A 71-year-old quadriplegic man can move his fingers after surgeons "stole" healthy nerves from his arm and rerouted them to his hand, according to a new case study.
The man, whose name has not been released, crushed his spinal cord at the C7 vertebrae in the base of his neck in a 2008 motor vehicle accident. The injury severed the nerve circuits that would send signals from his brain to the muscles in his hands, but it spared nearby nerves that could be coaxed into taking over.
"It's called nerve transfer surgery," said Dr. Ida Fox, assistant professor of plastic and reconstructive surgery at Washington University in St. Louis. "It's borrowing a nerve that's still working and displacing it into a nerve that isn't working."
People with C7 spinal cord injuries can't move their hands, but they can move their shoulders, elbows and wrists, thanks to nerves that originate above the injury. To tap into those healthy circuits, Fox and colleagues cut the nerve that controlled the man's brachialis, an arm muscle that helps bend the elbow. They then attached it to the non-working nerve projecting out to his hand with a tiny stitch the size of a hair.
"We had to sacrifice something that's 'sacrificable,'" said Fox, describing how the biceps and other elbow-bending muscles would pick up the brachialis' slack.
Over six months, the nerve, which is no thicker than a strand of angel hair pasta, grew six inches along the old non-working nerve, reaching the hand muscles at the end. And with intense physical therapy, the man learned to move his fingers with the nerve that once bent his arm.
"The brain has to be trained to think, "OK, I used to bend my elbow with this nerve, and now I use it to pinch,'" said Fox. "We're not changing any of the biomechanics; we're just changing the wiring. So it's more of a mental game that patients have to play with themselves."
The case study, published today in the Journal of Neurosurgery, could give surgeons a tricky tool to help spinal cord injury patients hold onto some independence, Fox said.
"These patients have figured out very clever adaptive strategies to get around the fact that their hands don't do what they want them to do. But they want to be able to do things more quickly without help," said Fox, adding that patients frequently say they wish they could eat without assistive devices. "This makes stealing that brachialis muscle worth it."
One year after the procedure, the man is able to feed himself bite-size pieces of food.
But Fox cautioned that the technique isn't for everyone. Had the man's injury been further down in his spinal cord, he would have maintained control over his hands. And had it been higher up, the nerve to his brachialis would not have worked either, according to Fox.
"In patients with injuries that are higher up, we don't have the extra muscles to steal nerves from because so many aren't working," she said.
The technique exploits the ability of peripheral nerves, those that send signals between the spinal cord and the muscles, to regenerate -- a trait that sets them apart from nerves inside the spinal cord.
"Despite years of research, we haven't figured out how to make the spinal cord work again," said Fox. "But we know nerves in the peripheral nervous system can regenerate, and that's what we're trying to exploit here."