brain, spinal cord, and nerve disorders
Nerve Root Disorders
Introduction
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 oracetaminophen) and corticosteroids. (See also Overview of the Peripheral Nervous System .) Nerve roots are the short branches of a Cranial nerves and spinal nerves . 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. 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. Themotor rootscarry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles. Thesensory rootscarry 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. 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. 