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Compression of the Spinal Cord

by Michael Rubin, MDCM

Injuries and disorders can put pressure on the spinal cord, causing back pain, tingling, muscle weakness, and other symptoms.

  • The spinal cord may be compressed by bone, blood (hematomas), pus (abscesses), tumors (cancerous or not), or a ruptured or herniated disk.

  • Symptoms, such as back pain, abnormal sensations, muscle weakness, or impaired bladder and bowel control, may be mild or severe.

  • Doctors base the diagnosis on symptoms and the results of a physical examination, magnetic resonance imaging, or another imaging test.

  • Corticosteroids are often given to reduce swelling in or around the spinal cord and thus help reduce pressure on the spinal cord.

  • Depending on the cause, surgery and/or radiation therapy may be used to relieve the pressure.

Normally, the spinal cord is protected by the spine, but certain injuries and disorders may put pressure (compress) on the spinal cord, disrupting its normal function. These injuries and disorders may also compress the roots of spinal nerves, which pass through the spaces between the back bones (vertebrae), or the bundle of nerves that extend downward from the spinal cord (cauda equina).

The spinal cord may be compressed

  • Suddenly, causing symptoms in minutes or over a few hours or days

  • Slowly and gradually, causing symptoms that worsen over many weeks or months

Causes

The spinal cord may be compressed by the following:

  • Bone: If the vertebrae are broken (fractured), are dislocated, or grow abnormally (as occurs in cervical spondylosis), they may compress the spinal cord. Vertebrae that are weakened by cancer or osteoporosis may break after a slight or even no injury.

  • Connective tissue: Connective tissue that lines the spinal canal often enlarges and hardens as people age. This change narrows the spinal canal and compresses the spinal cord. (The spinal canal is the passageway that runs through the center of the spine and contains the spinal cord.)

  • An accumulation of blood (hematoma): Blood may accumulate in or around the spinal cord. The most common cause of a spinal hematoma is an injury, but many other conditions can cause hematomas. They include abnormal connections between blood vessels (arteriovenous malformations), tumors, bleeding disorders, and use of anticoagulants (which interfere with blood clotting) or thrombolytic drugs (which break up blood clots).

  • Tumors: Cancer that has spread (metastasized) to the spine or the space around the spinal cord is a common cause of compression. Rarely, a tumor within the spinal cord causes compression. The tumor may be cancerous or not.

  • A pocket of pus (abscess): Pus may accumulate outside the spinal cord or, less commonly, in the spinal cord and may compress it.

  • A ruptured or herniated disk: A herniated disk can compress spinal nerve roots (the part of spinal nerves next to the spinal cord) and occasionally the spinal cord itself.

Sudden compression typically results from

  • An injury (the most common cause), which often results in a fracture or dislocation of a vertebra

  • Hematomas and ruptured disks

However, bones weakened gradually (for example, by cancer or osteoporosis) may suddenly fracture, which can suddenly cause or worsen compression (see Compression Fractures of the Spine).

Gradual compression can develop over days to years. Typical causes vary depending on how long it takes compression to develop:

  • Days to weeks: Abscesses or tumors

  • A few months: Some chronic infections (such as spinal tuberculosis), some slow-growing tumors, or cervical spondylosis (degeneration of vertebrae and disks in the neck—see Cervical Spondylosis)

  • Many years: Usually, cervical spondylosis

What Is the Cauda Equina Syndrome?

A bundle of nerves extends downward from the bottom of the spinal cord, through the lower back bones (vertebrae) and over the bone at the base of the spine (sacrum). This bundle is called the cauda equina, which means horse’s tail in Latin, because that is what the bundle looks like.

The cauda equina may be compressed by a ruptured or herniated disk, a tumor, or an abscess. It may be damaged by an injury or swell because it becomes inflamed (as occurs in ankylosing spondylitis). The symptoms that result are called the cauda equina syndrome.

Pain is felt in the lower back, but sensation is reduced in the buttocks, genital area, bladder, and rectum—the area of the body that would touch a saddle. Thus, this condition is called saddle anesthesia. Sensation and muscle control may be impaired in the lower legs.

Other symptoms may occur:

  • Reduced sexual response, including erectile dysfunction in men

  • Retention of urine

  • Loss of bladder control (urinary incontinence)

  • Loss of bowel control (fecal incontinence)

  • Loss of reflexes in the knee and ankle

People who have the cauda equina syndrome require immediate medical attention. Surgery to relieve the compression must be done as soon as possible. Corticosteroids are usually given to reduce swelling.

