Malignant brain tumors

Malignant brain tumors: Excerpt from Professional Guide to Diseases (Eighth Edition)

Primary malignant brain tumors account for about 10% to 30% of adult cancers. These tumors may occur at any age. The most common tumor types in adults are gliomas and meningiomas, which usually occur supratentorially (above the covering of the cerebellum). In children, incidence is generally highest before age 12, affecting 3 out of every 100,000 children; more than 1,200 new cases occur each year. The most common types in children are astrocytomas, medulloblastomas, ependymomas, and brain stem gliomas. In children, brain tumors of the central nervous system (CNS) account for 20% of all childhood cancers; they're similar in incidence to leukemias.

Causes and incidence

The cause of most brain tumors is unknown, but exposure to ionizing radiation is a known environmental risk. Additionally, most malignant tumors of the brain are of metastatic origin; 20% to 40% of patients with cancer develop brain metastasis.

Signs and symptoms

Brain tumors cause CNS changes by invading and destroying tissues and by secondary effect — mainly compression of the brain, cranial nerves, and cerebral vessels; cerebral edema; and increased intracranial pressure (ICP). (See Comparing malignant brain tumors.) Generally, clinical features result from increased ICP; these features vary with the type of tumor, its location, and the degree of invasion. (See What happens in increased ICP, page 60.) Onset of symptoms is usually insidious, and brain tumors are commonly misdiagnosed.

Diagnosis

CONFIRMING DIAGNOSIS In many cases, a definitive diagnosis follows a tissue biopsy performed by stereotactic surgery. In this procedure, a head ring is affixed to the skull, and an excisional device is guided to the lesion by a computed tomography (CT) scan or magnetic resonance imaging (MRI).

Other diagnostic tools include a patient history, a neurologic assessment, skull X-rays, a brain scan, a CT scan, MRI, and cerebral angiography. An EEG may reveal focal abnormalities. Lumbar puncture shows increased pressure and protein levels, decreased glucose levels and, occasionally, tumor cells in cerebrospinal fluid (CSF).

Treatment

Treatment includes removing a resectable tumor; reducing a nonresectable tumor; relieving cerebral edema, increased ICP, and other symptoms; and preventing further neurologic damage.

The mode of therapy depends on the tumor's histologic type, radiosensitivity, and location and may include surgery, radiation, chemotherapy, or decompression of increased ICP with diuretics, cortico-steroids, or possibly ventriculoatrial or ventriculoperitoneal shunting of CSF.

A glioma usually requires resection by craniotomy, followed by radiation therapy and chemotherapy. The combination of nitrosoureas (carmustine [BCNU], lomustine [CCNU], or procarbazine) and postoperative radiation is more effective than radiation alone.

Surgical resection of low-grade cystic cerebellar astrocytomas brings long-term survival. Treatment of other astrocytomas includes repeated surgery, radiation therapy, and shunting of fluid from obstructed CSF pathways. Some astrocytomas are highly radiosensitive, but others are radioresistant.

Treatment of oligodendrogliomas and ependymomas includes resection and radiation therapy; for medulloblastomas, resection and possibly intrathecal infusion of methotrexate or another antineoplastic drug. Meningiomas require resection, including dura mater and bone (operative mortality may reach 10% because of large tumor size).

For schwannomas, microsurgical technique allows complete resection of the tumor and preservation of facial nerves. Although schwannomas are moderately radioresistant, postoperative radiation therapy is necessary.

Chemotherapy for malignant brain tumors includes the nitrosoureas that help break down the blood-brain barrier and allow other chemotherapeutic drugs to go through as well. Intrathecal and intra-arterial administration of drugs maximizes drug actions.

Palliative measures for gliomas, astrocytomas, oligodendrogliomas, and ependymomas include dexamethasone for cerebral edema; osmotic diuretics, such as urea and mannitol, to reduce brain swelling; analgesics to control pain; and antacids and histamine receptor antagonists for stress ulcers. These tumors and schwannomas may also require anticonvulsants such as phenytoin to reduce seizures.

