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Intracranial Neoplasms

Dr. Hawar Adnan

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Definition

• A cerebral neoplasm can be defined as a benign or malignant expanding lesion whose constituent cells multiply without restraint and form a mass within the cranial or spinal cavity.

• There are two main types: • (1) primary tumors, made up of astrocytes,

oligodendrocytes, ependymocytes, (together called gliomas); special arachnoidal fibroblasts (meningiomas); neuroblasts-medulloblasts

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• (2) secondary tumors, which are metastatic carcinomas from lung, breast, etc., and lymphomas.

• All of these tumors cause symptoms by infiltrating, displacing, and compressing brain tissue and provoking seizures.

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Etiology

• Little is known about etiology.• Familial occurrence is low but not insignificant.• EB virus has been implicated in lymphomas of

the brain. • The age of the patient is also a factor;

medulloblastoma, pilocytic astrocytoma, pinealoma, optic glioma, and brainstem glioma are essentially tumors of childhood.

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Pathophysiology

• As a group, the gliomas arise in one or a few foci in the cerebral white matter, central gray matter, brainstem, or cerebellum. Their borders are inobvious, and they cannot be completely excised.

• The well-differentiated tumor cells of an astrocytoma and oligodendroglioma infiltrate and displace the normal cells and myelinated fibers.

• Undifferentiated glial cells (glioblastoma multiforme, grade III astrocytoma) proliferate more rapidly, often outstripping their blood supply and becoming necrotic and hemorrhagic in places.

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• With tumor growth there is compression of venules in the adjacent cerebral white matter and a disruption of the blood-brain barrier.

• Plasma proteins seep into the cerebral white matter, causing vasogenic or localized cerebral edema.

• As the mass in the cerebrum or cerebellum increases in size, intracranial pressure rises and adjacent normal brain is displaced.

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• Because of the compartmentalization of the cranial cavity by dura (falx, tentorium), pressure from a mass in one compartment causes a shift of brain tissue into another compartment, where the pressure is lower.

• The deficits produced by these displacements, which appear late in the course of tumor growth, are added to those of the tumor itself.

• This may lead to tissue herniation from one compartment to another.

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Types of Herniation

1. cingulate herniation under the falx

2. downward transtentorial (central) herniation

3. uncal herniation over the edge of the tentorium,

4. cerebellar tonsillar herniation into the foramen magnum

• Coma and ultimately death result when (2), (3), or (4) produces brainstem compression.

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Types of Herniation

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CLINICAL MANIFESTATIONS

1. Progressive focal neurologic deficits.

2. seizures .

3. “nonfocal” neurologic disorders (headache, dementia, personality change, gait disorder).

• Nonfocal disorders are due to increased intracranial pressure (ICP), hydrocephalus, or diffuse tumor spread.

• Elevated ICP suggested by vomiting, drowsiness, papilledema, impaired lateral gaze, headache that intensifies with recumbency.

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• Strokelike onset may reflect hemorrhage into tumor or development of acute hydrocephalus.

• Brain tumors may be large at presentation if located in clinically silent region (i.e., prefrontal) or slow-growing .

• frontal, or temporal lobe tumors may present as psychiatric disorder.

• Systemic symptoms (malaise, anorexia, weight loss, fever) suggest metastatic rather than primary brain tumor.

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Diagnostic Tests

• Primary brain tumors have no serologic features of malignancy such as an elevated ESR or tumor-specific antigens, unlike metastases.

• Neuroimaging (CT or MRI) reveals mass effect (volume of neoplasm and surrounding edema) and contrast enhancement (breakdown of blood-brain barrier).

• CSF exam is limited to diagnosis of possible meningitis or meningeal metastases but may cause brain herniation if mass effect or hydrocephalus present.

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Treatment

• Surface tumors such as meningiomas and acoustic neuromas are amenable to complete surgical removal.

