Spinal Cord Compression

views updated

Spinal cord compression

Description

In order to understand spinal cord compression, it is useful to understand the structure of the spinal cord and to understand the difference between the spinal cord and the vertebral column. The vertebral column includes the bony structure surrounding the spinal cord and the spinal cord itself. Also an important part of the vertebral column, the intervertebral disks, are found between verte-brae. They act as shock absorbers. The spinal cord, however, is the series of nerves that runs down the hollow part of the vertebrae. Thus, the bony vertebrae and shock-absorbing disks protect the spinal cord from physical damage and compression.

Spinal cord compression occurs when something presses down with sufficient force on the nerves within the spinal cord so that they lose their ability to function properly. Although trauma, degenerative back disease, and genetic disorders can cause pressure on the spinal cord, the term spinal cord compression is usually reserved for cases in which the presence of a tumor results in pressure on the spinal cord. The tumor may originate in a number of areas and either directly or indirectly put pressure on the cord.

The spinal cord is a series of nerves bundled together that are responsible for most functions of the body, including, but not limited to, the "fight or flight" response, the movement of arms and legs, and feeling below the neck. Each nerve is responsible for different functions, such as movement, and each has a different position within the structure of the spinal cord. Thus, depending on which angle the spinal cord is compressed from, a person could experience numbness versus a loss of the ability to control muscles (often seen as an odd limp), depending on which area is compressed.

Not only do the different nerve clusters of the spinal cord have different functions, but each has nerves branching off from the spinal cord at many levels. Each of these branches controls different parts of the body. For example, nerves branching off the spinal cord in the low back control movement of the legs, and nerves branching off the spinal cord at the level of the neck are responsible for most of the movements of the arm. Thus, compression of the spinal cord at different levels can result in very different symptoms.

Vertebrae are, in order, divided into cervical, thoracic, lumbar, and sacral sections. The cervical vertebrae correspond to the neck, the thoracic vertebrae correspond to most of the torso, the lumbar vertebrae are found in the low back, and the sacral vertebrae correspond to the area of the buttocks. There are seven cervical, twelve thoracic, five lumbar, and five sacral vertebrae (although the sacrum is one bony structure and contains no inter-vertebral disks). The level of compression is indicated by using the first letter of the type of vertebra and then the number of the vertebra within the group. The topmost vertebrae are numbered lowest, so the first cervical vertebra is the vertebra closest to the head, and is known as C1. C7 is the cervical vertebra furthest down the spine. Compression of the spinal cord in this region would be known as compression at C7. The closer the compression is to the head, the more symptoms the patient is likely to have, since compression of the spinal cord affects all the levels of nerves below the area of compression that are part of the same nerve branch. For example, if movement were affected at C2 and below, a person would have difficulty using both arms and legs, whereas compression at T12 might result in just difficulty using the legs.

Importantly, the first symptom patients usually display prior to actual spinal cord compression is pain, especially pain that is not relieved by lying down, and which has lasted one month or more. This kind of pain should be sufficient to suspect imminent spinal cord compression due to cancerous causes. Also, there may be damage to nerve roots at the level of compression that can lead to symptoms in other parts of the body. For example, if the cord compression is in the lower part of the spine, then parts of the legs may be affected with numbness, tingling and loss of power and movement. Similarly, if the problem lies in the upper part of the spinal column, there may be a loss of power and sensation in parts of the arms or hands. If the cord compression becomes more severe, it can affect lower muscle functions such as bowel and bladder.

Causes

The most common cause of cancerous spinal cord compression is a vertebral metastasis . A metastasis is a cancerous lesion that arises from another tumor somewhere else in the body. Vertebral metastases account for 85% of cases of spinal cord compression, and 70% of those metastases occur in the thoracic vertebrae. About 5% to 10% of patients with cancer will develop metastases to the spinal cord. Tumors may also grow from the nerves themselves, from the connective tissue surrounding the nerves, or, rarely, from the bony vertebrae themselves. Tumors that grow from outside the vertebral column may cause pressure by either growing into the hollow space in the vertebral column or by pressuring the vertebrae into an abnormal conformation. More rarely, tumors in the verte-brae may cause compression indirectly by causing the vertebrae to collapse. Tumors that originate in the spinal cord or in the connective tissue overlying the spinal cord cause direct pressure because there is a limited area in which they can grow before impinging on the cord directly.

Treatments

If symptoms develop, prompt diagnosis and rapid treatment are crucial in order to avoid any permanent damage to the sensitive nerve tissue of the spinal cord. Usually, magnetic resonance imaging (MRI) or computed tomography (CT) scans will be performed to confirm cord compression and fully define the level and extent of the lesion. High-dose corticosteroids (oral or IV dexamethasone ) may be promptly administered in order to reduce inflammation and pressure.

The goal of therapy for spinal cord compression includes pain control, avoidance of complications, preserving or improving neurologic functions, or reversing impaired neurologic functions. Treatment usually involves treatment of the underlying tumor. For most patients with cancer-induced compression, radiation therapy is the treatment of choice. However, if radiation therapy is unavailable or if neurologic signs worsen despite medical therapy, surgical decompression should be performed. Surgery is also indicated when a biopsy is needed, when the spine is unstable, when tumors have recurred after radiation therapy, or when any abscess is present. Finally, in some tumors known to be highly chemoresponsive, chemotherapy alone or in combination with other modalities may be used.

Resources

BOOKS

Beers, Mark H., and Berkow, Robert, eds. The Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ, 1999.

PERIODICALS

Abrahm, Janet L. "Management of Pain and Spinal Cord Com pression in Patients with Advanced Cancer." Annals of Internal Medicine 131 (6 July 1999): 37.

Garner, C.M. "Cancer-related Spinal Cord Compression." American Journal of Nursing 99, no. 7 (July 1999): 34.

Husband, D.J. "Malignant Spinal Cord Compression: Prospective Study of Delays in Referral and Treatment." British Medical Journal 317, no. 7150 (4 July 1998): 18.

Michael Zuck, Ph.D.

KEY TERMS

Neurologic

—Pertaining to the nervous system.

Spinal cord

—The name given to the series of nerves which travel down the vertebral column and govern most of the functions of the body, such as movement and sensation.