People with complete paralysis walk again after nerve stimulation breakthrough: ScienceAlert

Using a mix of electrical stimulation and intense physical therapy, nIn people with chronic spinal injuries, the ability to walk is restored.

All suffered severe or complete paralysis due to spinal cord damage. Incredibly, the volunteers all saw immediate improvements and continued to show improvements five months later.

A recent study by researchers at the Swiss research group NeuroRestore has identified the exact nerve groups stimulated by the therapy, using mice as the starting point.

The nerve cells that orchestrate walking are located in the part of the spinal cord that runs through our lower back. Injuries to our spinal cord can interrupt the brain’s chain of signals, preventing us from walking even if these specific lumbar neurons are still intact.

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In fact, because they cannot receive commands, these ‘walking’ neurons become inoperative, potentially leading to permanent paralysis of the legs.

Previous research has shown: electrical stimulation of the spinal cord can reverse such paralysis, but how this happened was not clear. So neuroscientist Claudia Kathe of the Swiss Federal Institute of Technology Lausanne (EPFL) and colleagues tested a technology called epidural electrical stimulation in nine individuals, as well as in an animal model.

The spinal cord was stimulated by a surgically implanted neurotransmitter. Meanwhile, patients also underwent a process of intensive neurorehabilitation in which a robotic support system assisted them as they moved in multiple directions.

The patients underwent five months of stimulation and rehabilitation, four to five times a week. Amazingly, all volunteers were then able to take steps using a walker.

To the researchers’ surprise, the recovered patients even showed a reduction in neural activity in the lumbar spinal cord while walking. The team thinks this is because the activity is refined to a specific subset of neurons that are essential for walking.

“If you think about it, it shouldn’t come as a surprise,” Courtine told Dyani Lewis at Nature“because in the brain, when you learn a task, that’s exactly what you see – fewer and fewer neurons are activated” as you get better at it.

So Kathe and team modeled the process in mice and used a combination of RNA sequencing and spatial transcriptomics – a technique that allows scientists to measure and map gene activity in specific tissues – to understand which cells did what.

They identified a single population of previously unknown neurons that can ramp up to take over after injury, found in the intermediate laminae of the lumbar spinal cord.

This tissue, made up of cells called SC^Vsx2::Hoxa10 neurons do not appear to be necessary for walking in healthy animals, but they appear to be essential for recovery from spinal cord injury, as destroying them prevented mice from recovering. However, their recruitment is activity dependent.

SC^Vsx2::Hoxa10 neurons are “uniquely positioned” to convert information from the brainstem into executive commands. These are then broadcast to the neurons responsible for the production of walking, Kathe and colleagues explain in their paper.

This is just one part of a very complicated chain of message and receive cells, so much remains to be explored.

But “these experiments confirmed that the participation of SC^Vsx2::Hoxa10 neurons is a fundamental requirement for the recovery of walking after paralysis,” the researchers said concluded.

This new understanding may eventually lead to more treatment options and may also improve quality of life for people with a variety of other spinal cord injuries.

Their research has been published in Nature.