• Meningiomas of the base of the brain may infiltrate bone and can be excised only partially. Radiation therapy is then given.

• For gliomas, the common practice is excisional biopsy followed by radiation therapy.

• Symptomatic treatment includes glucocorticoids (dexamethasone 12–20 mg/d in divided doses) to temporarily reduce edema; prophylaxis with anticonvulsants for tumors involving cortex or hippocampus; and low-dose subcutaneous heparin for immobile pts.

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Glioblastoma multiforme

• 20% of all intracranial tumors, 55% of all gliomas; mainly affect cerebral hemispheres but may affect all parts of brain and cord.

• It is widely infiltrative ( highly malignant).• survival is about 12 months in most cases.

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Malignant astrocytoma (glioblastoma)

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Astrocytomas (low grade)

• 25–30% of cerebral gliomas; • In adults, common sites are cerebral

hemispheres • In children, brainstem and cerebellum; • It is a slowly growing tumor that has a

tendency to form cysts; • Survival rate is for many years.

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Oligodendroglioma

• 5–7% of intracranial gliomas. • Frontal lobes are the most common sites. • It is a slowly growing tumor.• Characteristically forms calcifications. • Survival for many years if low-grade

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Oligodendroglioma

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Ependymoma

• Derived from ependymal cells• Common sites are fourth ventricle (particularly

in children), conus medullaris, and filum terminale.

• Survival depends on degree of anaplasia

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Meningioma

• Extraaxial mass attached to dura; dense and uniform contrast enhancement is diagnostic.

• 15% of all primary intracranial tumors• highest incidence occurs in seventh decade;

more frequent in women. • Very slow growing; symptoms depend on

tumor site.

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Meningioma

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Primary CNS lymphoma

• B cell malignancy; most occur in immunosuppressed pts (organ transplantation, AIDS).

• May present as a single mass lesion (immunocompetent pts) or as multiple mass lesions or meningeal disease (immunosuppressed pts).

• Dramatic, transient responses occur with glucocorticoids.

• In immunocompetent pts chemotherapy and RT may increase survival to18 months; AIDS-related cases survive about 3 months.

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Primary CNS lymphoma

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Acoustic neuroma (Schwannoma)

• Usually solitary• may be part of neurofibromatosis, either solitary

(type I) or bilateral (type II)• unilateral neurosensory deafness, loss of balance,

facial weakness and loss of sensation, later ataxia of ipsilateral limbs and gait and raised intracranial pressure.

• MRI reveals dense, uniformly enhancing tumor at the cerebellopontine angle.

• Surgical excision may preserve hearing.

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Schwannoma

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MEDULLOBLASTOMA

• Highly malignant tumors of childhood.• Age of onset is 4-8.• Arises from neuroectodermal cells.• Medulloblastomas occur in the posterior fossa

and frequently disseminate along CSF pathways.

• begins with vomiting, headaches; later, squint, ataxic gait, falling, and papilledema.

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MEDULLOBLASTOMA

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Tumors Metastatic to the Nervous System

• Most commonly hematogenous.• Primary tumors that commonly metastasize to

the nervous system are from lung, breast and malignant melanoma.

• Brain metastases are well demarcated by MRI and enhance with gadolinium.

• CSF cytology is unnecessary as intraparenchymal metastases rarely shed cells into CSF.

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• One-third of pts presenting with brain metastasis have unknown primary (ultimately small cell lung cancer and melanoma are the most frequent).

• Screening for the primary site includes:

1. Skin and thyroid gland examination.

2. liver function tests

3. CT of chest, abdomen, and pelvis

4. blood carcinoembryonic antigen (CEA)

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• Treatment is palliative: glucocorticoids, anticonvulsants, or RT may improve quality of life.

• Whole-brain RT is given, because multiple microscopic tumor deposits are likely throughout the brain.

• If a single metastasis is found, it may be surgically excised followed by whole-brain RT.

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Brain metastasis

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END