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BRAIN TUMORS

What is a brain tumor?

Metastatic brain tumor A tumor, or neoplasm, is a confined mass of abnormal tissue that proliferates rapidly and without cessation. Tumors involving the central nervous system (CNS) are classified according to the type of cells and the location of the tumor. Tumors are considered primary brain tumors if they originate in the CNS, or secondary (metastatic) brain tumors if they originate elsewhere and cells of the tumor migrate to the CNS. A tumor is benign if it is slow growing, and malignant if it is rapidly growing and readily invades surrounding brain tissue. About 24,000 primary brain tumors and an even larger number of metastatic brain tumors are diagnosed each year.

What are the different types of primary brain tumors?

The brain is composed of both nerve cells (or neurons) and glial cells. Glial cells are more numerous than neurons, and unlike neurons, they do not generate electrical signals. Instead, these cells serve to support, nourish, and insulate neurons. Tumors involving glial cells are known as gliomas. Whereas tumors involving neurons are rare, gliomas are extremely common. In fact, gliomas account for over 60% of all primary brain tumors, and there are 13,000 new cases of gliomas diagnosed each year in the United States. The most common forms of brain tumor are:

Gliomas: These are tumors derived from glial cells. Astrocytomas are gliomas involving astrocytes. These are by far the most common primary brain tumors. Glioblastoma multiformes (GBMs) or Grade III astrocytomas are the most common and the most malignant form of glioma. They account for 50% of all gliomas. Anaplastic astrocytomas or Grade II astrocytomas are of intermediate malignancy and account for 30% of all gliomas. Low grade astrocytomas or Grade I astrocytomas are the least malignant of the three. These tumors are slow growing, and occur primarily in children and young adults. Oligodendrogliomas are gliomas involving oligodendrocytes. Such tumors are uncommon and represent only 5% of all gliomas. Ependymomas are extremely rare and arise from ependymal cells. This type of tumor tends to disseminate within the cerebrospinal fluid (CSF), a fluid that circulates around the brain and serves to cushion the brain against injury.
Meningiomas: Beneath the inner surface of the skull the brain is surrounded by three membranous layers collectively known as the meninges. A meningioma is a tumor arising from the cells of one of these membranes. Thus, meningiomas do not involve brain tissue proper and the symptoms they cause are due to their compression of surrounding structures. Because these tumors do not invade surrounding tissue or spread metastatically they are classified as benign. Meningiomas are the second most common type of primary brain tumor and account for about 20% of all primary brain neoplasms. They are twice as common in females as in males.
Pituitary tumors: Pituitary tumors, or adenomas, are tumors involving the pituitary gland. The pituitary gland is attached by a thin stalk to the base of the brain. The gland is comprised of two component parts, an anterior and a posterior portion. It is an endocrine gland which releases hormones into the blood that control a variety of body functions including growth, metabolism, water balance, and menstruation. Pituitary adenomas are also benign and compress rather than invade surrounding tissue. Pituitary adenomas comprise about 10% of all primary brain tumors.
Pineal tumors: Pineal tumors are tumors involving the pineal gland, which is composed of glandular tissue, glia, and nerve terminals. Pineal tumors can either be benign or malignant and account for about 1% of all primary brain neoplasms.
Primary CNS lymphomas (PCNSLs): Primary CNS lymphomas are tumors involving the cells and tissues of that part of the lymphatic system which is associated with the CNS. These neoplasms account for 1-2% of all primary brain tumors. Patients whose immunity is compromised (e.g. AIDS patients and organ transplant recipients) are at an exceptionally high risk for the development of these tumors.

What are the prognoses of the different primary brain neoplasms?

Gliomas. Gliomas tend to become increasingly malignant over time. With respect to the astrocytomas prognosis is worst for GBMs (in which the majority of patients survive less than one year) and best for low grade astrocytomas (in which the average survival time is 8-10 years).

Meningiomas. These tumors are associated with a much more favorable prognosis. Typically, patients who have undergone surgical removal of the tumor survive for a prolonged time period.

Pituitary adenomas. Pituitary adenomas also have a favorable prognosis following surgical resection. However, 12% of such tumors recur, with most recurrences occurring after four years.

Pineal tumors. The prognosis of a pineal tumor is dependent on whether the tumor is benign or malignant. In the case of a benign pineal tumor a surgical resection of the tumor is adequate treatment. Most malignant neoplasms are correlated with a 5 year survival rate of 55% with surgical and radiation treatment.

Primary CNS lymphomas. PCNSLs are correlated with a survival of 1-2 years in patients with a competent immune system and a survival of considerably less time in a patient whose immune system is suppressed.

What complications are associated with a primary brain tumor?

