How Nerves are Injured

Nerve injury from a head injury, spinal cord injury, or neurological disease processes varies by the type of injury to nerves. The injury can occur in various aspects of the nerve and nerve transmission. Diseases or trauma may affect nerves differently.

The basic construction of a nerve has been identified and mapped out. A single nerve in the body consists of nerve fibers that are packaged together in bundles. Several nerve bundles are in every nerve. The outside layer of the nerve is covered in protein and fatty substances called myelin. This insulation of the nerve keeps messages (nerve impulses) flowing smoothly.

Nerves consist of three main parts: dendrites, a body, and an axon with an axon terminal. The cell body is a structure with a nucleus in the center of the body and short dendrites extending out of the body. It looks like a microscopic fried egg with branches coming off the edges. This is the powerhouse of the nerve. The cell body controls all the functions of the nerve.

Dendrites, or the small branches of the cell body, receive signals from other nerves. The dendrite collects signals which are interpreted by the cell body, and eventually to be moved along to other nerves.

The axon is one long branch that extends from the cell body. The axon carries messages from one nerve cell to another. This is the part that is covered in myelin. The axon terminal is at the opposite end of the nerve from the nerve body. It consists of shorter branches, much like those in the nerve body.

Messages are sent through nerves which are really chemical signals. Afferent nerves pick up signals from the skin and organs which are sent to the central nervous system (the brain and spinal cord). Efferent nerves carry messages from the central nervous system to the body. This process happens instantaneously or very, very quickly. For the process to be effective, each nerve must be functioning properly.

The brain and spinal cord make up the central nervous system. All the other nerves in the rest of the body make up the peripheral nervous system. Central nervous system nerves are the most protected from injury as they are safely stored within the skull and boney vertebrae of the spinal column. Peripheral nerves are protected by body tissue and muscles. However, damage to either set of nerves can occur, requiring different treatments. Results vary by individual.

Nerve injury occurs in three ways. A contusion (neuropraxia) or bump or bruise may happen by something pressing against the nerve. Crushing (axonotmesis) happens with extended pressure on the nerve. Transaction (neurotmesis) happens when the nerve is actually cut or severed.

Injury to any nerve in the central nervous system or peripheral nervous system can occur from overstretching or pulling them, either from a trauma such as hyperextending or hyperflexion anywhere along the spine. The nerves in the brain or spine can be compressed by a tumor, swelling, bleeding, or other medical issues. A bruise of the nerve, pressure on the nerve, or increased bleeding can arise from bumping the delicate nerve tissue, or a bone fragment pressed against the nerve. Other causes of pressure on the nerves in the central nervous system may include infection, inflammation, a shock wave from a blast or gunshot, electrocution, or a tumor. Ischemia, or lack of blood flow, can affect the function of a nerve by interrupting the blood supply to feed it. The nerve can be torn, which breaks the pathway for messages to be able to travel. Myelin can be damaged from trauma or disease, which does not allow messages to be transmitted effectively.

There are some diseases that can affect the nervous system. These include Alzheimer’s disease, motor neuron diseases such as ALS, multiple sclerosis, neurofibromatosis, and Parkinson’s disease, among others. Research to halt the progression of degenerative neurological diseases is extensive. Much of the research in the treatment of these diseases is applicable to all neurological research and repair. Expanding neurological research across diseases and injuries has provided improvements in all neurological studies.

Fortunately, in the brain or spinal cord, a complete transection of all the nerves rarely occurs because of the safety and security of the skull and spinal vertebrae. This means there is always a real possibility that the nervous system will be able to repair itself. The repair can be stimulated by therapeutic interventions to reduce swelling, surgery to remove an impingement on the nerve, such as a bone or blood pressing on the nerves, and therapy to stimulate function in the body.

In the peripheral nervous system, nerve transfers, grafting, and therapy can greatly assist in recovery. The peripheral nerves are capable of these treatments, whereas we are still learning about the use of these processes in the central nervous system. Nerves in the peripheral nervous system contain a type of cell called Schwann cells which particularly aids in regeneration.

The central nervous system recovers in a different way in that it has plasticity. This is a term used for the adaption of these nerves to seek alternative routes for message transmission. If a nerve channel is blocked for any reason in the central nervous system, messages being sent to and from the body will attempt to find alternative routes for communication. If you think about your central nervous system, sort of like your computer, you can see that the computer has various ways of doing one function. So does the central nervous system. For example, you may use your keyboard to copy/paste, use your mouse, or use function keys to accomplish the same goal. The central nervous system will attempt to find alternative ways to send messages.

Sometimes this process is more successful than other times. However, the central nervous system can be aided through various physical therapy methods as well as your own concentration and visualization. You can assist with the process by participating in therapeutic movement and thinking about the movement while it is occurring. For instance, if your toe is being moved, think about your toe moving. This sends a message from the toe being moved up to the brain at the same time, the thought process from the brain is being sent to the toe. The goal is to reconnect nerve transmission from above and below the injury.

Another help is to be perceptive about any messages you may be getting from your body. Some individuals will notice a ‘sensation’ of activity in the body, but it may not be as it was previously. Learning to realize the small perceptions of your body is key to learning how to harness the activity into functional gains.

Understanding the basic work and functions of nerves and how their treatment affects function provides a framework for how you can assist in your recovery. Using your mind to help guide the plasticity of your nervous system, as well as your body, can help aid in functional gain.

Pediatric Consideration:

Children will not have a grasp of how their nerves function, but you can assist them with participation in their recovery. Mention to them when you are moving their legs, arms, or body. This will give them a sense of what is occurring in their body on a fundamental level. They may recognize functions or sensations in the body that they may not be able to communicate to you but may automatically harness to their benefit.

Make movement a part of your child’s daily routine. Take time to play some moving games every day, as well as build movement into routine activities such as diaper changes or games for older children.