Symptoms

Slight compression may cause mild symptoms if it disrupts only some nerve impulses going up and down the spinal cord. These symptoms may include

  • Discomfort or pain in the back

  • Slight muscle weakness

  • Tingling

  • Other changes in sensation

  • In men, difficulty initiating and maintaining an erection (erectile dysfunction)

Pain may radiate down a leg, sometimes to the foot. If the cause is cancer, an abscess, or a hematoma, the back may be tender to the touch in the affected area. Sometimes sensation is lost. Reflexes, including the urge to urinate, may be lost, or if compression has lasted for a few weeks or longer, reflexes may be exaggerated, sometimes causing muscle spasms and increased sweating. If compression increases, symptoms may worsen.

Substantial compression may block most nerve impulses, causing

  • Severe muscle weakness

  • Numbness

  • Retention of urine

  • Loss of bladder and bowel control

If all nerve impulses are blocked, the following result:

  • Paralysis

  • Complete loss of sensation

A beltlike band of discomfort may be felt at the level of spinal cord compression. Once compression begins to cause symptoms, the damage usually worsens from minimal to substantial unpredictably but rapidly in a few hours to a few days.

Diagnosis

  • Physical examination

  • Magnetic resonance imaging or myelography with computed tomography

People with symptoms suggesting spinal cord compression require immediate medical attention because prompt diagnosis and treatment may reverse or lessen loss of function.

Because the spinal cord is organized in a specific way, doctors can determine which part of the spinal cord is affected based on the symptoms and results of a physical examination. For example, if the legs (but not the arms) are weak and numb and bladder and bowel functions are impaired, the spine may be damaged at the midchest (thoracic) level. The location of pain or tenderness along the spine also helps doctors determine the site of the damage.

Magnetic resonance imaging (MRI) is done immediately. Or if MRI is unavailable, myelography with computed tomography (CT) is done (see Tests for Brain, Spinal Cord, and Nerve Disorders : Myelography). These tests usually show where the spinal cord is compressed and may indicate the cause. These tests can detect a fracture or dislocation of a vertebra, a herniated disk, an abnormal bone growth, an area of bleeding, an abscess, or a tumor. Myelography with CT involves doing CT of the spinal column after a spinal tap (lumbar puncture—see How a Spinal Tap Is Done) is done to inject a small amount of radiopaque dye into the space around the cord. Thus, doctors can determine whether compression completely blocks the normal flow of cerebrospinal fluid through this space.

If the cause is thought to be a fracture or dislocation due to injury, x-rays may also be taken. They provide information quickly, enabling doctors to quickly evaluate the problem.

The cause of the compression can be confirmed during surgery to relieve pressure on the spinal cord.

If MRI or myelography with CT detects an unidentifiable abnormal mass causing compression, doctors first decide whether it needs to be removed. If not, doctors usually do a biopsy. They may remove a sample of tissue for testing by inserting a needle into the mass (usually guided by CT) or sometimes by doing a surgical procedure.

Treatment

  • Usually surgery

  • Sometimes corticosteroids given intravenously

  • For tumors, usually radiation therapy (with or without surgery)

  • For abscesses or hematomas, sometimes drainage

If loss of function is partial or very recent (usually when compression occurs suddenly), the compression must be relieved immediately. When compression is detected and treated quickly, before nerve pathways are destroyed, treatment can prevent permanent damage to the spinal cord, and function is usually completely recovered. Surgery is typically needed to relieve compression. Surgery may also be needed to insert steel rods, screws, and/or pins and thus stabilize the spine.

Other treatment varies depending on the cause.

For certain disorders (such as tumors and possibly blunt injuries), high doses of corticosteroids, such as dexamethasone or methylprednisolone, are given intravenously as soon as possible. Corticosteroids can reduce swelling in or around the spinal cord, which may be contributing to compression. Immediately after corticosteroids are given, tumors are removed surgically and/or treated with radiation therapy.

If cancer is the cause, treatment usually includes surgery and/or radiation therapy.

If an abscess causes symptoms of spinal cord dysfunction (such as paralysis and loss of bowel or bladder control), a neurosurgeon surgically removes the abscess as soon as possible. Antibiotics are also given. If symptoms of spinal cord dysfunction have not developed, drawing the pus out through a needle, giving antibiotics, or both may be all that is needed.

If a hematoma is the cause, the accumulated blood is surgically drained immediately. People who have a bleeding disorder or who are taking certain anticoagulants are given injections of vitamin K and transfusions of plasma to eliminate or reduce the tendency to bleed.

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