Nine patients paralyzed by spinal cord injuries were able to partially walk, recovering some degree of motor function through a process of spinal cord stimulation. They were part of a clinical trial coordinated by the two directors of the research, innovation and treatment center NeuroRestore – Grégoire Courtine, professor of neuroscience at the Technical University of Switzerland (EPFL) and Jocelyne Bloch, neurosurgeon at the University Hospital of Lausanne.
In the new study, published in the journal Nature, not only was the effectiveness of this therapy demonstrated in nine patients, but the improvement in motor function was shown to last in patients even after the neurorehabilitation process was completed and when the electrical stimulation was stopped.
This suggested that the nerve fibers used for walking had reorganized. The researchers believe it was crucial to understand exactly how this neural reorganization occurs in order to develop more effective treatments and improve the lives of as many patients as possible, according to Medical Xpress.
An unexpected finding: brain activity decreased during walking
This discovery was the culmination of several stages of fundamental research. For the first time, scientists were able to visualize the activity of a patient’s spinal cord while he was walking. This led to an unexpected finding: During the spinal cord stimulation process, neural activity actually decreased during walking. The scientists hypothesized that this was because neural activity was selectively directed toward recovery of motor function.
To test their hypothesis, the research team developed an advanced molecular technology.
“We have established the first 3D molecular mapping of the spinal cord. Our model allowed us to observe the recovery process with increased granularity – at the level of the neuron,” says neuroscience professor Grégoire Courtine.
Thanks to their highly accurate model, the scientists discovered that spinal cord stimulation activates Vsx2 neurons and that these neurons become increasingly important as the reorganization process proceeds.
A versatile spinal implant for a cure for paralysis
EPFL colleague Stéphanie Lacour helped the research team validate their findings using epidural implants developed in her lab. Lacour adapted the implants by adding light-emitting diodes that allowed the system to not only stimulate the spinal cord, but also turn off the Vsx2 neurons themselves through a process.
When the system was used on mice with a spinal cord injury, they immediately stopped walking as a result of the disabled neurons – but there was no effect on healthy mice. This implies that Vsx2 neurons are both necessary and sufficient for spinal cord stimulation therapies to be effective and lead to neuronal reorganization.
“It is essential for neuroscientists to be able to understand the specific role that each neural subpopulation plays in a complex activity like walking. Our new study, in which nine patients in clinical trials were able to recover some degree of motor function thanks to our implants, gives us valuable information about the process of reorganization of neurons in the spinal cord,” says Bloch.