Central Nervous System Carcin... Health Article

Definition

A central nervous system carcinoma is a malignant tumor arising in the cells of the brain or spinal cord.

Description

The central nervous system (CNS) is comprised of the brain and spinal cord. The CNS takes its name from the crucial role it plays in maintaining physical and mental well-being (homeostasis). The brain controls and monitors the body's activity; the spinal cord conveys information to the body from the brain, and vice versa. Consequently, a tumor in the CNS disrupts motor (e.g., standing, walking, writing) and sensory (e.g., seeing, tasting, hearing) activities.

The two major components of brain tissue are neurons (nerve cells) and glial cells. About half of all malignant CNS tumor growth starts in glial cells. Long thought to be mere space-holders, glial cells have been found to be extremely important. These cells actually protect and nourish the neurons, and may also help them transmit information. There are many different types of glial carcinomas, or gliomas.

The three layers of tissue, meninges, that cover the brain and spinal cord; and the pituitary and pineal parts of the brain, are also common sites for tumor growth. About 40% of benign (noncancerous) CNS tumors occur in the meninges, and the pituitary and pineal glands.

Some cancers that originate in organs, such as the kidneys, spread (metastasize) to the brain and spinal cord. These metastases differ from CNS carcinomas, however.

Demographics

About 35, 000 cases of CNS carcinoma are diagnosed each year. The Central Brain Tumor Registry of the United States (CBTRUS) puts the incidence of CNS tumors at 12.8 per 100, 000 person-years. The rate is slightly higher in males and slightly lower in females. Over a lifetime the chance a man will be diagnosed with and die from a CNS tumor is 1 in 200 and for a woman that rate is 1 in 263.

The older a person is the more likely he or she is to be diagnosed with CNS carcinoma. According to CBTRUS, the pediatric (individuals ages 0-19 years) incidence of CNS tumors is significantly lower, or about 3.8 per 100, 000 person-years. People under the age of 20 years also have a higher survival rate. They are five times more likely to live at least five years with a CNS tumor than are people between the ages of 45 and 64 years.

In addition to the diagnoses of primary CNS tumors (those that originate in the brain and spinal cord) is the diagnoses of metastatic cancer. Metastatic cancers are those that have spread from other primary sites, such as the breast, prostate, lungs, and colon. For every person diagnosed with a primary CNS tumor, at least four other individuals will be diagnosed with cancer that has metasta-sized to the brain and spinal cord. Occasionally, the identification of a metastatic brain cancer leads a physician to discover a cancer in another organ, or the primary site.

Causes and symptoms

The cause of CNS carcinoma is unknown. Important factors might include heredity, genetic make-up, and exposure to radiation and chemicals. Head injury might lead to meningiomas (carcinoma of the meninges). Extra or missing chromosomes or other genetic abnormalities are linked to the development of some CNS tumors. In one study a group of researchers led by T. Ballard showed pilots and flight attendants are at greater risk for CNS carcinoma, perhaps because of their frequent exposure to high levels of cosmic radiation.

Many individuals display no symptoms of CNS carcinoma until the tumor has grown large enough to exert pressure on part of the CNS. Because the skull covers the brain and the vertebral column protects the spinal cord, a growing tumor soon pushes up against a barrier of bone. The bone limits the expansion of the tumor and the cancerous and adjacent parts of the CNS become distorted. The meninges then swell in response to the distortion, producing symptoms.

Symptoms include:

• headache
• muscle weakness
• exhaustion
• nausea and vomiting
• changes in vision
• seizures

When a tumor is in the spinal cord, symptoms include back pain and incontinence (inability to control defecation and urination). Paralysis on one side of the body (hemiparesis), which often indicates a stroke in an elderly person, sometimes occurs because of a brain tumor.

Diagnosis

Seizures and difficulties with walking, speech, sight, or other day-to-day activities usually cause patients with CNS carcinoma to consult a physician. The techniques a physician uses to diagnose CNS carcinoma begins with an examination and medical history. Some combination of blood tests, x ray, computed tomography (CT), and magnetic resonance imaging (MRI) is used. If a tumor is detected with a CT or MRI scan a biopsy is usually done to determine the type of tumor.