Nerves form the central nervous system and are involved in conducting messages from the brain to other parts of the body. They are of two types – motor, which help in movement and sensory, which lets us sense pressure, temperature and pain. Many nerve fibers are grouped together to form a bundle and are protected by an insulating cover.
Messages in the form of electric pulses pass through nerves, to and from the brain, through cells called neurons. Neurons are made up of 3 parts: a cell body, a long tube-like axon which transmits signals to the next nerve cells and dendrites that receive signals from other neurons.
Nerves are fragile and can get easily injured by stretching, pressure, or laceration. Injury can involve only the nerve or the outer protective covering as well, which obstructs the transmission of messages to and from the brain. This stops the muscles from moving the affected part of the body and sensations from being felt in the part supplied by the damaged nerve.
Nerve conduction velocity (NCV) and electromyography (EMG) tests help evaluate the transmission of electric currents through the nerves. Imaging tests, including CT scans, MRI and MRI neurography, also help identify the extent of injury. Nerve injury can be classified into five types:
- First-degree injury blocks message transmission locally and is reversible, usually recovering within hours to a few weeks
- Second-degree injury involves a loss of continuity in axons
- Third-degree injury damages axons and their supporting structures
- Fourth-degree injury harms axons and surrounding tissues, creating scars that prevent regeneration of the nerve
- Fifth-degree injuries usually involve tearing or severe stretching where the nerve is separated into two
Nerve injuries can be treated with medication and conservative treatments including rehabilitation, physical and massage therapy, acupuncture, orthotics, and weight loss management. Surgery may include a simple cleaning of the nerve (neurolysis) or grafting when the tests show that there is passage of electric signals through them.