Three people who were completely paralysed from the waist down due to spinal cord injuries can now walk while using wheeled walking frames or crutches for support, thanks to implants that electrically stimulate nerves in their back and legs.
“All three patients immediately after the surgery were able to stand up and to step [with support],” says Jocelyne Bloch at Lausanne University Hospital in Switzerland, who carried out the surgery.
“On the first day, I was able to see my legs moving and it was very, very emotional,” says one of the recipients, an Italian man called Michel Roccati. After three to four months of training, he could walk outside using a walker.
Several groups have been investigating using implants to stimulate nerves of the spinal cord in people who have injured them, but most have focused on people with lesser injuries and more intact nerves. The idea is that the stimulation makes the remaining nerves more excitable and so amplifies the weak signals from the brain to the legs, although it takes months of training.
In the new study, the three men, who had all been injured for more than a year, had complete paralysis from the waist down. The instant results hinge on using purpose-built electrodes.
“This is a monumentally huge step forward,” says Ronaldo Ichiyama at the University of Leeds, UK. “However, we need to see this reported in more people before we get too excited.”
Roccati, who was paralysed in a motorbike crash in 2017, now uses the implanted device for 1 to 2 hours a day, including for going for walks on his own. He can also stand up for 2 hours, cycle and even swim, by choosing different stimulation programs. He finds walking or standing helps relieve pain caused by sitting in a wheelchair all day.
Users choose what kind of patterns of movement they need through a tablet computer. This links wirelessly to a device called a neurostimulator put into their abdomen, which connects to electrodes on their spine. The neurostimulator will have to be replaced after about nine years, although the electrodes should last the lifetime of the recipient.
Roccati feels some sensations when the implant starts working, as does another user, but the third person in this study, who had the most severe spinal cord injury, feels no sensations, says Grégoire Courtine at the Swiss Federal Institute of Technology in Lausanne (EPFL), who co-led the research with Bloch.
Roccati is also seeing small improvements in function even when the stimulation is turned off. This shows his spinal nerves weren’t completely severed, although he was classed as having complete paralysis of the legs. “He can induce movements, but not really move his leg voluntarily. It’s really dependent upon the stimulation turned on to have this recovery,” says Courtine.
Other previous work had used spinal implants designed for people who need relief from severe pain caused by spinal injury. But these implants aren’t powerful enough to reach all the different nerves needed for triggering the complex movement patterns required for stepping motions.
In the new approach, Courtine and his team worked with their technology spin-off company, Onward Medical, to develop larger electrodes that could target all the nerves needed. Each person has 16 electrodes implanted, although the team wants to put 32 into future recipients.
The computer software that controls the electrodes to achieve different patterns of movement is also an advance. The electrodes are tested during the surgery. “Sometimes you have an electrode not exactly at the perfect location, a patient will have the [nerves] a little bit distributed differently. So we have to tune the electrode and tune the timing,” says Bloch.
The group believes its approach could in theory help other paralysed people who have at least 6 centimetres of healthy spinal cord beneath the injury so there is room to implant all the electrodes. Onward Medical is planning a larger trial of the implants this year to test their effect on blood pressure, as spinal cord injuries can disrupt its regulation. They won’t be available outside trials for several years, says Bloch.
Journal reference: Nature Medicine, DOI: 10.1038/s41591-021-01663-5
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