You may have heard about connecting brains directly to robotic arms. However, that’s not the only way to allow a paralyzed person to pick up a soda. Susan Mackinnon, Andrew Yee and Wilson Ray from the Washington School of Medicine, St. Louis and their colleagues chose a different tactic to give a paralyzed man back the use of his hands.
The man had not been able to move his fingers since a car accident injured his spinal cord two years ago. This was because the nerve that normally activates hand muscles (shown in red below) originates below the injury site at the C7 vertebrate. Doctors determined that one of the nerves responsible for elbow function (green) originated above the injury and was still functional. The surgeons therefore attached the upper arm nerve to the hand nerve. Once this was done (in two separate surgeries, one for each hand), signals from the man’s brain that previously would have only affected his upper arms were now able to travel all the way to his hands.
To detour around the block in this patient's C7 spinal cord injury and return hand function, Mackinnon operated in the upper arms. There, the working nerves that connect above the injury (green) and the non-working nerves that connect below the injury (red) run parallel to each other, making it possible to tap into a functional nerve and direct those signals to a non-functional neighbor (yellow arrow).
This is by no means a quick fix. It took the patient ten months just to be able to pinch his thumbs and index fingers together. Nevertheless, everyone involved in this case has every reason to be pleased with the outcome. As of this writing, the patient can feed himself and even do some writing. There’s every expectation that he will continue to improve.