Trauma is the response to a deeply distressing or disturbing event that overwhelms an individual’s ability to cope, causes feelings of helplessness, diminishes their sense of self and their ability to feel a full range of emotions and experiences.

It does not discriminate and it is pervasive throughout the world. A World Mental Health survey conducted by the World Health Organization found that at least a third of the more than 125,000 people surveyed in 26 different countries had experienced trauma. That number rose to 70% when the group was limited to people experiencing core disorders as defined by the DSM-IV (the classification found in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition). But those numbers are just for instances that have been reported; the actual number is probably much, much higher.

Injury, also known as physical trauma, is damage to the body caused by an external force. This may be caused by accidents, falls, hits, weapons, and other causes. Major trauma is injury that has the potential to cause prolonged disability or death. In 2013, 4.8 million people world-wide died from injuries, up from 4.3 million in 1990. More than 30% of these deaths were transport-related injuries. In 2013, 367,000 children under the age of five died from injuries, down from 766,000 in 1990. Injuries are the cause of 9% of all deaths, and are the sixth-leading cause of death in the world.

Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve fiber injury and whether there is continuity of the nerve. Usually, however, (peripheral) nerve injury is classified in five stages, based on the extent of damage to both the nerve and the surrounding connective tissue, since supporting glial cells may be involved.

Unlike in the central nervous system, neuroregeneration in the peripheral nervous system is possible.The processes that occur in peripheral regeneration can be divided into the following major events: Wallerian degeneration, axon regeneration/growth, and nerve reinnervation. The events that occur in peripheral regeneration occur with respect to the axis of the nerve injury. The proximal stump refers to the end of the injured neuron that is still attached to the neuron cell body; it is the part that regenerates. The distal stump refers to the end of the injured neuron that is still attached to the end of the axon; it is the part of the neuron that will degenerate, but the stump remains capable of regenerating its axons.