Pinched nerve

Definition

A pinched nerve is a general term that describes an injury to a nerve or group of nerves. The damage may include compression, constriction or stretching. Nerves that pass near or through bones or other rigid tissues are most susceptible to pinching. Pinched nerves result in numbness, pain, burning and tingling sensations radiating out from the affected area.

Description

Pinched nerves can be grouped into two types depending on where they occur in the body. Pinched nerves can occur within or in the vicinity of the vertebral column. For example, herniation of vertebral discs causes pain along the pathway of the nerve that is affected. Similarly, stenosis, or narrowing, of the vertebral column puts pressure on nerves traveling through the vertebrae. Another group of pinched nerves are referred to as nerve entrapment syndromes and they affect peripheral nerves, most commonly in the arms.

At least 80% of all herniated discs occur in people between the ages of 30 and 50. Between these ages, the tough outer core of the vertebral discs weakens and the soft gel-like inner core, which is under pressure, can more easily squeeze through weakened areas. After age 50, the inner core begins to harden, making herniation of discs less common. The amount of pain and discomfort resulting from a herniated disc varies depending on which disk has herniated and the amount of rupture. One of the most common problems associated with herniated discs is sciatica.

Nerve entrapment syndromes refer to a particular type of pinched nerve, in which peripheral nerves are chronically compressed resulting in pain or loss of function in an extremity. The most common nerve entrapment syndromes affect the median, ulnar and radial nerves of the arms. Nerve entrapment syndromes are extremely common, accounting for about 10–20% of all cases seen in neurosurgical practices. The most common entrapment syndrome is carpal tunnel syndrome. Cubital tunnel syndrome of the ulnar nerve, which runs down the arm and through the elbow, also occurs frequently.

Causes and symptoms

A nerve can be thought of as a wire encased in insulation that carries electrical information from one part of the body to another part. When the insulation or the wire itself becomes damaged the electrical signal does not move along the nerve efficiently or, in severe cases, the signal is not transmitted at all. The brain interprets this faulty transmission as pain, numbness or burning. Several different types of damage can occur to nerve cells that cause a disruption in the transfer of electrical signal. Compression or pressure on a nerve in one area will result in symptoms such as numbness or tingling in the region from which the nerve should be sending signals. The myelin sheath, which covers the nerve and is analogous to the insulation covering an electrical wire, can be damaged by scarring, in effect causing a short circuit of the nerve. Scar tissue hinders movement of a nerve in its tissue bed as the body moves and compromises the ability of the nerve to function properly, either by stressing the nerve fibers themselves or by impairing the blood supply to the nerve cell. Nerves can also be pulled or stretched, which constricts the nerve fibers. This is called a traction of the nerve and results in a decreased electrical flow through the nerve. The brain interprets the slow electrical signal as numbness, pain, or tingling.

Pinched Nerves in the Spine

Herniated discs are the most common reason for a pinched nerve along the vertebrae. This condition occurs when the gel-like core of a vertebral disc (nucleus puposus) ruptures through the tougher outer section (annulus) of the disc. The extrusion puts pressure on the adjacent nerve root causing it to function improperly. The discs that most often suffer from herniation are those in the cervical spine and the lumbar spine because they are the most flexible.

Lumbar disc herniations usually occur between lumbar segments 4 and 5, which cause pain in the L5 nerve, or between lumbar segment 5 and sacral segment 1, which cause pain on the S1 nerve. Pinching of the L5 nerve causes weakness in the big toe and ankle and pain on the top of the foot that may extend up to the buttocks. Pinching of the S1 nerve causes weakness in the ankle and numbness and pain in the sole and side of the foot. If the sciatic nerve, which runs from lumbar segment 3 down the vertebral column, is pinched by a herniation, the resulting condition is known as sciatica and it can cause pain, burning or tingling in the buttocks and leg. Lumbar disc herniations often heal on their own and conservative treatments are used to provide some relief from symptoms and to aid healing. Such treatments include physical therapy, chiropractic manipulations, non-steroidal anti-inflammatory drugs, oral steroids and, in some cases, an injection of a steroid such as cortisone. In more severe cases, surgery to remove the pressure of the disc from the nerve is warranted. This is most often performed using microsurgical techniques.

