Inside, Mr Invisible screamed but no one could hear

There had never been anything unusual about Martin Pistorius — until he came home one day, complaining of a sore throat. It was January 1988.

He was 12 years old. He would never go back to school.

From that day onwards his body gradually ceased to function. He forgot facts. His muscles started to waste away. His hands and feet curled in on themselves like claws. His weight fell and he had to be spoon-fed. He stopped responding, and his parents and younger brother and sister watched him slip away.

He wasn’t paralysed, because his body moved, albeit uncontrollably, but it seemed that his brain had gone too. After a year of assorted treatments, doctors in his native South Africa declared that he had some kind of degenerative neurological disorder. There was no known cause and nobody imagined he would ever recover.

Still today, nobody knows the cause or long-term prognosis. But what has happened to Pistorius in the years after his decline has the potential to teach us a huge amount about human endurance and raises profound questions for anybody who ever felt that a reduced life was “not worth living”.

Pistorius’s mother gave up work to look after him and over the years his father too would give up on promotions and opportunities in order to do the same. Round-the-clock care proved too much for Pistorius’s parents and after a year he was put into daycare. But even so, his mother spiralled into depression and one night tried to kill herself by taking pills. She was taken to hospital just in time.

Years passed and around the age of 16, Pistorius’s mind started to come back. By 19 it was more or less fully functioning. But nobody noticed … for another six years.

Having been told that his brain was damaged, nobody imagined that his intelligence might be intact. They saw only a young man with stick-like limbs, empty eyes and drool running down his chin. Thus, though he was by now in his early twenties, Pistorius was parked for days on end in front of Teletubbies.

People would speak in front of him as though he couldn’t understand. At a family party one relative said: “Look at him. Poor thing. What kind of life is that?”

Others did much worse. When his family went on holiday, he was left to stay overnight at a residential care home, sometimes for weeks at a time. He was frequently abused. So-called carers would shovel food into his mouth that was burning hot. “Eat it, you f****** donkey,” one used to say. Once, when he threw up, she shovelled the vomit onto the spoon and made him eat that. He would be left to chill after baths, or parked under the blazing sun. Others interfered with him for their own sexual gratification.

Unable to tell anybody what was happening, Pistorius was horrified to hear his mother trying to persuade his father that their son would be better off in that residential home permanently. Mercifully, his father wouldn’t budge and Pistorius stayed in daycare, where he was bored but not violated.

Over the years he saw many carers come and go, and noted the puzzlement and revulsion with which many of them studied him. But one day a physiotherapist arrived to give him an aromatherapy massage. Virna van der Walt was not like the rest.

She talked to Pistorius as if he really could hear. He tried to let her know that he understood. She told others, who were sceptical, but his parents took him to a specialist who confirmed it by asking him to make specific eye movements and enter into a kind of rudimentary dialogue. Suddenly, his life started again. His muscle control improved a little, and with an electric wheelchair he could get about on his own.

His voice never came back, but by using an assortment of aids he was even able to communicate.

There was no stopping him. His parents helped to program words into his communications software and were astonished that he understood a wide vocabulary. They began to understand, with horror, how badly they — and everyone else — had underestimated him.

He discovered a natural understanding of computers and was soon given work in the care centre’s offices, for a day a week. Encouraged to adopt a more professional appearance, and confident that he would no longer dribble, he gave up the bib.

Human relations remained complicated, because “speaking” through gadgets presents unusual problems, as I discovered when I met Pistorius, now 35, at his publisher’s offices recently. He was smartly dressed and had a firm handshake with a spark in his eye as he smiled a greeting. On his lap, he had a robust keyboard with a tiny LED screen, through which he communicated by typing. (Speaking machines such as the one used by Stephen Hawking are prohibitively expensive.) He uses only his right hand, which flutters rapidly over the keys, but even short answers take some time.

“A conversation with me is slow,” he says. “People find the silence so hard, they often don’t talk to me. If they do, they must make a conscious effort to look at me and listen to what I have to say. I can’t butt in. I’m not nearly as talkative as I once thought I would be.”

Slow delivery isn’t the only issue. “My words will never quaver with emotion, rise expectantly for a laugh just before a punchline, or drop dangerously in anger,” he says in his book. Nor does he always get the chance to talk: people sometimes approach him, and when he starts typing, they think he’s being rude and walk off. One eight-minute “speech” took him 40 hours to input.

Perhaps inevitably, Pistorius fell in love with the kindly physiotherapist. She thought she saw his feelings in his face and asked if she’d understood correctly — then firmly told him they could only be friends. “My smile set in my face like concrete,” he remembers, “then finally shattered. I could feel a pain in my chest: heartbreak.”

To her credit, they did remain friends. Pistorius made others too, and with their help gradually got to know the world. One, Erica, took him to McDonald’s and to shopping centres and cooked biscuits for him.

His parents bought him a dog, which learnt to recognise non-verbal commands. “Raising my fist to my chest told Kojak to sit down.”

As a young man he was never going to be satisfied with the companionship of a dog — but perhaps the biggest miracle is that he does not need to be satisfied, because he found a wife.

A few years ago Pistorius was talking on Skype to his sister, who had come to work in Britain as a social worker. She introduced him to a fellow South African, Joanna, who worked with her. Joanna was friendly, paid careful attention to Pistorius’s typed dialogue and subsequently contacted him directly. They began to communicate a lot.

Then one day she said she was going on a trip to the US and asked Pistorius whether he would like to go with her.

He was astonished, overwhelmed. “Why do you want to meet me?” he asked.

“Because you’re the most honest man I’ve ever met,” she replied.

He decided to be perfectly clear. Without help, he told her in a starkly honest email, he could not get in and out of a shower, use a knife and fork, shave himself, do up his shoelaces, buttons, zips or get on and off the lavatory. Immediately she replied that this didn’t matter.

Joanna seemed too good to be true. Pistorius’s parents worried she might let him down; even her friends were sceptical, saying it was cruel to let Pistorius think they might have a life together.

As it happens, they never made it to the US, but Pistorius came to visit Joanna here (he didn’t eat or drink for 11 hours beforehand, to be sure he wouldn’t spill anything and arrive looking a mess).

On that visit, in 2008, Joanna immediately started learning to recognise letters as Pistorius formed them on her hand, or leg: that way he could communicate while she drove, on their trip around the country.

One day, to express his thanks, Pistorius made Joanna breakfast. It was the first time he’d ever done anything like it, and his shaking hand scattered coffee and sugar all over the floor and smeared jam across the table. She didn’t seem to mind but told him she loved him.

They married in 2009. “I lived my whole life as a burden,” he says. “She makes me feel weightless.”

Ghost Boy is published by Simon & Schuster at £14.99