Cerebral edema. Swelling around a tumor is known as peritumoral vasogenic edema. This condition can cause more neurological deficits than the tumor itself, and, if severe, can cause unconsciousness and life-threatening increases in the pressure within the skull, the intracranial pressure. Typically, edema complicates malignant tumors.
Increased intracranial pressure. As mentioned, cerebral edema can cause a dangerous increase in the pressure within the skull. Hydrocephalus, buildup of fluid within the cavities of the brain, and intracranial bleeding can also give rise to elevations in intracranial pressure (ICP). It is common for ICP to be elevated after an operation to remove a tumor. If increased, intracranial pressure can be very dangerous, and requires immediate treatment. A neuro-ICU allows careful monitoring of ICP, if necessary.
Seizures. Patients with tumors can have seizures. If the seizure is prolonged for over 30 minutes the patient is considered to be in status epilepticus. In fact, about one quarter of patients with status epilepticus have an underlying brain tumor. The longer a seizure is prolonged the greater the chance there is of brain damage. Therefore, in order to avoid the detrimental effects that seizures have on the brain it is crucial that status epilepticus be treated with specialized techniques unique to a neuro-ICU.

How are primary neoplasms of the brain treated in a neuro-ICU?

Tumors are primarily treated by neurosurgical removal of the mass, radiotherapy in which the tumor is irradiated, and chemotherapy in which drugs are given to degrade the tumor. In fact, most patients with a brain tumor will never need treatment in a neuro-ICU. A neurological intensive care unit, however, plays two fundamental roles in the care of tumor patients: it treats the complications arising from brain tumors, and it is specialized for the perioperative management of the patient (the treatment of the patient during surgery and around the time of surgery).

Peritumoral vasogenic edema is primarily and effectively treated by the administration of dexamethasone. Dexamethasone is one of a class of compounds known as glucocorticoids. The effects of dexamethasone are often dramatic, and edema is substantially lowered. This drug reduces edema by lowering the permeability of blood vessels to fluid loss. As a result, less fluid leaves these vessels and thus swelling around the tumor is limited. Because dexamethasone lowers cerebral edema it can also lower intracranial pressure.

Increased intracranial pressure is often present after surgery to remove a tumor mass. A neuro-ICU is specialized for both the monitoring and the reduction of intracranial pressure. Post-operative monitoring of ICP allows for the early detection of increased pressure and facilitates the rapid reduction of such pressure. Once ICP is correctly monitored efforts are made to reduce it.

What is involved in the perioperative management of a patient with a brain tumor?

The neuro-ICU is specialized to treat brain neoplasms and their complications during the neurosurgical removal of the tumor. Measures are routinely taken in the operating room to ensure the best possible surgical outcome.

Prevention of deep venous thrombosis and pulmonary embolism is accomplished by anticoagulation, pneumatic compression boots, and in some cases placement of a vena cava filter. Early mobilization out of bed is also critical to minimize the risk of clot formation in the legs, which occurs with prolonged immobilization. Pulmonary embolism is a common cause of sudden death in perioperative brain tumor patients. It is common for patients undergoing surgery for the removal of a brain tumor to develop a thrombus, or blood clot, somewhere in their deep venous circulation. Such a clot is known as a deep venous thrombosis (DVT), and commonly develops in the leg. In fact about 35% of patients undergoing such a surgery develop a deep venous thrombosis in their calves. Such a clot may then become dislodged (at which point it is known as an embolus) and travel to the lungs. It can then become lodged in the pulmonary artery carrying blood to be oxygenated by the lungs. This condition is known as a pulmonary embolism and is extremely dangerous.

Seizures can greatly complicate the presence of brain tumors. Therefore, anticonvulsants such as phenytoin are routinely given to patients as prophylaxis both before and during surgery.

Finally, fluid management plays an important role in minimizing brain swelling. Patients with brain tumors should only be given isotonic intravenous fluids; hypotonic fluids tend to exacerbate brain swelling.

SPINAL CORD METASTASES

What is a metastasis to the spinal cord?

One of the most common and dangerous complications of any cancer is spinal cord metastases, the spreading of cancer cells from elsewhere in the body to the spinal cord. In order to better understand this condition one must first have knowledge about the structures surrounding the spinal cord. The spinal cord is surrounded by three membranous layers collectively known as the meninges. The outermost layer is called the dura mater. Beneath the dura is the second layer, the arachnoid. This layer overlies the third layer, the pia mater, which intimately covers the spinal cord surface. Between the arachnoid and the pia mater is a space known as the subarachnoid space. Metastases can occur in the cord itself (intramedullary metastasis), in the subarachnoid space (leptomeningial metastasis), or in the epidural space, a space external to the dura mater but internal to the bony vertebral column (epidural metastases). Epidural metastases are the most common form of spinal cord metastases, and typically result from tumor spread to the vertebral column with subsequent growth inward toward the spinal cord. Epidural metastatic compression of the spinal cord occurs in 5% of all people who die of cancer (20,000 people in the U.S. each year).

What medical conditions are associated with epidural metastatic spinal cord compression?

Patients initially present with pain due to cord compression. Such pain may be axial (if limited to the central parts of the body), referred (in which the pain seems to arise from a source different from its true origin), or radicular (a pain which "shoots" down a part of the body). After the initial period of pain, cancer patients experience three characteristic symptoms of metastatic epidural compression:

Weakness or even paralysis of the body below the level of the cord that is being compressed.
Sensory loss, a loss of the sensations of touch, pain, and temperature over the area of the body below the level of the compression.
Incontinence, a lack of bladder and/or bowel control.

