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Nerve Root Disorders

(Radiculopathies)

By

Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Dec 2020| Content last modified Dec 2020
Click here for the Professional Version
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Nerve root disorders result from sudden or long-term pressure on the spinal nerve root.

  • Nerve root disorders usually result from a herniated disk or osteoarthritis in the spine.

  • These disorders can cause pain, abnormal sensations, and/or muscle weakness in the area of the body they supply.

  • Doctors diagnose nerve root disorders based on results of imaging tests, electrodiagnostic testing, and tests to identify the cause.

  • Doctors treat the cause if possible and give drugs to relieve the pain, including over-the-counter pain relievers (such as nonsteroidal anti-inflammatory drugs or acetaminophen) and corticosteroids.

Nerve roots are the short branches of a spinal nerve Cranial nerves and spinal nerves The peripheral nervous system consists of more than 100 billion nerve cells (neurons) that run throughout the body like strings, making connections with the brain, other parts of the body, and... read more . Spinal nerves exit the spinal cord along the length of the spine. Each spinal nerve contains two nerve roots: one motor and one sensory. (Motor nerve roots contain nerve fibers that carry commands from the brain and spinal cord to muscles. Sensory nerve roots contains nerve fibers that carry sensory information about such things as touch, position, pain, and temperature from the body to the spinal cord.) After exiting the spinal cord, the two nerve roots join to form a single spinal nerve. Each spinal nerve then goes between two back bones (vertebrae) in the spine to connect to a specific area of the body. The surface of the skin is divided based on these specific areas, which are called dermatomes. A dermatome is an area of skin whose sensory nerves all come from a single spinal nerve root.

The Spine

A column of bones called vertebrae make up the spine (spinal column). The vertebrae protect the spinal cord (a long, fragile structure contained in the spinal canal), which runs through the center of the spine. Between the vertebrae are disks composed of cartilage, which help cushion the spine and give it some flexibility.

Spinal nerves: Emerging from the spinal cord between the vertebrae are 31 pairs of spinal nerves. Each nerve emerges in two short branches (roots)—motor and sensory—which join to form a spinal nerve.

The motor roots carry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles.

The sensory roots carry information to the brain from other parts of the body.

Cauda equina: The spinal cord ends about three fourths of the way down the spine, but a bundle of nerves extends beyond the cord. This bundle is called the cauda equina because it resembles a horse's tail. The cauda equina carries nerve impulses to and from the legs, lower intestine, and bladder.

How the Spine Is Organized

Dermatomes

The surface of the skin is divided into specific areas, called dermatomes. A dermatome is an area of skin whose sensory nerves all come from a single spinal nerve root. (Sensory nerves carry sensory information—about such things as touch, pain, temperature, vibration, and position of a body part—to the spinal cord.)

  • There are 8 pairs of sensory nerve roots for the 7 cervical vertebrae.

  • Each of the 12 thoracic, 5 lumbar, and 5 sacral vertebrae has one pair of spinal nerve roots.

  • At the end of the spinal cord, there is a pair of coccygeal nerve roots, which supply a small area of the skin around the tailbone (coccyx).

There are dermatomes for each of these nerve roots.

Sensory information from a specific dermatome is carried by sensory nerve fibers to the spinal nerve root of a specific vertebra. For example, sensory information from a strip of skin along the back of the thigh, is carried by sensory nerve fibers to the 2nd sacral vertebra (S2) nerve root.

Dermatomes

Causes

The most common cause of nerve root disorders is

A herniated disk can cause a nerve root disorder by putting pressure on the nerve root next to it.

Less commonly, a tumor or other mass (such as an abscess) puts pressure on a nerve root.

Symptoms

Symptoms of nerve root disorders depend on which nerve root is affected. Pain, abnormal sensations, and/or muscle weakness occur in the area of the body supplied by the nerve root. The pain may feel like an electric shock that radiates through the affected area. Muscles may waste away and/or twitch. People may be paralyzed.

Pain may be worsened by movement, including moving the back, coughing, and sneezing.

If the lowest roots of the spinal cord (the cauda equina Cauda Equina Syndrome Cauda equina syndrome occurs when the bundle of nerves that extends from the bottom of the spinal cord is compressed or damaged. The most common cause of cauda equina syndrome is a herniated... read more ) are affected, people may have weakness in the legs, urinary problems (such as incontinence or retention of urine), lose control of their bowels, and lose sensation in the buttocks, genital area, bladder, and rectum. Men may have trouble having an erection. This disorder, called cauda equina syndrome, is a medical emergency. The problem—such as a herniated disk, an abscess, a tumor, or a blood clot—that is putting pressure on the cauda equina must be corrected to prevent permanent nerve damage.

