This Happens After a Spinal Cord Injury


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A spinal cord injury resembles a natural disaster. Waves of destruction cause nerve and glial cells in the spinal cord to die. The body contains the damage. That, however, prevents recovery.

The spinal cord is 44 cm long and has a diameter of only 1 cm. It is no thicker than a pencil. If you’d touch it, it would feel like gelatin. And it is extremely fragile. Fortunately, it is well protected within a thick layer of bone, the cerebrospinal fluid and three meninges. If an injury is too severe, however, all the protection proves insufficient and the complex and delicate tissue is critically damaged. Nerve and glial cells die within minutes to hours after the injury. This initial damage is then followed by “secondary damage”. Blood vessels rupture, leading to swelling and oxygen deficiency in the tissue. Other nerve cells die and the damage spreads.

No spinal cord injury is like the other, so it's difficult to explain the complicated processes that happen hours to months later. Some events overlap in time and even influence each other. In any case, the spinal cord enters an emergency mode. It tries to repair or limit the damage. The same mechanism can be both healing and harmful at the same time. For the sake of clarity, we can simplify the events and subdivide them into four “waves”:

The first wave: Minutes to hours after
Shortly after an injury, highly toxic conditions prevail for the spinal cord. The cells lack oxygen and energy, which leads to their demise. They burst and release huge amounts of toxic substances that kill even more cells.

The second wave: Hours to days after
The spinal cord begins to heal itself. New blood vessels are formed to return oxygen and new energy to the damaged tissue. This attracts several immune cells that begin to eliminate cell debris. While these mechanisms purify the environment of toxic substances, they also generate reactive free radicals that cause further damage.
In addition, the injury also “stuns” the entire immune system. For the injured person, this often causes lung or bladder infections and hampers general recovery.

The third wave: Days to weeks have passed
The body now closes the wound. Connective tissue and immune cells form a first scar tissue. To prevent further damage, the body shields the intact spinal cord with a thick layer of glial cells. The resulting scar tissue solidifies and prevents regeneration. It basically creates a no-man's land in the spine where neurons cannot grow. Dead nerve cells are not replaced by new ones.

The fourth and final wave: Weeks to months after
During this last wave, the restoration of tissue structures and functions is limited. Nerve pathways that have remained intact change and take on lost functions such as movement and sensation. This phenomenon (plasticity) creates a bypass that extends around the aforementioned no-man's land.

These incredibly complex events partly explain why finding a cure is so difficult. The good news is that scientists have already discovered many pieces of the puzzle. Drugs that are designed to control the toxic conditions immediately after an injury are currently being studied in clinical trials. During the second wave, doctors and nurses are required to detect infections early and treat them immediately.Completely preventing scar formation during the third wave is not a viable solution, since the toxic substances formed in the first phase would spread. However, ongoing research shows that scar modification offers a good chance of recovery. Rehabilitation is often very successful during the fourth wave, although results vary from patient to patient. The key, it seems, is for researchers to promote positive events while reducing harmful side effects.

 

Glossary

Glia – also called glial cells, are supporting cells of the nervous system. The term derives from Greek γλία "glue". Glia cells take on several functions such as providing physical support to nerves and cells, as well as forming the myelin insulation of nervous pathways.  

Neurons
– The human brain and spinal cord both contain billions of neurons (nerve cells). In order for us to think, feel, and act, neurons need to be in constant communication with each other. Information is transmitted via electrical and chemical signals.