The Royal College of Physicians said that it would welcome any clinical information with a bearing on the guidelines surrounding the condition, which is usually thought to be irreversible after a year.
The doctors and parents of 30-year-old Hillsborough victim Andrew Devine, from Allerton, near Liverpool, confirmed that five years after the football disaster, he had recovered sufficiently to communicate simple ideas.
The case is significant because doctors have never before recorded a case in which anyone regained the ability to communicate after more than three years in such a condition. Medical guidelines say that doctors can apply to a court to have a patient's food and hydration withdrawn after 12 months.
Mr Devine's parents, Stanley and Hilary, speaking through their solicitor, Robin Makin, yesterday said: "Andrew began to emerge from the vegetative state about five years after his diagnosis [in 1989] and has continued to improve in his ability to communicate at a simple level, using a touch- sensitive buzzer switch developed by the Royal Hospital [for Neurodisability in south London].
"His ability to recover further is unknown. Andrew's condition is of the utmost seriousness and he needs constant attention. Andrew has a civil claim against the Chief Constable of South Yorkshire Police, in respect of which judgment has been obtained but damages have still to be assessed and no further information can be given in respect to this matter.
"A proper care regime, including substantial physiotherapy, has been involved to ensure that Andrew has the best care reasonably available."
Mr Makin, of the solicitors E Rex Makin and Company, from Liverpool, added that his parents had given Andrew devoted love and care.
Dr Keith Andrews, director of medical and research services at the Royal Hospital for Neurodisability, where Mr Devine has been regularly assessed and treated, said yesterday that although his improvement had been limited, he had been able to communicate a few simple ideas. "We recognised back in 1994 that there were signs that he was becoming aware. It was only last year, that we got him communicating consistently."
He was able to reply to questions by pressing the buzzer once for yes and twice for no. "He expressed which football team he supported. One of our therapists asked him: `Is Manchester the best football team in the country?' He answered no. The same happened when she asked about Everton. But when she asked: `Is Liverpool the best team?' Andrew answered yes.
"When we first told Andrew's carers that we thought he was responding, they were not convinced at first. We were only able to prove that he could because of our expertise and technology," he said.
Dr Andrews, who caused a furore last summer when he showed that some cases of persistent vegetative state (17 out of 40 in his study) had been wrongly diagnosed and that several patients who had thought to be vegetative could actually communicate, believes that Mr Devine's state is due to a genuine improvement, not to an original misdiagnosis. There are thought to be between 1,000 and 1,500 people in a PVS in Britain.
"For someone to emerge from a PVS after five years as Andrew has done is pretty remarkable. We have treated a large number of people, who have not come out of such states even after a long time. The longest time after which anyone has ever emerged from a vegetative state before has been three years. It is rare to emerge from such a state after a year," he said.
"You cannot make decisions on such rare cases. If it occurs only once in 10,000 cases, you have got to give some consideration to the other 9,999 cases. Are you respecting them by continuing to do absolutely everything for them, such as putting up drips and so on, just because one person has managed to emerge."
A spokesperson for the Royal College of Physicians, which last year issued guidelines telling doctors how to recognise PVS, said: "The college would welcome any new clinical information being sent to them, which has a bearing on the guidelines."
The parents of Tony Bland, the Hillsborough victim whose family won the right from the House of Lords to withdraw his life support in 1993, said yesterday that the development in the Devine case did not affect the case of their son, who had a particularly severe case of PVS, and they had "no regrets".
States of unconsciousness
No awareness of self or environment; eyes open and shut, as though awake and asleep; can breathe normally; most have to be fed through a tube.
No verbal response; cannot be roused; does not obey commands or open eyes either spontaneously or to any stimulus; must be fed through a tube. Can regain consciousness after many months.
Patient is conscious and aware of surroundings, but is totally paralysed, and can usually only respond by eye movements.
Damage to the brain is irreversible. Patient is unconscious and unable to breath without a ventilator.