Brain tumors are one of the more common causes of intracranial hypertension. They are subdivided into primary brain tumors, which arise from the brain tissue itself (either the neuroepithelial tissue or the neighboring mesenchymal tissues, e.g., the meninges), brain metastases, and tumors arising from the cells of the blood vessels. Brain tumors produce focal brain signs of different types depending on their location, as well as signs of intracranial hypertension that may progress more or less rapidly depending on the rate of tumor growth.

6.4.1 Overview

Epidemiology The incidence of tumors of the brain or spinal cord is approximately 5 per 100,000 persons per year in children and adolescents, and 28 per 100,000 persons per year in adults. Brain and spinal cord tumors are the most common kind of solid tumor in children; in adults, they are much rarer than the most common kinds of cancer (prostate, breast).

The frequency of different kinds of brain and meningeal tumors is shown in ▶ Fig. 6.13. The spectrum of brain tumors changes with age. In children and adolescents, the most common tumors are pilocytic astrocytoma, glioma, and medulloblastoma; in adults, the most common tumors are meningioma, glioblastoma, and pituitary tumors. Among the elderly, meningioma and glioblastoma are most common.

Classification and grading In the WHO classification, brain tumors are classified by their histologic type (for a simplified overview, see ▶ Table 6.10) and by their degree of malignity, ranked on a four-point scale ( ▶ Table 6.11): tumors of WHO grades I and II are benign, while those of grades III and IV are malignant.

Etiology Most brain tumors are of no known cause; in rare cases, they can be caused by a prior exposure to ionizing radiation or by a genetic syndrome. Examples include Li–Fraumeni syndrome (astrocytoma, primitive neuroectodermal tumors [PNET], sarcoma), Turcot syndrome (medulloblastoma, glioblastoma), and the phakomatoses (see section ▶ 6.1.8):

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  Neurofibromatosis, type 1 (neurofibroma, iris hamartoma) and type 2 (meningioma, bilateral acoustic neuroma, retinal hamartoma).

  
  
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  von Hippel–Lindau disease (hemangioblastoma of the cerebellum).

  
  
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  Tuberous sclerosis (cortical hamartoma, giant-cell astrocytoma).

  
  
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  Encephalofacial angiomatosis, that is, Sturge–Weber disease.

General clinical manifestations The general manifestations of brain tumors are presented in ▶ Table 6.12. These can progress more or less rapidly depending on the type and growth rate of the tumor. Malignant tumors typically manifest a “crescendo” course, in which overt signs and symptoms arise soon after the onset of the illness, and then worsen steadily and rapidly. The signs and symptoms of benign tumors, on the other hand, often progress slowly and insidiously, perhaps over many years. Hemorrhage into a brain tumor (either benign or malignant) may cause symptoms to arise very suddenly.

Diagnostic evaluation Neuroimaging studies are essential: the best is generally contrast-enhanced MRI (cf. ▶ Table 4.2). CT may provide useful complementary information in some cases, for example, calcifications or accompanying osseous changes, but may fail to reveal some tumors (especially low-grade gliomas). Sometimes angiography is indicated for visualization of a tumor’s blood supply.

Brain tumors generally cannot be securely diagnosed by imaging studies alone; in most cases, at least some of the tumor must be surgically removed for histologic examination. If total resection is not possible because of the location of the tumor, or contraindicated for other medical reasons, then tissue can be obtained by a stereotactic brain biopsy. A secure histologic diagnosis is needed for the optimal planning of further treatment, such as chemotherapy or radiotherapy. Moreover, some “brain tumors” turn out, on biopsy, not to be tumors at all, but rather brain abscesses, foci of demyelination, etc. In such cases, diagnostic biopsies save the patient from needless and probably harmful treatment.

Tumor markers may be useful for diagnosis and treatment.

Treatment Complete resection of the tumor is indicated whenever possible. The operability of brain tumors depends on their size, location, histologic grade, and relation to the surrounding brain tissue (infiltration vs. displacement). Not every tumor is neurosurgically accessible or fully resectable. Depending on the type of tumor, radiotherapy and/or chemotherapy may have to be used, either as the primary form of treatment or as adjuvant therapy after surgery.

The cerebral edema that usually accompanies malignant tumors is treated with corticosteroids (usually dexamethasone). Dexamethasone is also given preoperatively to reduce swelling in all cases of brain tumor with mass effect and elevated ICP. Epileptic seizures, if they arise, are treated with anticonvulsants, for example, levetiracetam. In some circumstances, prophylactic anticonvulsant administration may be helpful as well.

6.4.2 Astrocytoma and Glioblastoma

Grade IV Astrocytoma (Glioblastoma)

A distinction is drawn between primary and secondary glioblastoma. Primary glioblastoma is already a grade IV tumor at the time it arises (or is first discovered); secondary glioblastoma develops by malignant progression from a preexisting lower-grade astrocytoma or other type of glioma. Glioblastoma was historically called “glioblastoma multiforme;” the second word adds no information and has been dropped from modern classifications.

Epidemiology Glioblastoma is the most common and most malignant type of primary brain tumor. It grows by infiltration into the brain tissue. Its highest incidence is in the fifth and sixth decades of life.

Localization and growth Glioblastoma arises in a cerebral hemisphere and can spread to the contralateral hemisphere by way of the corpus callosum (butterfly glioma). Glioblastomas grow rapidly, causing rapidly progressive clinical manifestations; they are, therefore, usually diagnosed within a few weeks or (at most) months of the onset of symptoms.

Clinical features Focal neurologic and/or neuropsychological deficits arise first, sometimes accompanied by epileptic seizures, soon followed by general signs of intracranial hypertension (see ▶ Table 6.9).

Diagnostic evaluation The diagnosis can be made fairly securely from the typical appearance in neuroimaging studies ( ▶ Fig. 6.14, ▶ Fig. 6.15), though this does not obviate the need for histologic examination of tumor tissue. Contrast-enhanced MRI or CT characteristically reveals ringlike enhancement with a central nonenhancing area, corresponding to necrosis in the interior of the tumor. Intratumoral hemorrhages may also be seen. Peritumoral brain edema is often extensive, causing mass effect and midline shift.

Related posts:

Metabolic Disorders and Systemic Diseases Affecting the Nervous System Cerebellar Diseases and Other Conditions Causing Ataxia Diseases of the Brain and Meninges Nontraumatic Intracranial Hemorrhage Cerebral Ischemia and Ischemic Stroke Diseases of the Spinal Cord

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