By operating on the nerves of a patient’s upper arm, rather than his injured spine, surgeons at the Washington University School of Medicine in St. Louis restored some hand function to a quadriplegic. First performed about two years ago, the case study was recently announced in the Journal of Neurosurgery. The surgery, according to the study authors, was the first reported case of using nerve transfer to restore the ability to flex the thumb and index finger after a spinal cord injury.
Dr. Ida Fox, an assistant professor of plastic and reconstructive surgery who treats patients at Barnes-Jewish Hospital, performed the second surgery of this kind. Below are excerpts from our recent interview.
Only quadriplegics with a specific type of injury are eligible for this procedure. Why are they ideal candidates?
We’re trying to get the tip of the thumb and the tip of the index finger to bend, so they can pick up small objects. We have to rob Peter to pay Paul. We need something close by we can switch over to get that function. The patients who qualify for this transfer are patients who are C6 or C7 motor level injury quadriplegic patients. Their spinal cord has an injury. All the nerves below the level [of injury] are working. Those are the nerves that go to the hand, but they’re not connected to the brain. We need to reestablish that connection to the brain by stealing the nerve above the level of spinal cord injury, which is connected to the brain, and rewiring it to the nerves below that level. With the spinal cord injury at a specific site, we’re able to restore that function.
What’s the ultimate goal of the surgery?
These patients have figured out ways to use their arms even though not all the muscles are working. They’re able to move their fingers by moving their wrist back and forth. They’re able to hold things. But if they inadvertently straighten their wrist, their hand will open and they’ll drop the object. We wanted to add the ability to lift things without depending on the wrist to manipulate the fingers and provide more independent finger motion. It makes things faster for them. It lets them use utensils or a writing instrument without an assistive device. It makes us human to have that ability to hold things precisely between the thumb and index finger.
Instead of operating on the spine, you target the nerves of the upper arms. Why?
We don’t have the ability to make the central nervous system, which includes the spinal cord, regenerate. There’s been a lot of work trying to bring peripheral nerve tissue into the central nervous system to make it regenerate. But we still have not broken the code on how to make the spinal cord recover after injury.
The peripheral nervous system does have the ability to regenerate. If it’s a nerve that’s cut, we can put it back together and the nerve will grow back to the muscle and skin to restore motor function and sensation. We capitalize on that physiology in this case. We have to treat the central nervous system like a black box. We bypass the spinal cord injury we don’t know how to fix. When we do the nerve transfer, we create a peripheral nerve injury. We want to create that injury as close to the muscle as possible. We’re slicing over into a new nerve. When we cut the nerve that’s connected to the brain and slice it into the nerve that’s not connected to the brain because of the spinal cord injury, the nerve dies back to where we cut it. It has to grow back down the nerve tube to get back to the muscle. That growth occurs at an inch a month. If that nerve shoot doesn’t get back to the nerve within a year, the muscle will be unresponsive. The closer we are to the muscle, the faster the recovery.
What’s innovative about this technique?
Nerve transfer is not a new concept. It’s been popularized in the last 10 years for patients with peripheral nerve injuries. We started doing nerve transfers toward the fingertips and stealing extra nerves to restore function more quickly. In the last 10 years, that’s become much more popular. Applying that concept to patients with spinal cord injuries is a new part.
These are well-established procedures that haven’t been used in this patient population. Patients with spinal cord injury have a blockage between the brain and those nerves. The muscle and the nerve are alive below the level of spinal cord injury. The cell of the nerve is sitting in the spinal cord. That long shoot is the peripheral nerve. It goes out to the muscle. That connection is intact in patients with spinal cord injury. That’s unlike peripheral nerve injury where the nerve fiber itself is cut. That’s the different physiology of these two patient populations that we exploit.
How did you figure out this technique would work for these patients?
It’s a bit of luck and happenstance. My partner Susan Mackinnon, who did the first procedure, shared the story of what brought her to this point. The patient had been a practicing trauma surgeon. On his way to a surgery, he was in a motor vehicle crash and became quadriplegic. His friend, a plastic surgeon, [suggested he meet Dr. Mackinnon, a peripheral nerve expert]. They went to see if she could help him. [Dr. Mackinnon] walked into one of our patient rooms and, knowing everything she does about peripheral nerves, it just came to her. She thought she’d harness this technique.
This is a gentleman who is a surgeon, so he understands the risks of surgery. It took out all the things we worry about when we’re doing something outside the expected. She did [the surgery] and sat on it. We’d only done it in the one patient to make sure it worked. At about six months, he began getting a twitch of function. At 12 months, he was able to feed himself independently. That instigated the publishing of the case report. We have a clear clinical result that shows this does work.
Describe the process of the surgery.
We make an incision on the inner aspect of the arm above the elbow. We go through a layer of fatty tissue. The nerves are there. The median nerve is the nerve we’re transferring into. It goes to the muscle that controls the bend of the thumb and index finger. Near the biceps muscle, which bends the elbow, we peel the muscle up. Underneath it is a nerve that bends the elbow. We’re going to sacrifice the nerve to that muscle. We use a handheld nerve stimulator to give a little electric current. We can see the fingers moving as we tap on the nerve. We figure out which piece of the nerve we want. We use microscopic instruments to tease out the bit that’s going to the thumb and index finger. We make sure it’s going to the muscle we want. We cut it. We go over the other nerve and cut it. We flip-flop the two nerves over each other and use a tiny suture to stitch the two pieces together again.
What happens after the surgery? What were the results of the patient in your case study?
The nerve has to grow back to the muscle. It will take several months. Once it gets to the muscle, the patient has to do intensive physical therapy. The patient has to re-learn that the nerve that used to give the signal to bend the elbow now gives the signal to bend the thumb and the tip of the index finger. It’s a bit of a mind game. Eventually their brain re-learns and they don’t have to think about it. It takes time to adapt. It will also take time to strengthen the muscle that hasn’t been used since the spinal cord injury.
What’s next for this work?
We’re continuing to move forward and offering it to additional patients. A single case study, while helpful and important, needs to be taken a little bit critically. We need to make sure we can get similar results in a larger patient population.
The important thing about the surgery is we’re careful not to burn any bridges. We’re taking a muscle that cannot be used for more traditional surgeries, such as tendon transfers, because of its location and anatomy. We’re preserving all the traditional options in this patient population. That’s critical to think about. While we’re extremely excited, we need to be cautious and meticulous.
Watch a video on the second year results of the initial patient.
Photo: Dr. Ida Fox / Courtesy of Washington University
Image: 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). / Eric Young