Spinal Nerve Loss May Not Contribute to Multiple Sclerosis Disability

Synaptic loss in the spinal cord could lead to disability in patients with multiple sclerosis.

It has been thought that the loss of spinal nerve fibers is a major factor associated with disability in patients with multiple sclerosis (MS). This has led to the use of MRI to measure an area of the spinal cord in order to determine disability.

However, a new study published by Brain Pathology challenges the notion that spinal nerves lead to disability.

In the study, the authors sampled spinal cords of 13 patients with MS and 5 healthy patients. They discovered that the spinal cord cross sectional area may not be a good predictor of axonal death.

“The lack of association between axonal loss and spinal cord cross sectional area significantly changes our understanding of chronic disability in MS,” said lead researcher Klaus Schmierer, PhD.

The spinal cord is a bundle of nerves that spans from the base of the brain to the lower back. It relays messages between the brain and the nerves throughout the body. In MS, the immune system attacks the myelin, which protects the nerves from stimuli. Without the myelin, nerves can become damaged.

"In spinal cord trauma, people with less than 10% of their spinal cord axons may still be able to have useful lower limb movement, but in MS, patients with as much as 40% of their axons retained, as shown in our study, are almost invariably wheelchair bound,” Dr Schmierer said. “So, there is clearly something happening here which we've yet to understand."

The investigators revealed that the loss of synaptic connections in the spinal cord of patients with MS is significant. They speculate that this may be a main driver of disability.

The authors highlighted the need for additional studies to determine the driving factors behind MS-related disability. Currently, treatments for MS control symptoms and disease progression. If the underlying mechanisms of disability are discovered, it could identify potential new treatment options, according to the study.

“We need to identify other factors which -- over and above axonal loss -- determine the collapse of the spinal cord network and lead to the functional deficits seen in MS,” Dr Schmierer concluded.