New hope for paraplegics

Three further patients with chronic paraparesis regain their ability to walk by electrical stimulation of the spinal cord via a wireless implant.

Targeted neurotechnology promising for patients with severe spinal cord injury

Three further patients with chronic paraparesis regain their ability to walk by electrical stimulation of the spinal cord via a wireless implant.

Three patients who had suffered cervical cross section injuries more than four years ago and had remained completely paretic despite some remaining nerve connections at the injury site and extensive rehabilitation can now walk again on crutches or a walker. This is due to a new rehabilitation protocol that combines precise electrical stimulation of the lumbar spinal cord with weight-assisted therapy.

After a few months, patients were able to control their previously paralyzed limb muscles again arbitrarily, even in the absence of electrical stimulation, as Swiss researchers reported in Nature on 31 October (Sources 1-3).

Never-before-seen level of precision in spinal cord stimulation

Years of research on animal models have contributed to a detailed understanding of the underlying mechanisms. "This enables us to imitate in real time how the brain normally activates the spinal cord," says neuroscientist Grégoire Courtine. "Precise timing and localization of electrical stimulation are critical to the patient's ability to perform a planned movement. It is also this spatial-temporal simultaneity that triggers the growth of new nerve connections."

Selected configurations of the implanted pulse generator and the arrangement of the electrodes allow the targeted activation of specific regions of the spinal cord so that individual muscles in the legs can be controlled.

First Steps

The patients did not need much time to learn the coordination between the intention to walk and the targeted electrical stimulation. All three were able to walk again after one week of calibration with weight support and the arbitrary muscle control improved considerably over the following five months of training.

The new approach allows active running training over the floor instead of treadmill training or passive exercises such as exoskeleton-assisted steps. In the rehabilitation sessions, participants were able to walk one-kilometer hands-free using an intelligent weight support system. 

Unlike other studies, the regained neurological function was maintained beyond training - even when the stimulation was switched off. In addition, there was no fatigue of the leg muscles. Thus, high-intensity training units are possible which seem to be essential for triggering activity-dependent plasticity. This refers to the ability of the nervous system to reorganize nerve fibers. This leads to an improvement of the motor function even when the stimulation is switched off.

Previous work with more empirical approaches, such as continuous electrical stimulation protocols, enabled only a few selected patients to walk with walking aids - even over short distances and when the stimulation was switched on. When the stimulation was stopped, the affected persons were immediately plegic again and could no longer activate any limb movements. Continuous stimulation can also interfere with the perception of the spatial position of the extremities.

Aiming for the development of a widely available therapy

The new approach will also be tested early post-traumatically if the rehabilitation potential is high and the neuromuscular system has not yet undergone atrophy resulting from chronic paralysis.

The "MIT Technology Review" selected the research work of Prof. Grégoire Courtine as the breakthrough of 2017. Further detailed information and animations for doctors and patients are available on the website of the specially founded startup GTX medical.

Sources:
1. Hamers, L. Stimulating the spinal cord helps 3 more paralyzed people walk. Science News (2018). Available at: https://www.sciencenews.org/article/stimulating-spinal-cord-helps-more-paralyzed-people-walk. (Accessed: 9th November 2018)
2. Wagner, F. B. et al. Targeted neurotechnology restores walking in humans with spinal cord injury. Nature 563, 65 (2018).
3. Breakthrough in treating paralysis: Targeted neurotechnology restores walking in humans with spinal cord injury. ScienceDaily Available 
at: https://www.sciencedaily.com/releases/2018/10/181031141523.htm. (Accessed: 9th November 2018)

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