Cervical disc herniations occur less frequently than lumbar disc herniations because there is less force in the cervical spine and less disc material between vertebrae. When nerve roots exiting the cervical spine are pinched, they can cause a radiculopathy, ora pain in the arm. Rarely, the nerves between the first and second or second and third cervical segments can be pinched. These nerves are sensory nerves and can cause chronic headaches. Usually cervical disc herniations heal on their own and conservative treatments are used to relieve symptoms and pain. These treatments include rest, non-steroidal anti-inflammatory drugs, physical therapy, chiropractic treatments and manual traction. Epidural injections of cortisone may also help relieve pain. Surgical techniques can also be used to remove the herniated disc from impinging on nerves.

Stenosis, or narrowing, of the spinal canal can cause a pinching of the spinal cord. This occurs commonly with age and may cause weakening of muscles or loss of coordination. Often symptoms develop slowly and worsen over a long period of time. Usually treatment for this condition requires surgery to relieve pressure on the spinal canal.

Nerve Entrapment Syndromes

Most nerve entrapment syndromes are caused by injury to the nerve as it travels between a canal consisting of bone or ligament. One side of the canal is able to move so that the injury is aggravated by repetitive rubbing or slapping against the edges of the canal. Rest and splinting are therefore effective treatments for entrapment syndromes. Symptoms of entrapment syndromes usually proceed from pain and numbness to weakness and muscle atrophy.

The most common nerve entrapment syndrome is carpal tunnel syndrome (CTS), with a reported occurrence between 1–10% of the population. Statistics indicate that nearly half of a million surgeries for CTS are performed yearly. It occurs most often in people who perform repetitive motions with their hands, such as bankers, computer operators, secretaries, grocery store workers and bank tellers.

The carpal tunnel is in the wrist of the hand. It is bound on the palm side by the transverse carpal tunnel ligament which attaches to the four carpal tunnel bones that extend around the back of the wrist. The inside of the carpal tunnel houses ten flexor tendons, which are used to bend fingers, as well as the median nerve and the ulnar nerve. The median nerve, which is aggravated in CTS, is between the transverse carpal tunnel ligament and the flexor tendons. When the hand moves, the flexor tendons may glide back and forth through the carpal tunnel up to .75 in (2 cm) in either direction. These tendons are covered in a substance called tenosynovium that allows them to move easily. When the tendons move rapidly, the tenosynovium may heat up and expand, putting pressure on the median nerve. This pressure results in pain and tingling in the thumb, index finger, middle finger and along the thumb side of the fourth finger. Symptoms may also include a dull, aching pain in the wrist, extending up to the elbow. Most people suffering from CTS find that the pain worsens at night and they will awaken with numbness in the middle fingers and thumb. Both bending the wrist and extending the wrist cause increased pain. Given time, CTS may continue to aggravate the median nerve, resulting in scar tissue that only enhances the syndrome.

CTS is usually treated with conservative treatments including rest and splinting of the wrist, especially at night. Using non-steriodal anti-inflammatory medications may relieve some of the swelling in the carpal tunnel. Injections of cortisone into the carpal tunnel are also effective at relieving swelling. Surgery can also be used in severe cases to relieve pressure on the median nerve.

Ulnar nerve entrapment syndrome occurs when the ulnar nerve is injured. The ulnar nerve extends down the arm and into the hand, enervating the ring finger and the little finger. In the elbow, it passes through a tunnel called the cubital tunnel. Most ulnar nerve entrapments occur in the cubital tunnel, although some can occur at the wrist. Most commonly, trauma to the elbow or repetitive bending of the elbow puts pressure on the ulnar nerve that damages the myelin sheath insulating and protecting the nerve. Symptoms include tenderness on the inside of the elbow, numbness in the hand especially the ring and little fingers and decreased coordination and strength in the hand. Conservative treatments for ulnar nerve entrapment include rest and splinting of the elbow and corticosteroids to reduce pain. In severe cases, surgery to move the ulnar nerve from behind the elbow to the front of the elbow relieves the pressure on the nerve.

Suprascapular nerve entrapment is a rare type of entrapment syndrome that most often occurs in athletes. The major symptom is a dull pain near the shoulder blade, which can progress to weakness and muscle atrophy. The pain is not localized, but does not extend to the neck or arm.

Tarsal tunnel syndrome is another uncommon type of nerve entrapment syndrome that causes burning, tingling and pain in the plantar surface of the foot. Bending of the ankle worsens the pain and there is a weakening of muscles in the big toe.

Resources

BOOKS

Beers, Mark H., ed. Merk Manual of Medical Information. Merk Research Laboratories, 2003.

Fried, Scott M. Light at the End of the Carpal Tunnel: A Guide to Understanding and Relief from the Pain of Nerve Problems. Healing Books, 1998.

