Traumatic Spinal Cord Injury's Secondary Injury Cascade

The secondary injury cascade is a series of changes that begin within just a few hours after the SCI and may continue months past the initial injury.

Written by Michael G. Fehlings, MD, PhD, FRCSC, FACS

If you’ve endured a traumatic spinal cord injury (SCI), the damage to your spine can continue and evolve long past the initial injury. This is because traumatic SCI produces 2 types of injuries: primary and secondary.

The primary injury is caused by the initial traumatic event, and the secondary injury is created by a series of biological and functional changes. Your doctor may refer to the later changes as the secondary injury cascade.
Traumatic Spinal Cord Injury: Primary and Secondary Injuries
The primary injury is the structural damage to your spine, such as dislocation or fracture of a vertebral body with subsequent spinal cord compression, caused by the initial traumatic event.

In addition to the primary structural injury(ies), nearby glial cells and nerve cells in your spinal cord become injured and prevent your spinal cord from getting the blood it needs. Glial cells provide nutrients and other support to the nerve cells in your central nervous system, which consists of your brain and spinal cord.

It’s this initial structural and cellular damage that triggers the secondary injury cascade. As the name suggests, the secondary injury cascade is a series of changes—often developing one after the other—that begin within just a few hours after the SCI and may continue more than 6 months past the initial injury.

The primary and secondary damage caused by traumatic SCI occurs in the following phases:

Acute Injury Phase
During the acute injury phase, injured glial and nerve cells in your spinal cord begin to die. Blood vessels in your spinal cord affected by the injury may lose function, which may reduce blood supply to your spinal cord—inadequate blood supply is called ischemia.

Blood vessel injury may cause hemorrhaging, which can expose your spinal cord to inflammatory cells that can stay in your spinal cord for weeks after your injury. These inflammatory cells can cause your spinal cord to swell, causing further spinal cord compression and worsening your initial injury.

Subacute Injury Phase
The nerve cell dysfunction and blood supply problems that began in the acute phase may spiral further in the subacute injury phase. During this phase, interrupted blood supply may lead to an imbalance of cell homeostasis, cell death, and inflammatory cellular responses that can cause additional damage to your spinal cord.

As glial and nerve cells within your spinal cord die, they release substances that activate other cells that bolster the invading inflammatory cells. When this occurs, the cells cause more inflammation at the damage site and promote further glial and nerve cell death.

As cells die, blood supply decreases and inflammation increases—your spinal cord’s ability to protect itself is threatened. And it’s these ensuing secondary injuries that can be more serious than the original primary injury.

Intermediate-Chronic Injury Phase
Once the damage caused by the acute and subacute phases slows, your spinal cord attempts to repair itself in the intermediate and chronic injury phases.

The formation of cystic cavities and glial scars are 2 ways your spinal cord tries to protect itself at the site of the damage.

Another line of defense for your spinal cord is known as remyelination. Remyelination occurs when surviving nerve cells create new myelin sheaths (the protective covering of nerve cells) for damaged nerve cells.

Your spinal cord can also internally repair some of the damage from the secondary injury cascade. Nerve cells within your spinal cord can adapt and change to promote sustained recovery (this is known as plasticity), and other precursor glial cells can create new glial and nerve cells to support the regenerative process for years after the initial injury.

Current Research Supports the Spine’s Ability to Self-Heal
Finding ways that therapeutically support the spinal cord’s internal repair processes are a focus of current spinal cord injury research. You can learn more about the latest in protective and regenerative therapies in Spinal Cord Injury Clinical Trials and Innovative Therapies.

Suggested Additional Reading
A special issue of the Global Spine Journal set forth guidelines for the Management of Degenerative Myelopathy and Acute Spinal Cord Injury, which is summarized on SpineUniverse in Summary of the Clinical Practice Guidelines for the Management of Degenerative Cervical Myelopathy and Traumatic Spinal Cord Injury.

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