An international group of scientists have organised a large-scale study resulting in the development of a new effective way of electrical stimulation of the spinal cord with paralysis. After checking the validity of the method in rodents, the researchers came to the conclusion about its potential use in humans for the purpose of recovery of their sensorimotor functions. Professor Pavel Musienko, Doctor of Medicine, head of the Neuroprosthesis Laboratory of SPbU Institute of Translational Biomedicine, senior researcher at the Ivan Pavlov Institute of Physiology of the Russian Academy of Sciences, head of the Laboratory of Neurophysiology and Experimental Neurorehabilitation at the Research Institute of Phthisiopulmonology of the Ministry of Health of the Russian Federation, actively participated in the work of the research group.
Today, more than 2 million people in the world cannot move due to heavy spinal cord injuries. Each year the number of paralysed patients increases by about 50 thousand people. The fight against the disease and the treatment of spinal cord injuries represent a comprehensive medical and socio-economic challenge acknowledged by the experts as relevant.
Earlier on, the experiments on animals and clinical studies have shown that neuromodulation of lumbar segment networks via electrical stimulation improves motor control after a spinal cord injury. This method had two major limitations however. First, until now it has been possible to stimulate only particular parts of the spinal cord. Second, stimulation occurred continuously throughout the entire locomotor activity and was not linked to a specific moment of muscle activity.
"Today, we have learned to control the reduction of certain muscle groups involved in the process of movement, in real time," said Pavel Musienko. "Thanks to computer simulation opportunities, we were able to identify the points of the spinal cord, stimulation of which in the future will help to solve the problem of the recovery of motor function in people."
During the research, the scientists have developed new protocols of stimulation that reproduce the natural dynamics of involvement of motor neurons and reduction of muscles during movement. Using computer modelling, the scientists have found the optimal position of the electrodes in the spinal cord to arouse contractions of certain muscle groups. This model has become the foundation of the design of spinal electrode arrays and programmed control, which, in real time and with high accuracy, modulates the work of extensor and flexor muscles. The scientists have developed an algorithm of stimulating some segments of the spinal cord by altering the electrical stimulation depending on the current motor abilities and the task at hand. Stimulation of specific segments of the left and right half of the spinal cord in rodents has made it possible to control the activity of various limbs' muscles when moving. Such spatiotemporal neuromodulation effectively restored the quality of walking, ability to support body weight, endurance and movement coordination in rats with severe spinal cord injuries.
"During our research we have created new implantation technologies, matrices of electrodes and an algorithm of neural networks stimulation with fine tuning based on feedback from limb movements," Pavel Musienko told. "It has turned out that this approach called 'spatiotemporal neuromodulation' was much more efficient than those we have used before."
Special methods of surgery have been designed for this study, including vertebral orthosis used to secure safe fastening of the devices on the spine, long-term functionality and good biointegration of the implant in the tissue. The effectiveness of these methods has been confirmed during a six-week functional and morphological research.
The developed technology opens up new opportunities both for fundamental research of the central nervous system and for neural prosthetics for treatment of diseases and injuries. The scientists believe that this approach can be applied in the development of scientific methods of neuromodulation for the restoration of motor activity in humans.
"In collaboration with SPbU medical scientists and our colleagues from the Laboratory of Neurophysiology and Experimental Neurorehabilitation at the Research Institute of Phthisiopulmonology of the Ministry of Health of the Russian Federation, we do everything possible to accelerate the translation of the developed technologies into clinical practice," Professor Musienko noted. "To date, several application for neuroprosthesis-related integrated projects have already been submitted, in particular to the Russian Science Foundation, Russian Foundation for Basic Research and NeuroNet. How soon Russia will be able to implement the developed neurorehabilitation approaches into clinical practice will largely depend on the state support and private investors."
Read more about the results of this study in the article Spatiotemporal neuromodulation therapies engaging muscle synergies improve motor control after spinal cord injury, Nature Medicine, 18 January 2016.