What happens after a spinal cord injury?

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After a spinal cord injury, numerous reactions are triggered in the body. The biologist Vieri Failli gives us an insight of how one leads to the other.

Let's start with the facts: The spinal cord is on average about 40 to 50cm long. At it's thickest point, it is not much thicker than a pencil. If you touch it, it would feel like gelatin. And it is extremely fragile. Fortunately, it is well protected within the cerebrospinal fluid, three different layers of connective tissue (meninges) and a thick layer of bone. If an injury is too strong, all that protection is insufficient and the complex and delicate tissue is severely damaged.

The devastating spinal cord injury
If the spine is injured and sensitive tissue is destroyed, nerve and glial cells die within minutes to hours. This first damage is then followed by a “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 “waves”.

The first wave: Only a few hours
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 a few days afterwards
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 worse general recovery.

The third wave: Days to weeks pass
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 (figure 6). The resulting scar tissue freezes 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: After weeks to months.
During this last wave, there is limited restoration of tissue structures and functions. 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 no-man's land.

Although I've simplified the whole picture, the main message is pretty clear: Any spinal cord injury is incredibly complex. This partly explains why finding a cure is so difficult. Scientists have now discovered many pieces of the puzzle. In clinical studies, drugs are being studied that are designed to control the toxic conditions immediately after an injury (Riluzole). Doctors and nurses are required in the care of patients to detect infections early and treat them immediately. Completely preventing the scar formation would not be a solution since the toxic substances formed in the first phase would otherwise spread. However, ongoing research shows that scar modification offers a good chance of recovery. Rehabilitation is often very successful here, although it varies from patient to patient.
The key, it seems to me, is for researchers to promote positive events while reducing harmful side effects.

Yours Vieri Failli