Radiculopathy refers to disease of the spinal nerve roots (from the Latin radix for root). Radiculopathy produces pain, numbness, or weakness radiating from the spine.
At the joints between the vertebrae, sensory nerves (nerves conducting sensory information toward the central nervous system) and motor nerves (nerves conducting commands to muscles away from the central nervous system) connect to the spinal cord. Each spinal nerve divides or fans out just before merging with the spinal cord. These smaller, separate nerve bundles are termed the roots of the nerve because they are reminiscent of the way the roots of a plant divide in the ground.
Damage to the spinal nerve roots can lead to pain, numbness, weakness, and paresthesia (abnormal sensations in the absence of stimuli) in the limbs or trunk. Pain may be felt in a region corresponding to a dermatome, an area of skin innervated by the sensory fibers of a given spinal nerve or a dynatome, an area in which pain is felt when a given spinal nerve is irritated. Dynatomes and dermatomes may overlap, but do not necessarily coincide.
Radiculopathies are categorized according to which part of the spinal cord is affected. Thus, there are cervical (neck), thoracic (middle back), and lumbar (lower back) radiculopathies. Lumbar radiculopathy is also known a sciatica. Radiculopathies may be further categorized by what vertebrae they are associated with. For example, radiculopathy of the nerve roots at the level of the seventh cervical vertebra is termed C7 radiculopathy; at the level of the fifth cervical vertebra, C5 radiculopathy; at the level of the first thoracic vertebra, T1 radiculopathy; and so on.
Radiculopathy is to be distinguished from myelopathy, which involves pathological changes in or functional problems with the spinal cord itself rather than the nerve roots. Sometimes, radiculopathy is also distinguished from radiculitis, the latter being defined as irritation (hence the "itis" suffix) of a nerve root that causes pain in the dermatome or dynatome corresponding to that nerve. Radiculopathy, on the other hand, denotes spinal nerve dysfunction (not just irritation) presenting with pain, altered reflex, weakness, and nerve-conduction abnormalities. Pain may not be present with radiculopathy, but is always present with radiculitis.
Millions of persons experience some form of radiculopathy at some point in their lives. Because many of the causes of radiculopathy are long-term diseases (e.g., ankylosing spondylosis, diabetes) or diseases that tend to affect the elderly (e.g., arthritis), radiculopathy occurs more often in the middle-aged and elderly than in the young. However, injuries due to sports, heavy lifting, or bad posture affect the young as well. Cervical disc herniation with radiculopathy (mostly involving the C4 to C5 levels) affects 5.5 per 100,000 adults every year, with the highest risk being for adults 35 to 55 years year old.
Radiculopathy can be caused by any disease or injury process that compresses or otherwise injures the spinal nerve roots. Violent blows or falls, cancer, some infections such as flu and Lyme disease, diseases that lead to degeneration of the vertebrae and/or intervertrebral discs (osteoarthritis), slipped or herniated discs, scoliosis, and other factors can cause radiculopathy. For example, extreme backward bending of the neck can trigger cervical radiculopathy. This has given rise to a recently-recognized category of radiculopathy termed "salon sink radiculopathy," so-called because salon patrons are asked to tip their heads sharply backward into sinks for shampooing. Spondylosis (immobilization and growing-together of one or more vertebral joints, often due to osteoarthritis) can deform the structures of bone, cartilage, and ligament through which spinal nerves must pass, leading to cervical and lumbar radiculopathy. Thoracic and lumbar radiculopathies are a common result of diabetes, which can impair blood flow to the spinal nerve roots.
Radiculopathy is a possible diagnosis when numbness, pain, weakness, or paresthesia of the extremities or torso are reported by a patient, especially in a dermatomal pattern. However, these symptoms can also be caused by nerve compression remote from the spine, and the physician must rule out this possibility before ruling in favor of radiculopathy. Electrodiagnostic studies can help distinguish radiculopathy from other diagnoses. These techniques include current perception threshold testing, which tests patient ability to sense alternating electric currents at several frequencies; electromyographic nerve conduction tests; and testing of sensory evoked potentials (changes in brain waves in response to sensory stimuli).