Diagnosis

  • Imaging tests

  • Sometimes electrodiagnostic tests

Doctors ask about symptoms and do a physical examination. The findings provide clues to the diagnosis and help doctors determine where the problem is.

Magnetic resonance imaging (MRI) or computed tomography (CT) is done to confirm the diagnosis. MRI shows the spinal cord, as well as abnormalities in the soft tissues around the cord, such as abscesses, hematomas (collections of blood), tumors, and ruptured disks, and in bone, such as tumors, fractures, and cervical spondylosis Cervical Spondylosis Cervical spondylosis is degeneration of the bones in the neck (vertebrae) and the disks between them, putting pressure on (compressing) the spinal cord in the neck. Osteoarthritis is the most... read more .

If MRI cannot be done and if results of CT are unclear, myelography is done. For myelography, a radiopaque contrast agent (which can be seen on x-rays) is injected into the space around the spinal cord, and x-rays are taken. CT myelography may also be done. CT myelography can provide detailed images of the spinal cord and surrounding bone.

Electrodiagnostic tests (electromyography and nerve conduction studies Electromyography and Nerve Conduction Studies Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more Electromyography and Nerve Conduction Studies ) are done to confirm that symptoms are caused by compression of the spinal nerve rather than by problems in the spinal cord or in a nerve plexus Plexus Disorders Plexuses (networks of interwoven nerve fibers from different spinal nerves) may be damaged by injury, tumors, pockets of blood (hematomas), or autoimmune reactions. Pain, weakness, and loss... read more (a network of nerve fibers, where fibers from different spinal nerves are sorted and recombined to serve a particular area of the body). However, these tests cannot always identify the cause.

If imaging tests do not identify a cause, a spinal tap is done, and doctors analyze the fluid that surrounds the brain and spinal cord (cerebrospinal fluid) to check for infections. Doctors also measure the blood glucose level after people have fasted to check for diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more .

Treatment

  • Treatment of the cause

  • Treatment of pain

  • Surgery (usually as a last resort)

Causes of nerve root disorders are treated when possible.

For sudden, immediate pain, pain relievers (analgesics), such as acetaminophen and nonsteroidal anti-inflammatory drugs Nonopioid Analgesics In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more (NSAIDs), are used. If symptoms are not relieved, corticosteroids may be given by mouth or by injection into the space between the spine and the outer layer of tissue covering the spinal cord (called an epidural injection). However, with corticosteroids, pain relief tends to be modest and temporary.

For long-lasting (chronic) pain Chronic Pain Chronic pain is pain that lasts or recurs for months or years. Usually, pain is considered chronic if it does one of the following: Lasts for more than 3 months Lasts for more than 1 month after... read more , treatment can be difficult. Acetaminophen and NSAIDs are often only partly effective, and taking NSAIDs for a long time has substantial risks. Opioid pain relievers Opioid Analgesics In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more have a high risk of addiction. Some antidepressants Antidepressants In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more and antiseizure drugs Antiseizure drugs In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more , which are usually not considered pain relievers, can lessen pain due to nerve damage Neuropathic Pain Neuropathic pain is caused by damage to or dysfunction of the nerves, spinal cord, or brain. (See also Overview of Pain.) Neuropathic pain may result from Compression of a nerve—for example... read more . Physical therapy may also help relieve pain. If all of these treatments are ineffective, some people may wish to try alternative medicine (such as transdermal electrical nerve stimulation Nondrug Pain Treatments In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more , chiropractic Chiropractic In chiropractic, a manipulative and body-based practice, the relationship between the structure of the spine and the function of the nervous system is seen as key to maintaining or restoring... read more , acupuncture In some cases, treating the underlying disorder eliminates or minimizes the pain. For example, setting a broken bone in a cast or giving antibiotics for an infected joint helps reduce pain.... read more , or medicinal herbs Overview of Dietary Supplements Integrative medicine and health (IMH) and complementary and alternative medicine (CAM) include healing approaches and therapies that historically have not been included in conventional, mainstream... read more ).

If the pain is unrelenting or if pressure on spinal nerves is causing muscle weakness or loss of sensation, surgery to relieve the pressure may be necessary. If compression of the cauda equina or the spinal cord causes urinary or fecal incontinence, surgery is usually necessary to prevent permanent damage.

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