Two men who were paralysed in separate accidents more than six years ago can stand and walk short distances on crutches after their spinal cords were treated with electrical stimulation.

David Mzee, 28, and Gert-Jan Oskam, 35, had electrical pulses beamed into their spines to stimulate their leg muscles as they practised walking in a supportive harness on a treadmill.

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Doctors believe the timing of the pulses – to coincide with natural movement signals that were still being sent from the patients’ brains – was crucial. It appeared to encourage nerves that bypassed the injuries to form new connections and improve the men’s muscle control.

In many spinal cord injuries a small portion of nerves remain intact but the signals they carry are too feeble to move limbs or support a person’s body weight.

“They have both recovered control of their paralysed muscles and I don’t think anyone with a chronic injury, one they’ve had for six or seven years, has been able to do that before,” said Grégoire Courtine, a neuroscientist at the Swiss Federal Institute of Technology in Lausanne.

“When you stimulate the nerves like this it triggers plasticity in the cells. The brain is trying to stimulate, and we stimulate at same time, and we think that triggers the growth of new nerve connections.”

Mzee was paralysed in a gymnastics accident in 2010. He recovered the use of his upper body and some control of his right leg after intensive rehabilitation at a paraplegic centre in Zurich. Doctors there told him further improvement was unlikely, but after five months of training with electrical stimulation, he regained control of the muscles in his right leg and can now take a few steps without assistance.

Oskam was paralysed in a traffic accident while cycling home from work in 2011. He could not walk before the study but can now take a few steps outside with crutches and believes he will soon go one better. “I should be able to have a BBQ standing on my own in the near future,” he said.

The treatment is far from a cure for paralysis: while both patients continue to improve, they still use wheelchairs in their daily lives. But doctors believe the work is an important proof of principle. It shows that precisely timed electrical stimulation can help recover some of the movement patients lose when they suffer such devastating injuries.

“The big challenge is whether it can really change their life,” said Courtine. “This is an important first step, but the key now is to apply this very early after an injury when the potential for recovery is much larger.” His next trial will include patients whose injuries are no more than a month old.

The scientists developed the electrical stimulation procedure to help paraplegics walk by activating the necessary leg muscles in precisely the right order. The pulses were delivered to the relevant nerves by wireless electrodes implanted in the lower back. Details of the work are reported in Nature and Nature Neuroscience.

Scientists found that after a week of training, Mzee, Oksam and a third man, Sebastian Tobler, who had a more severe spinal injury, could all walk with electrical stimulation, provided they were supported by a harness. While Tobler cannot walk without stimulation, he uses the system to train on the treadmill, and has an adapted version for a specially adapted trike that he uses for off-road biking.

Facebook Twitter Pinterest Composite of David Mzee standing and walking. Photograph: Hillary Sanctuary/EPFL/Handout

Last month two separate teams announced that a number of other patients had managed a handful of steps with implants that delivered continuous electrical stimulation to their spinal cords. None of the patients were able to walk when the electrical pulses were turned off, however, perhaps because continuous stimulation is less effective at encouraging the growth of new nerve connections.

In an accompanying article in Nature Neuroscience, Chet Moritz at the University of Washington in Seattle said “it now appears that many people can regain the ability to control their paralysed limbs and even walk again through the innovative combination of spinal stimulation and rehabilitation ... This stimulation combined with rehabilitation is actually helping to direct plasticity and healing of the nervous system around the injury.”

Taking all of the recent studies together, he said, “we should consider these results across three independent research groups as a breakthrough in the treatment of paralysis,. The field of spinal cord injury is poised to take a giant leap forward in the treatment of what was until very recently considered incurable: paralysis.”

