Spinal Cord Injury | What happens in the spinal cord after injury?

What Happens to the Spinal Cord After Injury?

Spinal cord injury has two phases: primary injury, the immediate mechanical damage, and secondary injury, a chain of biological events that can continue from minutes after the injury through months or even years.

1. Primary Injury: Immediate Mechanical Damage

• A fracture or break in the vertebrae can cause bone fragments to strike or compress the spinal cord.
• This can damage axons, interrupting the signals they carry, and rupture cell membranes, allowing cell contents to leak out.
• Small blood vessels within the spinal cord may also be damaged, even when the major spinal arteries are unaffected.

2. Secondary Injury: Cascading Damage

Damage to blood vessels and spinal cord tissue can set off processes that worsen the initial injury:

• Reduced blood flow and oxygen: Leaking blood can increase pressure within the spinal cord and reduce the oxygen and nutrients reaching its cells. Blood loss can also lower overall blood pressure.
• Shock and vessel constriction: The body may activate the sympathetic “fight-or-flight” response to raise blood pressure by constricting intact blood vessels. This can further reduce blood flow to the spinal cord.
• Energy failure and cell death: Without enough oxygen and nutrients, cells cannot make sufficient energy, and important cellular processes stop working.
• Ion imbalance: Neurons normally use energy-dependent pumps to move sodium out of cells and potassium in. When energy is lacking, sodium can build up inside neurons. A compensating exchange can bring calcium into the cells, and excessive calcium can trigger cell death.
• Excitotoxicity: Dying neurons can release glutamate. Excessive glutamate can overstimulate neighboring neurons, allowing more sodium and calcium to enter and causing further cell damage. This creates a cascading cycle of cell death.
• Inflammation and scar formation: Inflammation helps clean up damage and repair tissue, but it is not specific to spinal cord neurons. The response can also contribute to cell loss and formation of a glial scar, involving cells such as astrocytes and microglia. The scar may obstruct pathways needed for signals to travel through the spinal cord.

3. Research Approaches Discussed

The video describes possible strategies being investigated, including in animal models:

• Boost autophagy: Autophagy removes and recycles damaged cellular material, potentially limiting harmful leakage from injured cells.
• Block sodium–calcium exchange or related channels: The aim is to reduce harmful ion imbalances, especially excess calcium entering cells.
• Reduce glutamate excitotoxicity: Blocking glutamate receptors may help prevent overstimulation and further neuronal damage.
• Limit harmful scarring while preserving repair: Researchers are looking for ways to retain inflammation’s useful cleanup and repair functions while reducing the formation of a scar that blocks spinal cord pathways.

These approaches are research findings, not established treatments for people with spinal cord injuries.

Speaker

• Dr Mike — the video’s presenter and sole speaker identified in the subtitles.