David Mzee was paralyzed for seven years until one of Switzerland's leading neurosurgeons gave him a spinal implant that changed his life. He is one of three patients with spinal cord injuries who are now able to walk again with targeted electrical stimulation of the spinal cord, scientists announced Wednesday.

"This little device that is an impulse generator is giving impulses to the electrode that is located on the spinal cord," Dr. Jocelyne Bloch, a neurosurgeon at Lausanne University, told CBS News.

A paper published this week in the journal Nature details how the device works.

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Spinal cord injuries disrupt communication within the nervous system, which leads to the loss of neurological functions and paralysis. Normally, nerves in the spinal cord send signals from the brain to the legs. However, in someone who is paralyzed, the signal sent is usually too weak to create movement. The implant boosts the signal activating muscles in the legs.

The patients control the stimulation remotely through a watch. When it's on, Mzee is able to walk more than half a mile using a walker or crutches for support.

"I think you have to try and do the impossible to make the possible possible – and I think we're doing that and it feels good," he said.

David Mzee walks after receiving a spinal stimulation implant. CBS News

The scientist who developed the technique says the implant even seems to help repair damaged nerves.

"Nerve fibers are growing again. They are reconnecting the brain to the spinal cord," Professor Gregoire Courtine of the Swiss Federal Institute of Technology told CBS News.

Doctors are working to make the stimulation more comfortable for patients like Mzee so they can keep the device active all the time.

Scientists say the research shows that paralysis can be reversed to some degree, though the question remains how much.