Tierney, Lawrence M., Stephen J. McPhee, and Maxine A. Papadakis, eds. Current Medical Diagnosis and Treatment. McGraw-Hill, 2003.

OTHER

Hochschuler, Stephen H. "What You Need to Know about Sciatica." SpineHealth.com. (September 22, 2003). http://www.spine-health.com/topics/cd/d_sciatica/sc01.html.

Luskin, Brandon. "Pinched Nerve—What Is It?" SpineUniverse.com. (November 24, 2003). http://www.spineuniverse.com/displayarticle.php/article232.html.

National Institute of Neurological Disorders and Stroke. Pinched Nerve Information Page. (July 1, 2001). http://www.ninds.nih.gov/health_and_medical/disorders/pinchednerve.htm.

Pang, Dachling, and Kamran Sahrakar. "Nerve Entrapment Syndromes." Emedicine. (October 4, 2001). http://www.emedicine.com/med/topic2909.htm.

Ullrich Jr., Peter F. "Cervical Disc Herniation." SpineHealth.com. (July 2001). http://www.spinehealth.com/topics/cd/overview/cervical/cerv01.html.

Ullrich Jr., Peter F. "Lumbar Disc Herniation." SpineHealth.com. (March 15, 2001). http://www.spine-health.com/topics/cd/overview/lumbar/young/lum01.html.

"Ulnar Nerve Entrapment." American Academy of Orthopaedic Surgeons. (November 2000). http://www.orthoinfo.org/fact/thr_report.cfm?Thread_ID=143&topcategory=Arm.

ORGANIZATIONS

National Rehabilitation Information Center (NARIC). 4200 Forbes Boulevard Suite 202, Lanham, MD 20706-4829. (301) 562-2400 or (800) 346-2742; Fax: (301) 5 62-2401. naricinfo@heitechservices.com. http://www.naric.com.

Juli M. Berwald, PhD

Definition

A pinched nerve is caused by some anatomical structure putting pressure on a nerve and impairing its function. This problem may occur in many different areas of the body. The most common places are those in which a nerve must travel through a small space. Examples include the region where the nerve roots exit the spine called the intervertebral foramen, and the carpal tunnel at the wrist, where a nerve must travel through a tunnel created by the wrist bones and ligaments.

Description

A pinched nerve may go by several different names. It may be called nerve compression, entrapment, or impingement. Many problems involving pinched nerves will be called syndromes. Examples include carpal tunnel syndrome, thoracic outlet syndrome, and piriformis syndrome. If the nerve is pinched right near its root where it attaches to the spinal cord it is often called a radiculopathy.

The nerves that exit the spine and go down the upper limb and lower limb are gathered together in groups. Each group of nerves is called a plexus. In the neck region the nerves that leave the neck and go down the upper arm make up the brachial plexus. In the low back region, the nerves that go down the leg may come from the lumbar plexus or the sacral plexus. If a nerve is pinched where it is part of a plexus, it may be called a plexopathy. If the nerve is pinched farther along its length after it has left the plexus it is called a neuropathy.

A nerve is responsible for carrying two different types of signals. It carries sensory information, such as sensations of heat, pressure, texture, pain, or body position back to the spinal cord where that information will eventually be transmitted directly to the brain. These sensory signals that travel through the nerves are called afferent signals. A nerve also carries motor signals from the brain and spinal cord that tell the muscles when and how much to contract in order to create movement in the body. These motor signals that go from the brain and spinal cord out to the muscles are called efferent signals. When a nerve is pinched it may cause dysfunction with either the sensory (afferent) or motor (efferent) signals.

Causes & Symptoms

A pinched nerve may occur from a direct blow. Most people are familiar with this sensation when they bang their elbow on a hard surface and get a sharp pain or prickling sensation down the arm. The symptoms of this kind of pinched nerve are usually very short-lived and are not a significant problem unless the force of the impact was severe.

What is much more common is the sensation of small amounts of pressure on the nerve from such adjacent structures as bones, muscles, tendons, and ligaments. This pressure most often occurs when the nerve has to travel through a small space between these structures. The nerve may get compressed with a small amount of pressure for a long period of time. It is the long time period of pressure on the nerve that causes the most damage. In many cases these long periods of pressure are related to the person's job. Occupations in which a person must hold the wrist, forearm or shoulder in one position for long periods of time and/or perform repetitive movements have a high rate of workers with pinched nerve syndromes. Dental hygienists, keyboard instrumentalists, violinists, data entry workers, assembly line and construction workers, and professional athletes are examples of workers at risk for pinched nerve syndromes.

