Think of the spinal cord as a busy motorway, and cars as the electrical signals travelling from distant sites to the busy terminus that is the brain. When a spinal cord injury occurs, the cars are stopped in their tracks at the site of the injury. No more cars reach the brain from anywhere after the injury site. No matter how many more cars it sends out, none reach their destination if it is further away than the injury.
This is a simplification of course; some injuries don’t damage all the way through the spinal cord, only affecting one lane of the motorway in one direction. Sometimes there are alternative routes so even though the motorway itself is damaged, a side road can still reach the destination.
Some spinal cord injuries are instant. Like a sinkhole opening up and enveloping the entire motorway. These are traumatic spinal cord injuries, and are the most researched due to their devastating nature. In real terms, these occur during falls, and vehicle accidents. Other, non-traumatic injuries take longer to occur. Think of these as roadworks which don’t ever get finished, instead incorporating more lanes. Caused by tumours, infections, or degeneration of the spine, these non-traumatic injuries are considerably less well researched, and are the subject of my own PhD.
Non-traumatic spinal cord injuries in themselves are interesting. As the first lanes get closed on the motorway, traffic can still reach its destination using the available lanes or even side roads. In the spinal cord, making more connections is termed plasticity. In the early stages of non-traumatic injury, no symptoms occur. As more lanes get closed, there isn’t even enough space on these side roads, and fewer cars arrive at the terminus. In patients, this corresponds to the onset of symptoms. Gradually, these deteriorate as the spinal cord becomes more and more compressed and ultimately paralysis can result.
The number of people suffering non-traumatic injuries is hard to determine; some estimates suggest over twice as many people are inflicted by such injuries compared to traumatic spinal cord injuries. However, only a handful of countries have national databases. Nevertheless, since these injuries are caused by disease such as cancer and degeneration; both age-related conditions; the rate of this injury is likely to increase.
There are many unanswered questions in non-traumatic spinal cord injury research: what actually happens in the spinal cord itself – how do the nerve cells respond? How do they use and accentuate plasticity within the spinal cord? Can interventions (drugs or surgical procedures) improve the outcomes for patients? Researchers, including myself, are using experimental models to try and better understand the processes involved in non-traumatic spinal cord injury. A deeper understanding of the disease process is key to future development of treatments.