Is Superman kidding himself?

The face is familiar, but the expression is weirdly bright, almost ecstatic. The eyes have a manic intensity, the skin is taut and the smile takes no prisoners. Here is a living head on a useless body that may soon, if you believe in miracles, be useless no longer.

It is seven years since Christopher Reeve, the actor most famous for playing Superman, was paralysed in a fall from his horse. Since then, he has devoted his life, and a considerable part of his fortune, to trying to repair his body and campaigning for more research into spinal cord injury. He has hired doctors and therapists, invested in exercise machines and electrical stimulation devices and investigated umpteen new treatments, from the orthodox to the outlandish. Over the past three years, he has spent £857,000 on an "activity-based recovery programme". Last week he claimed it had worked.

A home video shot by Reeve's son Matthew suggested the most famous quadriplegic in the world (with the possible exception of the scientist Stephen Hawking) had made a remarkable recovery. He had begun to wiggle the toes on his left foot and to move the fingers on his left hand. Sensation was returning, he said. He could feel the difference between hot and cold, sharp and dull, and he could detect a pinprick anywhere on his body. Best of all, he could feel the his family's hugs. "To be able to feel the lightest touch, it's really a great gift," he said. "The fact is that even if your body doesn't work the way it used to, the heart and the mind and spirit are not diminished. It's as simple as that."

On the face of it, this is impressive. Reeve's doctors describe it as remarkable. But when one looks back to what he was saying five years ago, it appears less so. In an interview with CBS's 48 Hours in May 1997, Reeve reported that sensation was returning to his arms, hands and "all the way down to the base of my spine, which is really a breakthrough because six months ago I couldn't feel down there". For the first time since his injury, he told the interviewer, he could feel the touch of his son Will, then aged five. "I can feel his arm on mine. The thing I want more, though, is to put my arm around him. That's what he is entitled to. And I believe that day is coming."

So the grim reality is that, in five years,Reeve has progressed from feeling the touch of his son on his arm to wiggling his toes. For the man who pledged he would be walking by the time he was 50, a landmark he passes this month, "recovery" seems an inappropriate word.

His physician, Dr John McDonald of the Washington University School of Medicine in St Louis, was cautious last week, while trying to avoid outright pessimism. "Any recovery brings some hope with it. How much is the question ... it is a big deal in the world of neurosurgery and neurology that he has had any recovery at all ... [but] the likelihood of Chris walking again is still something we don't know, and I don't want people to get the impression that, boy, we are making some breakthrough here."

There lies the dilemma for the treating physician – how to sustain the patient's will to live in the face of a devastating injury with the gloomiest prognosis. There are an estimated 50,000 people paralysed by spinal cord injuries in the UK, and 250,000 in the US. The most public of them is renowned for his determination – the home video was televised as part of a series called Christopher Reeve: I will walk again. One of his doctors, Harlan Weinberg, once said the actor had "an incredible inner strength and more personal drive than any individual I have ever met".

But the unpalatable fact is that, if recovery has not happened in the first six to 12 months after a severe spinal cord injury of the kind Reeve suffered, significant progress in subsequent years is not just unlikely, but unheard of.

Tony Tromans, senior consultant in the spinal injuries unit at Salisbury District Hospital, Wiltshire, said: "The likelihood of Reeve getting back on his feet and walking is remote. I have had patients who have learnt to flicker their fingers five years after an injury but even if you start training them, it doesn't progress beyond non-functioning movement. The majority who are going to get back on their feet do so in six months."

There is another factor behind Reeve's extraordinary optimism – money. Medical research consumes vast amounts of cash and people are likely to give only if they feel there is some likelihood of progress. Reeve has been a tireless campaigner on behalf of the scientific community, which in turn has kept the hopes of donors high with a sustained flow of scientific studies suggesting that the lame may be made to walk again soon.

Last week, Reeve sent a message of support to the UK Medical Research Council as it announced details of the first stem-cell bank, which is due to open next year and will provide researchers with the mother cells from which nerve cells and other organs may be regrown. "I'm extremely grateful that the UK has wisely chosen to proceed with Government funding and oversight," he said. "Without the courage of scientists who refuse to take the easy, less controversial path, we would not have made so many major medical breakthroughs throughout our history."

It would be a brave scientist who countered such enthusiasm by telling him it could take decades for the work to bear fruit. The regeneration of the spinal cord is being researched across the world, and a number of groups have reported promising results with mice and rats. Dr James Fawcett, chairman of the scientific committee of the UK charity Spinal Research, said three treatments had proved successful in animal experiments which had the potential partly to repair spinal cord injuries. "When these treatments are applied to patients with high-level neck injuries, like that sustained by Christopher Reeve, it could transform their quality of life." But even eager proselytisers such as Dr Fawcett admit that a cure is a distant prospect. Clinical trials of the new treatments are not expected to start until 2005, and the results will not be available for years after that.

A major problem is that the higher up the animal order from mice to humans, the shorter the distance it has proved possible to get nerves to regrow. Several centimetres of regrowth is very significant in a mouse, resulting in a recovery of the ability to walk after spinal injury in some experiments, but it is much less significant in the larger body of a human being. Even so, research offers the only hope – and preserving hope is one of the tasks of treatment. "If you bash someone's hopes, they will flounder and drown," said Mr Tromans. "On the other hand, if they have got unreal expectations which will never come to fruition, they will also drown. It is a very delicate balance."

Desperate patients will take desperate measures to hang on to hope. Some patients from Salisbury have travelled to the International Spinal Cord Regeneration Center in Tijuana, Mexico, which charges $65,000-$85,000 for embryonic cell transplant therapy from the blue shark. Surgeons from the centre have shown a video of one Salisbury patient to demonstrate the effectiveness of their therapy. But Mr Tromans was unimpressed. "We could have shown an identical video when she was discharged from here. We have had several patients go out there and come back no better, but somewhat poorer."

For Reeve, the task has been to keep living, keep working and, as he put it in an interview in 1999, "not only to recover my body, but to recover a sense of purpose". He tours America tirelessly, disconnecting his ventilator to gulp out a few words, seeking donations for his paralysis foundation. This week, he will be on public platforms again for the launch of his memoir, Nothing is Impossible: reflections on a new life. In the book, Reeve writes: "So many of our dreams at first seem impossible, then they seem improbable and then, when we summon the will, they soon become inevitable. If we can conquer outer space, we should be able to conquer inner space, too."

Biologically, the realisation of his dream of walking again seems a very long way off – but psychologically, the man who once played Superman has already demonstrated the triumph of his seemingly superhuman will.