Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Nerve Root Disorders

(Radiculopathies)

By

Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Apr 2022
CLICK HERE FOR THE PROFESSIONAL VERSION
Topic Resources

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 information about such things as touch, pain, temperature, and vibration from the skin to the spinal cord.

Spinal roots come in pairs—one of each pair on each side of the body. There are 31 pairs:

  • 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.

  • In addition, 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.

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. Affected muscles may become 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, osteoarthritis, 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 identify which nerve roots are damaged and 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 and may do other tests depending on the suspected cause.

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 Pain Relievers Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most 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 Pain Relievers Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most pain... read more have a risk of addiction. Some antidepressants Antidepressants Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most pain... read more and antiseizure drugs Antiseizure drugs Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most 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 Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most 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 Nondrug Pain Treatments , or medicinal herbs Overview of Dietary Supplements Dietary supplements are used by about 75% of Americans. They are the most common therapies included among integrative medicine and health (IMH) and complementary and alternative medicine (CAM)... 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 and is done promptly to prevent permanent damage.

Drugs Mentioned In This Article

Generic Name Select Brand Names
TYLENOL
NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSIONAL VERSION
CLICK HERE FOR THE PROFESSIONAL VERSION
quiz link

Test your knowledge

Take a Quiz!
iOS ANDROID
iOS ANDROID
iOS ANDROID
TOP