A car crash victim has spoken of the horror he endured for 23 years after he was misdiagnosed as being in a coma when he was conscious the whole time.

Rom Houben, trapped in his paralysed body after a car crash, described his real-life nightmare as he screamed to doctors that he could hear them - but could make no sound.

'I screamed, but there was nothing to hear, ' said Mr Houben, now 46, who doctors thought was in a persistent vegatative state.

'I dreamed myself away,' he added, tapping his tale out with the aid of a computer.

Doctors used a range of coma tests before reluctantly concluding that his consciousness was 'extinct'.

But three years ago, new hi-tech scans showed his brain was still functioning almost completely normally.

Mr Houben said: 'All that time I just literally dreamed of a better life. Frustration is too small a word to describe what I felt.'

'Medical advances caught up with him,' said Dr Laureys, who believes there may be many similar cases of false comas around the world.

The disclosure will also renew the right-to-die debate over whether people in comas are truly unconscious. 

Mr Houben, a former martial arts enthusiast, was paralysed in 1983. 

Doctors in Zolder, Belgium, used the internationally accepted Glasgow Coma Scale to assess his eye, verbal and motor responses. But each time he was graded incorrectly.

Only a re-evaluation of his case at the University of Liege discovered that he had lost control of his body but was still fully aware of what was happening.

He is never likely to leave hospital, but as well as his computer he now has a special device above his bed which lets him read books while lying down.

Mr Houben said: 'I shall never forget the day when they discovered what was truly wrong with me - it was my second birth.

'I want to read, talk with my friends via the computer and enjoy my life now that people know I am not dead.'

Supporters of euthanasia and assisted suicide argue that people who have lain in persistent vegetative states for years should be given the opportunity to have crucial medical support withdrawn because of the 'indignity' of their condition.

But there have been several cases in which people judged to be in vegetative states or deep comas have recovered.

Twenty years ago, Carrie Coons, an 86-year-old from New York, regained consciousness after a year, took small amounts of food by mouth and engaged in conversation.

Only days before her recovery, a judge had granted her family\'s request for the removal of the feeding tube which had been keeping her alive.

In the UK in 1993, doctors switched off the life support system keeping alive Tony Bland, a 22-year- old who had been in a coma for three years following the Hillsborough disaster.