NeuroBiology and Behavior
April 7th, 1998
Spinal cord injury is a serious problem that effects close to 250,000 people in the United States with 10,000 people being injured per year . There are many things that can lead to spinal cord injury, including athletic injuries, car accidents, and recreational activities like swimming and biking. It primarily effects those between the ages of 16 and 30 and drastically effects the rest of their lives. It is a very debilitating injury that requires extensive medical care, often leaves the patients in a great deal of pain for the rest of their lives(2), and the treatment of which costs $10 billion dollars a year in the US.(facts from site 1) With all of these factors spurring research on there is a strong drive to find a cure for such a devastating injury.
Spinal cord injuries can happen anywhere along the spinal cord, but the exact location of the trauma determines the effects that the injury will have. Injuries in the lower back, between the Sacrum(S1-S5) and Lumbar(L1-L5) vertebrae mainly effect the legs. Breaks in the Thoracic(T1-T12) vertebrae, located in the middle of the back, effect the torso and portions of the arms. While injuries in the spine above the shoulder blades, the Cervical(C1-C8) vertebrae, effect not only movement in the neck, but functions such as breathing, speaking, and eating. In the past, some functions have been able to be regained by some individuals, but after the initial recovery period most people see little improvement over the course of their lives.
The main reason for such a poor recovery is that the nerve cells in the spinal cord do not regenerate on their own. Once the spinal cord develops, two things keep it from growing. One of which is an inhibitor protein and the other is lack of growth factors. One of the reasons of this lack of growth could be due to the complex nature of the spinal cord. Once the nervous system infrastructure is established and connections are made, the body would want to keep them constant. If they were to constantly be changing then our bodies would have a difficult time communicating within itself. The other factor in favor of limited growth is the lack of physical space within the spinal cord. If nerve cells kept growing they would quickly run out of space and that would create all kinds of new problems.
The limited space within the vertebrae actually plays an important roll in spinal cord injury. Once the initial injury occurs the body, as with every other part of the body, tries to protect the injured area with swelling. But the swelling occurs within the small confines of the spinal column and causes further damage to the surrounding tissue. It has only recently been discovered how much of an impact this secondary damage has. One of the areas of crucial ongoing research is on what kind of window of opportunity medicine has in treating these types of injuries and still attaining the best recovery.
There have also been breakthroughs in stimulating nerve re-growth by Dr. Martin Schwab at the University of Zurich in Switzerland. He has been able to create an antibody, called IN-1, that combats the inhibitory proteins which prevent nerve growth. Using IN-1 with naturally occurring nerve growth factors, NT-3, he was able to produce promising results, with rats regaining some function where there was no function before.(1) Although I'm excited for this progress in synthetic control, I'm curious to know why we need to synthesize something instead of attempting to mimic the natural process. It's possible that this new antibody is based on what the body uses during initial nerve growth, but in some ways it seems easier to try an initiate a process that already exists instead of creating a new one with some new components.
But the regeneration of nerve cells is not the only step in the process of recovery that must be solved. Recovery also has to include the regeneration of the Schwann cells that help nourish the nerve cells and the myelin that insulates the axons in order for them to send signals. Without these two components new nerve cells would be useless. Scientists are experimenting with techniques to solve this problem, including the injection of Schwann cells to compensate for their absence in the effected area(3). They have also experimented with placing the spinal cords from fetal rats into injured rats and have met with some success(3).
The next step in the recovery process, once the actual connections are reestablished is rehabilitation, learning how to use the new connections. So far there have only been reports of partial recovery in lab animals and I wonder if that is due to a random nature in the reconnection of the nerve cells. I would have to agree that presently the most important step is reconnection, but in the future science will have to deal with either making the best of the connections that are created or creating a way to guide the connections back into their previous network.
Although the area of spinal cord injury has been very bleak in the past, major hurdles have been overcome and science is now working on a way to help people recover from their injuries instead of teaching them how to live with them.
Web Sites used in this Paper
(1) Welcome to the American Paralysis Association - APACURE.COM
-This site contains a short video on axon degeneration and an animated illustrations on the process of death and regeneration in nerve cells.
(2) Theories on the Effects of Acupuncture on the Nervous System
Emma Christensen, [deals with concepts of pain]
(3) Spinal Cord Injury - - Research Highlights
(4) Spinal Cord Injury Center
THE FACTS ON SPINAL CORD INJURY(1)
Sources: American Paralysis Association, The University of Alabama National Spinal Cord Injury Statistical Center, The Dana Alliance for Brain Initiatives and Paralyzed Veterans of America.