When pressure is placed on the nerve a person may feel a variety of different symptoms. Paresthesia (the sensation of pins and needles) is often felt first. The sensations of paresthesia are usually felt anywhere along the nerve from the site of compression toward the far end of the extremity. Symptoms may also go from the site of compression toward the spinal cord, but it is not as common. In addition to paresthesia sensations, a person with a pinched nerve may also feel sharp, shooting pain, or pain that feels like an electrical shock going down the extremity. All of these symptoms are from impairment of the afferent (sensory) nerve signal transmission. The sensation is not necessarily near the area where the pressure is occurring.

Motor (efferent) signals can also be impaired from nerve compression. This will most likely show up as muscle weakness or problems with coordination. For example, people with carpal tunnel syndrome will frequently report losing grip strength. This is because the nerve has been compressed and signals are not getting through to the muscles of the hand that produce the grip.

Diagnosis

Most pinched nerve conditions can be diagnosed with physical examination. The practitioner will take a thorough history, including an occupational history, and investigate the nature of the signs and symptoms to see if they indicate the likelihood of nerve compression. A number of physical examination tests may also be performed to see if nerve compression is aggravated with specific movements or pressure in certain areas. In addition to physical examination and information from the patient's history, nerve conduction tests may be run to see if the nerves are transmitting signals at the proper rate. If a nerve compression problem exists, there will be a slowing in the velocity of signal transmission in that nerve and it will likely be detected by the nerve conduction velocity test.

As of 2003, diagnostic imaging is being increasingly used to aid in the diagnosis of nerve entrapment and compression syndromes. Recent refinements in ultrasound and magnetic resonance imaging (MRI) provide doctors with detailed pictures of the anatomy of peripheral nerves and the changes that take place in them with compression syndromes.

Treatment

Alternative therapy practitioners who specialize in such manual therapy methods as chiropractic, osteopathy, or massage therapy will look closely at the mechanical factors in the region of pain to identify what is pinching the nerve. If it is determined that the nerve is being compressed by some structure like a muscle that is pressing on the nerve, then therapy will be aimed at reducing tightness in that muscle so that it no longer presses on the nerve. This will generally be done through a variety of soft tissue therapy methods. In some instances there are other postural or mechanical distortions that may lead to nerve compression, and those will be addressed through manual therapy or various movement retraining methods.

Treatment will also focus on changing mechanical factors that may have led to nerve compression. For example, in carpal tunnel syndrome it is often some repetitive use activity that has led to the problem. If that activity can be altered so there is not an accumulation of stress on the soft tissues, it is likely that the symptoms of the nerve compression will be resolved. However, nerve compression symptoms may be slow to fully resolve even after the primary cause of the compression has been addressed.

Acupuncture can be quite helpful in treating pinched nerves since it has been shown to be a very effective method for producing pain relief. The primary goals of an acupuncture treatment will be both to reduce pain sensations and to get proper energy moving along the pathways that have been impaired. Needles will be inserted in areas that will help encourage proper neurological flow through the involved area. Acupuncture with electrical stimulation of the needles may also be used for treating pinched nerves.

In addition to acupuncture, other approaches from traditional Chinese medicine may be used. Both topical and oral herbal preparations may be used to help restore proper function and address any underlying causes of the pinched nerve symptoms. Cupping may be used to help free soft tissue restrictions that may be compressing the nerve structures in the area.

Allopathic Treatment

Traditional allopathic treatment for pinched nerves will also focus on the site of nerve compression and try to manage the symptoms first through conservative therapy. Oral medications may be given to relieve pain or reduce any inflammation that may be contributing to the nerve compression. Physical therapy may be used to help address any mechanical factors that may be contributing to the nerve compression. Physical therapy approaches are likely to include stretching, joint mobilization, soft tissue treatments, or such other modalities as ultrasound to address the causative factors of the nerve compression. Splinting is an additional conservative approach to nerve compression syndromes.

Depending on where the nerve compression is located, surgical treatment may sometimes be necessary. Surgery is often performed for such common nerve compression problems as carpal tunnel syndrome and thoracic outlet syndrome. Most of these surgical procedures will be aimed at relieving pressure on the affected nerve.

