Brain tumors, malignant

With an incidence of 4.5 per 100,000 patients, malignant brain tumors (gliomas, meningiomas, and schwannomas) are common (slightly more so in men than in women).

Tumors may occur at any age. In adults, incidence is generally highest between ages 40 and 60. The most common tumor types in adults are gliomas and meningiomas; these tumors are usually supratentorial (above the covering of the cerebellum).

In children, incidence is generally highest before age 1 and then again between ages 2 and 12. The most common tumors in children are astrocytomas, medulloblastomas, ependymomas, and brain stem gliomas. In children, brain tumors are one of the most common causes of death from cancer.

Causes

Some tumors are congenital, whereas others are hereditary. The cause of most brain tumors is unknown.

Signs and symptoms

Brain tumors cause central nervous system 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). Generally, signs and symptoms result from increased ICP; these vary with the type of tumor, its location, and the degree of invasion. The onset of signs and symptoms is usually insidious, and brain tumors are commonly misdiagnosed. (See Clinical features of malignant brain tumors, pages 116 to 118.)

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. Lumbar puncture shows increased pressure and protein levels, decreased glucose levels and, occasionally, tumor cells in cerebrospinal fluid (CSF).

Treatment

Remedial approaches include removing a resectable tumor; reducing a nonresectable tumor; relieving cerebral edema, increased ICP, and other signs and 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 a diuretic, corticosteroid or, possibly, ventriculoatrial or ventriculoperitoneal shunting of CSF.

❑ Gliomas. Treatment 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.

❑ Astrocytomas. 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.

❑ Oligodendrogliomas and ependymomas. Treatment includes resection and radiation therapy.

❑ Medulloblastomas. Treatment involves resection and, possibly, intrathecal infusion of methotrexate or another antineoplastic.

❑ Meningiomas. Treatment requires resection, including dura mater and bone (operative mortality may reach 10% because of large tumor size).

❑ 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 a nitrosourea to help break down the blood-brain barrier and permit other chemotherapeutic drugs to go through as well. Intrathecal and intra-arterial administration of drugs maximizes drug action.

Palliative measures for gliomas, astrocytomas, oligodendrogliomas, and ependymomas include dexamethasone for cerebral edema and an antacid and a histamine-receptor antagonist for stress ulcers. These tumors and schwannomas may also require an anticonvulsant.

Special considerations

❑  Perform a comprehensive assessment (including a complete neurologic evaluation) to provide baseline data and guide subsequent care. Obtain a thorough health history concerning onset of symptoms.

❑  Assist the patient and his family in coping with the treatment, potential disabilities, and changes in lifestyle resulting from his tumor.

Throughout hospitalization, perform the following:

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

❑  Maintain airway patency.

❑  Monitor patient safety.

❑  Administer an anticonvulsant as required.

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

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

❑  Carefully monitor respiratory changes.

Clinical tip  Abnormal respiratory rate and depth may point to rising ICP or herniation of the cerebellar tonsils from an 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 a steroid and an osmotic diuretic, such as mannitol, as needed, to reduce cerebral edema. Fluids may be restricted to 1½ qt (1.4 L) every 24 hours. Monitor fluid and electrolyte balance to avoid dehydration.

❑  Observe the patient for signs and symptoms of stress ulcers: abdominal distention, pain, vomiting, and black, tarry stool. Administer an antacid and a histamine-2-receptor antagonist as needed.

Surgery requires additional patient care. After craniotomy, perform the following:

❑ 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 1½ qt (1.4 L) every 24 hours.

❑  Elevate the head of the patient’s bed about 30 degrees to promote venous drainage and reduce cerebral edema after supratentorial craniotomy. 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; they can increase intrathoracic 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 function.

❑  Observe the wound carefully for infection and sinus formation. Radiation therapy is usually delayed until after the surgical wound heals, but it can induce wound breakdown even then.

❑  Watch for signs of rising ICP because radiation may cause brain inflammation.

❑  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 because nitrosoureas used as adjuncts to radiotherapy and surgery can cause delayed bone marrow depression.

❑  Before chemotherapy, give prochlorperazine or another antiemetic, as needed, to minimize nausea and vomiting.

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

❑  Begin rehabilitation early because brain tumors may cause residual neurologic deficits that handicap the patient physically or mentally.

❑  Consult with occupational and physical therapists to encourage independence in daily activities.

❑  As necessary, provide aids for self-care and mobilization, such as bathroom rails for wheelchair patients.

❑  If the patient is aphasic, arrange for consultation with a speech pathologist.

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Book Source Details

• Book Title: Handbook of Diseases
• Author(s): Springhouse
• Year of Publication: 2003
• Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.

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