Special considerations

A patient with a brain tumor requires comprehensive neurologic assessment, teaching, and supportive care. During your first contact with the patient, perform a comprehensive assessment (including a complete neurologic evaluation) to provide baseline data and to help develop your care plan. Obtain a thorough health history concerning onset of symptoms. Help the patient and his family cope with the treatment, potential disabilities, and changes in lifestyle resulting from his tumor.

Throughout hospitalization:

❑Carefully document seizure activity (occurrence, nature, and duration).

❑Maintain airway patency.

❑Monitor patient safety.

❑Administer anticonvulsive drugs as ordered.

❑Check continuously for changes in neurologic status, and watch for an increase in ICP.

Alert Watch for and immediately report sudden unilateral pupillary dilation with loss of light reflex; this is an ominous change that indicates imminent transtentorial herniation.

❑Monitor respiratory changes carefully (abnormal respiratory rate and depth may point to rising ICP or herniation of the cerebellar tonsils from expanding infratentorial mass).

❑Monitor temperature carefully. Fever commonly follows hypothalamic anoxia but might also indicate meningitis. Use hypothermia blankets preoperatively and postoperatively to keep the patient's temperature down and minimize cerebral metabolic demands.

❑Administer steroids and osmotic diuretics such as mannitol as ordered to reduce cerebral edema. Fluids may be restricted to 1,500 ml/24 hours. Monitor fluid and electrolyte balance to avoid dehydration.

❑Observe and report signs and symptoms of stress ulcers: abdominal distention, pain, vomiting, and tarry stools. Administer antacids as ordered.

Surgery requires additional nursing care. After craniotomy, continue to monitor general neurologic status and watch for signs of increased ICP, such as an elevated bone flap and typical neurologic changes. To reduce the risk of increased ICP, restrict fluids to 1,500 ml/24 hours. To promote venous drainage and reduce cerebral edema after supratentorial craniotomy, elevate the head of the patient's bed about 30 degrees. Position him on his side to allow drainage of secretions and prevent aspiration. As appropriate, instruct the patient to avoid Valsalva's maneuver or isometric muscle contractions when moving or sitting up in bed; these can increase intra-thoracic pressure and thereby increase ICP. Withhold oral fluids, which may provoke vomiting and consequently raise ICP.

After infratentorial craniotomy, keep the patient flat for 48 hours, but logroll him every 2 hours to minimize complications of immobilization. Prevent other complications by paying careful attention to ventilatory status and to cardiovascular, GI, and musculoskeletal functions.

❑Radiation therapy is usually delayed until after the surgical wound heals, but it can induce wound breakdown even then, so observe the wound carefully for infection and sinus formation. Because radiation may cause brain inflammation, watch for signs of rising ICP.

❑Because the nitrosoureas — BCNU, CCNU, and procarbazine — used as adjuncts to radiotherapy and surgery can cause delayed bone marrow depression, tell the patient to watch for and immediately report any signs of infection or bleeding that appear within 4 weeks after the start of chemotherapy. Before chemotherapy, give prochlorperazine or another antiemetic, as ordered, to minimize nausea and vomiting.

❑Teach the patient and his family signs of recurrence; urge compliance with treatment regimen.

❑Because brain tumors may cause residual neurologic deficits that disable the patient physically or mentally, begin rehabilitation early. Consult with occupational and physical therapists to encourage independence in daily activities and improve the quality of life. As necessary, provide aids for self-care and mobilization, such as bath room rails for the wheelchair patient. If the patient is aphasic, arrange for consultation with a speech pathologist.

❑Legal advice is helpful in forming advance directives such as power of attorney in cases where continued physical or intellectual decline is likely.

❑Refer the patient for counseling and to national and local support groups to help him cope with this disorder.

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Book Source Details

• Book Title: Professional Guide to Diseases (Eighth Edition)
• Author(s): Springhouse
• Year of Publication: 2005
• Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.

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More About This Book: Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X

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