Some newer allopathic treatments that are used to relieve the pain of pinched nerve syndromes include low-level laser therapy (LLLT) and transcutaneous electrical nerve stimulation (TENS). In LLLT, a continuous-wave red-beam laser is aimed at acupuncture points on the affected area. In TENS, the affected nerve is stimulated with high-frequency electrical signals, which disrupt the transmission of pain impulses along the nerve so that the pain is no longer felt. Both these approaches give good results in treating pinched nerve syndromes, as they are noninvasive and painless.

In some cases in which the pinched nerve is related to the patient's job, a change of occupation may be necessary.

Expected Results

Most problems with pinched nerves will be resolved as soon the pressure on them is released. If the symptoms have been present for a long time, the relief of the condition may not be immediate. The longer the pressure has been applied, the longer it is likely to take for the symptoms to be resolved.

Prevention

Most pinched nerve conditions can be avoided with proper body mechanics. Repetitive motions of the upper extremity are notorious for causing pinched nerves in several places, and it is wise to make sure a person is conditioned for the level of activity he or she is engaging in so as to prevent this from occurring. The individual should also be careful of activities that might put pressure on nerves for long periods. For example, nerves can be compressed in the shoulder region from the wearing of heavy backpacks or handbags for long periods.

Resources

Books

Beinfield, H. Between Heaven & Earth: A guide to Chinese Medicine New York: Ballantine, 1991.

Butler, D. Mobilisation of the Nervous System. London: Churchill Livingstone, 1999.

Dawson, D., M. Hallet, and A. Wilbourn. Entrapment Neuropathies. Philadelphia: Lippincott-Raven, 1999.

Hammer, W. Functional Soft Tissue Examination and Treatment by Manual Methods, Second Ed. Gaithersburg, MD: Aspen, 1999.

Maciocia, G. Foundations of Chinese Medicine. London: Churchill Livingstone, 1989.

Stux, G. Basics of Acupuncture. New York: Springer-Verlag, 1991.

Periodicals

Anton, D., J. Rosecrance, L. Merlino, and T. Cook. "Prevalence of Musculoskeletal Symptoms and Carpal Tunnel Syndrome Among Dental Hygienists." American Journal of Industrial Medicine 42 (September 2002): 248-257.

Becker, J., D. B. Nora, I. Gomes, et al. "An Evaluation of Gender, Obesity, Age and Diabetes Mellitus as Risk Factors for Carpal Tunnel Syndrome." Clinical Neurophysiology 113 (September 2002): 1429-1434.

Gerritsen, A. A., H. C. de Vet, R. J. Scholten, et al. "Splinting vs Surgery in the Treatment of Carpal Tunnel Syndrome: A Randomized Controlled Trial." Journal of the AmericanMedical Association 288 (September 11, 2002): 1245-1251.

Naeser, M. A., K. A. Hahn, B. E. Lieberman, and K. F. Branco. "Carpal Tunnel Syndrome Pain Treated with Low-Level Laser and Microamperes Transcutaneous Electric Nerve Stimulation: A Controlled Study." Archives of Physical Medicine and Rehabilitation 83 (July 2002): 978-988.

Nathan, P. A., K. D. Meadows, and J. A. Istvan. "Predictors of Carpal Tunnel Syndrome: An 11-Year Study of Industrial Workers." Journal of Hand Surgery 27 (July 2002): 644-651.

Roquelaure, Y., J. Mariel, S. Fanello, et al. "Active Epidemiological Surveillance of Musculoskeletal Disorders in a Shoe Factory." Occupational and Environmental Medicine 59 (July 2002): 452-458.

Spratt, J. D., A. J. Stanley, A. J. Grainger, et al. "The Role of Diagnostic Radiology in Compressive and Entrapment Neuropathies." European Radiology 12 (September 2002): 2352-2364.

Werner, R. A., and M. Andary. "Carpal Tunnel Syndrome: Pathophysiology and Clinical Neurophysiology." Clinical Neurophysiology 113 (September 2002): 1373-1381.

Organizations

American Academy of Medical Acupuncture (AAMA). 4929 Wilshire Blvd., Suite 428, Los Angeles, CA 90010. (323) 937-5514. .

American College of Occupational and Environmental Medicine (ACOEM). 1114 North Arlington Heights Road, Arlington Heights, IL 60004. (847) 818-1800. .

American Physical Therapy Association (APTA). 1111 North Fairfax Street, Alexandria, VA 22314. (703)684-APTA or (800) 999-2782. .

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health (NIOSH). (800) 35-NIOSH. Fax: (513) 533-8573. .

[Article by: Whitney Lowe; Rebecca J. Frey, PhD]