus, sigmoid sinus, and torcular Herophili. They may attach to the cerebellar dura, the petrous dura, or the tentorium. Some of these tumors may become large before they produce symptoms. Patients may present with symptoms and signs characteristic of posterior fossa lesions: headache and cerebellar dysfunction.

Petroclival meningiomas arise from the clivus and the petrous bone medial to the fifth cranial nerve. They may grow out along the petrous pyramid or into the cavernous sinus and middle fossa. Symptoms are secondary to several factors, the first being involvement of cranial nerves, especially the first trigeminal, vestibulocochlear, facial, abducens, and oculomotor nerves (Fig. 11-5). Deficits of cranial nerves III, IV, and VI are uncommon. Other symptoms include cerebellar or brain stem compression with involvement of the corticospinal tract. Rarely, petroclival meningiomas may invade the basilar artery and its branches and thus cause basilar arterial insufficiency.

FIGURE 11-5 A 56-year-old man was admitted to the neurosurgery clinic with the complaints of diplopia and left sixth cranial nerve palsy. A, Axial contrast-enhanced cranial MRI revealed left petroclival meningioma and (B) after gamma-knife treatment.

(Courtesy of Prof. Pamir.)

Foramen magnum meningiomas symptoms and signs include unilateral neck pain; Lhermitte’s sign; involvement of the glossopharyngeal, vagus, and accessory cranial nerves; cold dysesthesias; progression of motor and sensory deficits starting in one arm and spreading to the other limbs; and atrophy of the hand muscles (Fig. 11-6). Patients may also demonstrate slow athetosis-like movements of their arms, hands, and particularly fingers due to disturbance in position sense.

FIGURE 11-6 A 50-year-old woman was admitted with the complaints of quadriparesia. Sagittal (A) and axial (B) contrast-enhanced cranial MRI revealed foramen magnum meningioma, and postoperative sagittal (C) and axial (D) images.

(Courtesy of Prof. Pamir).

Jugular foramen meningiomas are an unusual location for meningiomas, accounting for 4% of posterior fossa meningiomas. Meningiomas of the posterior fossa involve the jugular foramen more often by extension from another site of origin. The clinical presentation of jugular foramen meningiomas is a combination of lower cranial nerve involvement (IX, X, XI, and XII). Patients with these tumors may also complain of hearing loss, pulsatile tinnitus, and middle ear mass.^27,28

Spinal meningiomas are usually located in the thoracic region.²⁹ In one study, a comprehensive series of 174 spinal meningiomas, 70% of the patients had little or no neurologic impairment and 30% had a significant or severe impairment preoperatively.³⁰ The predominant symptom is pain in patients with these meningiomas.²⁹