Researchers in London announced a paralyzed man was able to walk again, with braces and assistance, after groundbreaking surgery that implanted cells from his nose into his spinal cord. Assistant Professor of Neuroscience Wolfgang Stein explains how the doctors made it work, and what questions now remain.

This case does not mean that you will start seeing paralyzed people rising up from their beds in the near future, but it is a good start.

When there is damage to the nervous system, the path neurons use to send messages is severed. In adults, neurons in the brain do not grow back – except for one area, and that is the olfactory system that controls our sense of smell. For some reason, the olfactory system is funny. They are the only neurons that continue to grow and be replaced in the adult nervous system.

Now in a typical spinal cord injury, we are talking about a centimeter gap that has been created. That is a vast distance for neurons to try and regrow. And into this gap come cells – called glial cells. They move in and build a scar. That scar is the problem. Those glial cells inhibit the growth of axons, which are the pathways neurons use to talk with one another.

So the doctors decided to build a bridge over the gap, stimulate axon growth and try to get those neurons to reconnect.

What they did is very smart, but surprising. They performed brain surgery on the patient, removed the olfactory bulb from his brain and took out the cells that allow olfactory neurons to regrow. There was no guarantee when they placed the bulb back that the patient would regain his sense of smell. Surprisingly, he did.

They also used a piece of a nerve from the leg to create the bridge over the gap in the spinal cord. And – once again, very smartly – placed the olfactory cells on the ends of the nerve. That stimulated the axons – or pathways – to grow across the bridge. The use of his own cells and nerves prevented inflammation because the immune system did not perceive any foreign cells in the body.

The problem that I see is that this patient is the first one. We cannot know if this will help others. There are also some inconsistencies in the data of the report, such as the distance of the scar. After six months, the gap in the cord is actually bigger than it was – twice the distance, in fact. That does not match the fact that the patient’s motor control has improved. So one wonders if the person is improving spontaneously. You can regain some motor function after severing with the same training the patient has been doing.

There is a doubt we will ever see full recovery with this method. What doctors saw is an improvement of the motor function and sensory improvement – the person can start to gain some feeling and have some movement. That is an amazing achievement, especially because it can mean so much to a patient who has lost all feeling.

This is an incredible achievement. Whether it can be duplicated is a question. In the past, studies that used animals with the same procedure were half successful and half not. Perhaps a combined approach of using cells already in the spinal cord plus ones from the olfactory system might yield better results.

So I’m hopeful, but carefully hopeful.