A year ago, the limp body of the star of the Superman films was wheeled before the Democratic Party convention where, with laboured breaths, he uttered a few words in support of Bill Clinton and received a standing ovation. It was a moving moment. The celebrity who personified superhuman strength had been physically destroyed but continued to display the extraordinary fortitude associated with his alter ego. It proved that Reeve was more than a class act.
Now, in an interview broadcast in the US last night on CBS's 48 Hours programme, Mr Reeve has confounded his doctors by reporting that sensation is returning to his arms, hands and back. He said he had now recovered sensation, apparently through sheer force of will, "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 said, he could feel the touch of his five-year-old son, Will. His greatest wish was to be able to cuddle him. "I can feel his arm on mine. The thing I want more, though, is to be able to put my arms around him. That's what he is entitled to. And I believe that day is coming."
Although it is too soon to say whether he will walk again, his doctors are clearly astounded by his recovery. In most cases of spinal injury, the extent of the damage is clear within two months. It is extremely rare for patients to continue improving after that point.
Dr Harlan Weinberg, one of Mr Reeve's doctors, told the programme of his admiration for the 44-year-old star's courage. "He's very focused. He has an incredible inner strength, and more personal drive than any individual I have ever met. I think that has a lot to do with it."
Another of his doctors, Steven Kirshblum, said: "There are things that aren't supposed to happen ... but sometimes we see miracles."
Such comments suggest that something truly remarkable is happening. But the reality is almost certainly more prosaic. Nor does Mr Reeve himself underplay the mental and physical struggle he faces each day. "What people don't know about is, like, in the morning, when I need 20 minutes to cry, to wake up, to just say 'this really sucks', to really allow the feeling of loss - even two years later - to be acknowledged," he said.
Surprising as his improvement is, it falls a long way short of miraculous. British specialists advised caution in interpreting it as progress towards any kind of cure. Delayed improvement following spinal injuries, although rare, is not unknown. The spinal cord is a bundle of nerve fibres, each of which is comprised of a cell body - the nucleus - and an axon, encased in an insulating sheath, which may be up to a metre long. Although the spinal cord cannot regenerate new cells, if the cell body is still alive it can re-grow a damaged axon.
Sometimes axon re-growth may be physically blocked by the presence of scar tissue. Even if there is no physical barrier, scar tissue may restrict the blood supply to the insulating sheath, preventing sufficient oxygen reaching the axon to allow re-growth.
In rare cases, however, there may be a slow improvement in the blood supply and in the supply of oxygen, allowing further re-growth, which in turn brings the slow return of sensation and movement. This may be what is happening to Christopher Reeve.
Achieving significant late recovery is, however, very unusual. "In nine years, I have never seen a case myself," says Dr Tony Tromans, director of the spinal injuries unit at Odstock hospital, Salisbury, one of the leading centres in the UK. The hospital treats 70 new cases of spinal injury a year, and Dr Tromans says that he has seen in addition "a couple of thousand" chronically injured patients in that time.
"I would be very pessimistic about the improvement Mr Reeve reports being a sign of purposeful recovery. I would be fairly doubtful that he will acquire more feeling, or be able to breathe independently or be able to move his limbs. He will probably always be dependent on a ventilator. Any more optimistic comment runs the risk of sowing false hope."
Dr Tromans says that sensations going down the middle of the back below the point of the injury, as described by Mr Reeve, are not uncommon. It is unclear whether he can properly feel his son cuddling him or whether he simply has an awareness of his presence through the weight of his body.
His capacity to do without a ventilator could also be exaggerated. In the US, specialists train patients in an exercise known as frog breathing, in which they are taught to gulp air. Ten gulps is equivalent to a reasonable breath, which must then be repeated 10 times a minute.
"After 20 minutes you feel fairly knackered. It is very encouraging to do, because it means you can breathe on your own if the ventilator fails, but you can't keep it up for long," Dr Tromans says.
The patient's attitude is crucial, not in altering the basic biology, but in making the most of improvements that do occur. Positive thinking cannot make nerves re-grow, but it can ensure that the maximum benefit is drawn from whatever recovery is achieved at the biological level.
"If you are completely fed up, you will turn your face to the wall and die. But no matter how strong and positive you are, you cannot make nerve damage recover. On the other hand, if you are not positive, you cannot take advantage of any recovery that does occur."
The patients who cope best are those who, like Stephen Hawking, the scientist and author, get on with their lives in spite of their disabilities. Mr Reeve recently made a TV film about Aids, and has been suggested for the starring role in a planned remake of the Alfred Hitchcock classsic Rear Window, about a man confined to a wheelchair who sees a crime committed in an apartment opposite his own.
"Some people give up their interests and focus on overcoming their disabilities," Dr Troman says. "It is better to focus on carrying on with life, because there is a risk of falling flat on your face if you fail to overcome your disabilities. I don't like saying that people have to come to terms with them - why should they? - but can they keep the struggle up for ever?"
Research is under way into new drug treatments to promote healing of spinal injuries. Known as nerve growth factors, they have been shown in the laboratory to stimulate nerve re-growth, but human trials are still some years away. Peter Banyard, research director of the International Spinal Research Trust, says that three techniques are currently being tested. "There is hope for these patients, but they may be too late to help Christopher Reeve".