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86 m a s s a g e & b o d y w o r k m a r c h / a p r i l 2 0 1 7 technique SCIENCE OF NERVES Deciphering Nerve Injuries By Whitney Lowe One of the most challenging situations facing practitioners who work with pain and injury conditions is correctly interpreting nerve injury symptoms. It seems that in many massage therapy training programs, the nervous system gets only cursory attention, yet pain originating in the nervous system is a critical factor that drives people to our practices. The key to understanding nerve injury lies in a solid grounding of the structure and function of these crucial nerve tissues throughout the body. Let's explore these tissues moving from the center out to the periphery and how various injuries or dysfunctions affect these tissues. The brain and spinal cord make up the central nervous system. The nerves that exit the spinal cord and permeate the entire body make up the peripheral nervous system. It is the peripheral nervous system that is of greatest concern to massage therapists as the cause for many pain complaints. NERVE ROOT LEVEL There are two sets of nerve fibers that connect with the spinal cord on each side. Fibers from the dorsal root enter the spinal cord toward the posterior side, while fibers in the ventral root exit the spinal cord on their way to the periphery (Image 1). The dorsal nerve root contains sensory fibers bringing all the body's sensory information back to the spinal cord on the way to the brain. The ventral roots contain motor fibers for sending signals from the central nervous system out to various target tissues, such as the muscles. Just distal to the spinal cord, the nerve fibers bundled within the dorsal root and the ventral root join together, encased in a single bundle. The bundle at that particular spinal level is generally referred to as the nerve root. For example, the nerve root that exits just below the L4 lumbar vertebra is referred to as the L4 nerve root (Image 2). FORMATION OF PERIPHERAL NERVES Moving distally, nerve roots join with fibers from other nearby nerve roots. At this level, the connection of nerve fibers is referred to as a plexus (Image 3). There are four major nerve plexuses with nerve roots that exit the spinal cord. The most superior is the cervical plexus. It is composed of nerve roots from the C1 to C4 level. The nerves that form out of the cervical plexus remain in the cranium and cervical region. Nerve roots in the C5 to T1 level make up the brachial plexus. Nerves that eventually form out of the brachial plexus contain branches that terminate in the neck or shoulder, or extend down the entire length of the upper extremity. The brachial plexus is routinely involved in various pain and injury conditions because it is easily exposed to adverse forces due to its location in the neck. Dorsal and ventral nerve roots. L4 nerve root level. 1 2 Vertebral body Ventral (motor) branch Dorsal (sensory) branch L4 vertebra L4 nerve root