Monkeys with spinal injuries that have left them paralysed are able to walk again through wireless implants in their brains and spines that bypass the damaged tissue.

Scientists developed a brain-spinal interface to transmit neural signals from the brain to a site in the spinal cord downstream of the injury. The device acts to form a wireless bridge to overcome the broken nerve tissue. The research is published in the journal Nature.

First steps

The device was fitted into two rhesus monkeys in a 10-hour operation. An implant in the monkey's motor cortex – the outer layer of the brain – detects the monkey's intended movements. This device then wirelessly sends signals to a computer, which interprets the signals using a mathematical algorithm.

macaque monkey
A macaque monkey Newcastle University

The computer then transmits the signals to a receiver implanted in the spine beyond the site of injury. This transmits the intended electrical signals to the spinal cord.

Within a week one monkey was able to walk. The second monkey was able to walk within two weeks.

Study author Grégoire Courtine of the Swiss Federal Institute of Technology in Switzerland Courtine and his colleagues fitted the device to monkeys were entirely unable to use one of their legs. The monkeys had been temporarily paralysed so that the leg was not receiving any information from the brain, Courtine told IBTimes UK.

This state lasts for a few weeks before nerves regrow and the monkey regains control of the leg, he says. "We don't do bilateral paralysis in the monkeys because it would be ethically indefensible, and would have too much impact on the wellbeing and health of the animal," he says.

Courtine says that study is the critical step between previous research using such devices in rodents and a viable clinical trial in humans.

Brain implant
Grégoire Courtine holds a silicon model of a primate’s brain and a brain implant. The brain-spine interface uses a microelectrode array like this one to detect spiking activity of the brain’s motor cortex Alain Herzog / EPFL

Hope for paralysis patients

"We are now able to start the first clinical study of people with spinal cord injury," he says. "We have received permission to implant this technology in eight people with spinal cord injuries. Indeed, we have already started this clinical study. So two participants are now starting this clinical trial."

Courtine predicts that the research will be a viable option for paralysis patients within 10 years.

At the moment the monkey had to stay close to the computer running the algorithm that was transmitting information to and from the wireless devices. However, Courtine says that it does not take a very powerful computer to run the algorithm necessary for the devices. "When you have developed the mathematical algorithm then it can operate fairly easily on ordinary electronics," Courtine says. "The mathematical models will fit on a USB key."

Neurosurgeon Jocelyne Bloch of the Lausanne University Hospital, who surgically implanted the brain and spinal cord implants, says: "The link between the decoding of the brain and the stimulation of the spinal cord – to make this communication exist – is completely new.

"For the first time, I can imagine a completely paralysed patient able to move their legs through this brain-spine interface."

Brain implant
The brain-spine interface uses a brain implant like this one to detect spiking activity of the brain’s motor cortex. Seen here, a microelectrode array and a silicon model of a primate’s brain Alain Herzog / EPFL