A nerve root in the spine is the part of the nerve that branches off from the spinal cord and enters into the intervertebral foramen (bony opening between adjacent vertebrae). Most spinal levels have 4 total nerve roots with 2 on each side: the anterior (ventral) root carries motor signals from the brain out to the muscles, and the posterior (dorsal) root carries sensory signals from the skin to the brain. The anterior root and posterior root combine to form the spinal nerve, which exits the spinal canal through the intervertebral foramen.

The parts of the body innervated by a nerve root depend on its location. For example, a cervical nerve root is more likely to be involved with the arm, whereas a lumbar nerve root is more likely to be involved with the leg. Nerve roots help to innervate the side of the body where they are located.

Some medical professionals may refer to the nerve root as a spinal nerve or spinal nerve root. When discussing symptoms with a patient, doctors and other health professionals may simplify the language by referring to a single nerve root rather than 2 separate nerve roots, or by using the terms for nerve root and spinal nerve interchangeably.

When a nerve root becomes compressed or inflamed, it can cause pain, pins-and-needles tingling, numbness, and/or weakness to radiate out from the spine into another part of the body, such as the arm or leg.