He was undergoing radical and invasive surgery to implant electrodes in his brain in the hope that the tiny electrical current they generated could neutralise the shaking.

As the surgeon pushed the tiny probe ever deeper, Robins saw flashing lights.

He lost his ability to speak — for just a few minutes. Then the surgeon hit the spot.

“Suddenly, for the first time in seven years, the shaking stopped,” said Robins. “Despite all the risks, the surgery had worked. You cannot believe the relief I felt.”

The operation, in 1999, was a triumph. But his return to good health came at a price, £12,000, and recently tremors have appeared on the other side of his body, meaning he will need a second operation.

What if there were a better way, a cure that could replace the damaged cells inside the patient’s brain? And what if it could be applied to other conditions as diverse as diabetes, heart failure and spinal paralysis? Christopher Reeve, the paralysed Superman actor who died last week, believed a new technology called stem cell therapy was the answer.

Was he right? Have scientists discovered a panacea that will not only cure some of mankind’s most debilitating illnesses but also get paraplegics walking again? Until a few years ago such hopes seemed pure fantasy, but scientific discoveries in the 1990s showed that stem cell therapy could be successful. The principles are simple.

Stem cells are biological blank slates. They come in two main types: adult and embryonic. It is the embryonic stem cells that are causing most excitement, because in theory they can be turned into any one of the 220 types of tissues in the human body.

In the normal process of an embryo’s development, this process occurs naturally. In stem cell therapy, the idea is to control it artificially to produce specific tissues. Then they could be used to replace cells damaged by disease or accidents. Stem cells have already been used to regrow damaged spinal nerves in rats.

Reeve did not live long enough to see this treatment used on humans. But his death coincided with two developments which suggest that his hopes are close to fulfilment, using both “natural” stem cells and manufactured ones.

New Scientist magazine devoted five pages to TriStem, a British start-up company that claimed it had rescued patients from “the brink of death” by creating personal stem cell therapies using no more than a blood sample.

ReNeuron, another British company, announced last week that it was ready to start the world’s first clinical trials with manufactured stem cells. It wants to inject them into the brains of stroke victims with the aim of replacing damaged tissues and restoring lost functions such as walking, talking and eating.

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