For 23 years, doctors believed a man in Belgium was in a vegetative state, barely able to move or think after a car crash.
Then, doctors studying patients who appeared to be completely unresponsive made a stunning discovery: Rom Houben was in fact awake, CBS reports.
Dr. Steven Laureys of the University of Liege's Coma Science Group, decided to take another look at Houben's brain using the latest imaging technology.
"We put him in the PET scanner, the MRFI," Dr. Laureys told CBS News correspondent Elizabeth Palmer, "and then we saw his brain was functioning normally, so he was not vegetative."
Rom Houben, the victim of a road accident in 1983, was believed to be in a vegetative state but was in fact paralysed and unable to communicate.
The 46-year-old Houben, whose case has made global headlines in recent days, had been conscious for years but unable to communicate or even make known to his carers and family that he was conscious.
The state, which has various levels, is known as "locked-in syndrome" and a recent study carried out in Belgium discovered that doctors get their coma diagnosis wrong "in numerous cases."
The research, by Laureys and others, found that in too many cases poor coma diagnoses were given -- more than 40 percent in certain categories of sufferers.
Former engineering student and martial arts enthusiast Houben told the German weekly Der Spiegel that he had meditated to pass the long years trapped in his own body.
Using a specially-adapted computer to type messages, Houben has been able to describe the ordeal he endured.
"I would scream, but no sound would come out," he said, "I will never forget the day they finally discovered what was wrong -- it was my second birth."
He could hear what was being said around him throughout, but was unable to respond.
"I became the witness to my own suffering as doctors and nurses tried to speak to me and eventually gave up," he said, AFP reports.