How are spinal cord metastases diagnosed?

Magnetic resonance imaging of the spinal cord is the best way to diagnose the cause of spinal cord compression. An alternate method is contrast myelography, in which dye is injected into the spinal fluid and X-ray pictures are taken. However, this procedure is invasive and has risks that are not associated with MR imaging.

How is epidural spinal cord compression treated in a neuro-ICU?

This condition is an emergency situation. Rapid and effective treatment is essential in preventing progressive and permanent paralysis and improving the long-term prognosis. There are two major therapies employed to treat patients with spinal cord compression due to epidural metastases:

Corticosteroids are administered. As is the case with primary tumors, metastatic tumors are treated with steroids. The agent used to treat both conditions is the glucocorticoid known as dexamethasone. Massive doses are often administered.
Focal irradiation is given. Radiotherapy should be started as soon as possible after the diagnosis is made.

In addition, recent studies have investigated the efficacy of surgery to alleviate the compression of the spinal cord. In such a surgery a portion of the vertebral column is removed. Surgical methods are aimed at relieving the compression of the spinal cord and thus reversing the symptoms associated with such compression. Although this treatment would seem to make sense, many patients do not benefit. As a result, this type of surgery is only performed in highly selected cases.

PARANEOPLASTIC SYNDROMES

What is a paraneoplastic syndrome?

Paraneoplastic syndromes are neurological disorders that arise as the "remote effect" of a cancer that does not directly involve the nervous system. The underlying cause of such syndromes is not certain, but it is theorized that these syndromes arise as a result of the body launching an immunological attack against the cells of the nervous system. It is thought that the presence of systemic cancer causes antibodies to be made against the tumor cells. Some of these antibodies, however, become directed against nerve cells, thus giving rise to the host of diseases which constitute the paraneoplastic syndromes. Paraneoplastic syndromes are very rare.

What are the different types of paraneoplastic syndromes?

The types of syndromes resulting from the remote effects of cancer are varied and only the major ones are discussed here:

Cerebellar degeneration can lead to gait ataxia (an inability to smoothly coordinate muscle movements during walking), nystagmus, and dysarthria, a disturbance of speech. Cerebellar degeneration is usually secondary to cancers of the breast, ovary, and female genital tract.
Sensory neuropathy refers to the degeneration of nerve cells specialized for the appreciation of sensations from the body surface. Therefore, people with this paraneoplastic syndrome typically experience: numbness, abnormal burning or tingling sensations in the distal extremities (paresthesia), severe pain, and an impairment of one's position sense (sensory ataxia). This syndrome usually arises secondary to lymphoma.
Lambert-Eaton syndrome (LES) is a neuromuscular disease characterized by the presence of antibodies directed against the terminals of nerves innervating voluntary muscle. Clinically the disease is characterized by limb weakness (especially of the legs), muscle stiffness, drooping eyelids (ptosis), and double vision (diplopia).
Encephalomyelitis is a term used to describe inflammation of any part of the brain or spinal cord. Different forms of encephalomyelitis can arise as the result of a remote tumor. Limbic encephalomyelitis refers to the inflammation of that part of the brain concerned with emotion, the limbic system. It is characterized by confusion, depression, agitation, anxiety, and memory disturbance. Brain stem encephalomyelitis refers to inflammation of parts of the brain stem and is characterized by double vision, speech disturbance, trouble swallowing, abnormalities of eye movements, hearing loss, and facial numbness. Myelitis is a term used to describe inflammation of the spinal cord and is characterized by weakness, muscle wasting, and involuntary muscle twitches.
Motor neuron disease is a paraneoplastic syndrome characterized by degeneration and inflammation of the nerves innervating voluntary muscle. Accordingly, this syndrome is associated with muscle weakness, muscle wasting, and muscle twitching. It is often difficult to distinguish a "pure" motor neuron disease from one caused by encephalomyelitis.

How are paraneoplastic syndromes treated in a neuro-ICU?

Most paraneoplastic syndromes do not require treatment in a neuro-ICU. However, in some cases, paraneoplastic encephalomyelitis, limbic encephalitis, and neuropathy may be severe enough to be life threatening. These instances are extremely rare. Three general strategies can be undertaken to treat these disorders:

General supportive measures such as intubation can be instituted to ensure that the patient receives an adequate supply of oxygen.
Paraneoplastic syndromes are caused by antibodies directed against the body's nerve cells. Plasmapharesis can be performed to remove pathogenic antibodies, although success is often limited. This process involves removing blood from the body, separating out the cellular elements of the blood, resuspending these cellular elements in a plasma substitute, and then reinfusing this mixture into the body. The purpose of such a procedure is to "cleanse" the blood of anti-tumor antibodies which have become directed against the cells of the nervous system. Immunosuppression with steroids can also be given.
Regardless of the type of syndrome present, these disorders can best be managed by treating the cancer from which the syndrome arises. This is usually accomplished by surgery, radiation therapy, and/or chemotherapy, which is performed once the patient is stable.

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Affiliated with New York-Presbyterian Hospital || Last updated: April 2, 2012 | Comments