When radiculopathy is diagnosed, the location of the affected nerve roots and, ultimately, the cause of their dysfunction must be determined. Diagnosticians look at the precise features of radicular symptoms in order to determine the spinal level of the affected root or roots. For example, radiculopathy at the C7 level (the nerve root most often affected by herniated cervical disc) is characterized by weak triceps and wrist extensor muscles and a numb middle finger. Radiculopathy at the L3 (third lumbar disc) level is characterized by decreased patellar (kneecap) reflex, loss of sensation and/or pain in the anterior (forward) part of the thigh, and weakness in quadriceps muscle; and so on.
X ray or MRI may be used to confirm the diagnosis. A herniated disc, for example, will be revealed by imaging. A herniated disc is one that has partly popped or bulged out from between the vertebra above and below it. This may place pressure on the nerve roots and on the spinal cord itself.
In persons with spinal cancer or other progressive disorders, the appearance of radiculopathy may be an important sign that pressure is beginning to be exerted by the tumor or some other changing structure. This may signal that it is time for surgical intervention.
Diagnosis of radiculopathy will usually involve a neurologist. An orthopedist will usually be involved as well. Other specialists will be required depending on the cause of the radiculopathy (e.g., oncologist, if cancer is present). Treatment will usually call for a physical therapist. An orthopedic surgeon would perform any necessary surgery.
Treatment for radiculopathy varies with the nature and severity of the disease process or injury that has caused the disorder. Conservative (non-surgical) treatment is often attempted first. This consists primarily of rest, exercise, and medication. Patient-specific exercises are prescribed by a physical therapist for the targeted strengthening of muscles and other supporting tissues to relieve pressure on affected spinal nerve roots. Weight loss may be advised to decrease stress on the spine. Medications may include oral opioids (e.g., morphine) or other analgesic (anti-pain) medications. In severe cases, injection of an opioid by an external or implanted pump directly into the affected area may be prescribed. Epidural corticosteroid injections, selective nerve root block, and epidural lysis (destruction) of adhesions are also used to treat radiculopathy. A soft neck collar may be prescribed for persons with cervical radiculopathy.
When conservative treatment fails, surgery may be necessary. The primary purpose of surgery is to take pressure off of affected nerve roots or the blood vessels that serve them and to stabilize spinal structure, but surgery may also sever nerves in order to relieve severe pain. Fusion of vertebrae (i.e., removal of the flexible intervertebral disc and joining of the adjacent vertebrae so that they grow into a single bone) was for many decades a common treatment for intractable radiculopathy, but as of 2003, a novel implant, the Bryan disc, was under study by the US Food and Drug Administration. The Bryan disc is a flexible disc or ring of titanium and Teflon that is used to replace the intervertebral disc in patients with degenerative disc disease. Two versions of the disc, one cervical (for the neck) and the other lumbar (for the lower back) were under development. Early reports from surgeons were positive. The advantage of such an implant over fusion is that the patient does not lose flexibility in that part of their spine.
Exercise is key to the treatment of both conservative and surgical treatment of radiculopathy. It may even be curative in some cases. It is also an important aspect of recovery from surgery. Exercise is done as directed by a physical therapist.
As of mid-2004, a clinical trial sponsored by the National Institute of Dental and Craniofacial Research was recruiting participants. The goal of this clinical trial was to evaluate the effectiveness of two drugs (i.e., nortriptyline and MS Contin, a type of morphine) in treating lumbar radiculopathy, also known as sciatica. This was a phase II clinical trial, meaning that it involved a medium-size group (100–300 participants) to evaluate effectiveness and side effects of the treatment. Persons interested in participating should contact the Patient Recruitment and Public Liaison Office at telephone (800) 411-1222, or e-mail at: firstname.lastname@example.org.
Prognosis varies with the underlying process causing the radiculopathy. For sports injuries, at one extreme, the prognosis is excellent; for degenerative disc disorders, even surgery may not completely or permanently resolve the problem. However, new surgical techniques are improving this picture.
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National Institute for Neurological Diseases and Stroke (NINDS). 6001 Executive Boulevard, Bethesda, MD 20892. (301) 496-5751 or (800) 352-9424. <http://www.ninds.nih.gov>.
Larry Gilman, PhD