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.
Larry Gilman PhD, The Gale Group Inc., Gale, Detroit,