One of Helen Thwaite's most valued possessions is a small attache case in which she keeps her 'coma kit'. It contains some feathers, a whistle, a small bottle of whisky, smelling salts, blocks of wood, mirrors and shiny, coloured holograms.

Ms Thwaite, an occupational therapist at the Royal Hospital and Home for Incurables in Putney, London, uses this motley collection in her work with coma patients, some of whom are described as being in a persistent vegetative state (PVS). This is a condition in which patients permanently lose the function of their cerebral cortex, usually through head injury. They can breathe unaided, are fed through a nasogastric tube and intravenous drips, and spend long periods with their eyes open. But they can produce no voluntary activity or any meaningful response to the environment, beyond reflex reactions to light or pain stimuli.

There are an estimated 1,500 PVS patients in Britain. They present a major moral dilemma for the health service. Last week, doctors in Yorkshire said they are considering an approach to the High Court for permission to disconnect feeding tubes and allow Tony Bland, 21, a Hillsborough victim, to die. Mr Bland is a PVS patient and his parents have repeatedly asked that he be allowed to die with dignity. But the law is unclear. Doctors fear they may be prosecuted for murder if they withdraw food and water. A test case would help clarify a difficult ethical question.

Others take a different view. Dr Keith Andrews, director of medical and research services at the Royal Hospital and Home, which is a charity and not part of the NHS, says that the term PVS is unfortunate. 'Most people understand it to mean permanent - a final outcome rather than a comment on the present state,' he says. In addition, vegetative implies vegetable-like. 'Neither of these interpretations encourages a positive approach to treatment. It is a self-fulfilling prophesy. If people are never expected to get better then they never will.'

He points out that in one study of 84 PVS patients, 34 became aware by six months, a further 10 by one year and another five by three years. There are reports in the medical literature of improvement after five years, and one recent unconfirmed report from Australia of awareness returning after seven years.

Dr Andrews believes that patients' potential for recovery is hindered by the treatment they receive once doctors decide a patient is in a PVS, and by the shortage of facilities for their care. Putney is the only specialist rehabilitation unit in the United Kingdom for PVS patients; most health authorities are at a loss to know what to do with the two or three who may be in their care. They may languish for up to six months in the general ward to which they were first admitted.

As a result, more than 80 per cent of PVS patients are undernourished when they are eventually admitted to a rehabilitation unit. They are usually constipated, suffering muscular contractures, and have been lying looking up at a ceiling. 'It is not surprising that the brain is not functioning properly under these circumstances. We get the nutrition right, then their bowels and bladders,' Dr Andrews says.

Then the patients are put through a coma arousal programme, developed by the hospital in conjunction with researchers at Surrey University. Ms Thwaite and her colleagues work to stimulate the patient and return them to awareness. The success rate is low - about 50 per cent - and progress is slow. No one knows if they would have improved by themselves anyway. The patients who do regain consciousness will remain severely physically and mentally disabled, but Dr Andrews believes that the effort is worthwhile. 'Every patient in a PVS should be given a chance as early as possible to go through a full rehabilitation programme.'

The programme begins with an intense observation period to give staff a baseline to measure the patient's progress by. They concentrate on visual and auditory functions - touch, smell and taste, and grade the patient's response, if any. The therapist then concentrates on developing the best responses.

Stimulation takes place in short bursts of a minute or so, followed by a 15-minute rest. 'Few healthy people can cope with lengthy periods of intense concentration, and brain-damaged patients can concentrate for only 15 seconds at a time,' Ms Thwaite says.

The therapist will also research the patient's background, talking to families and friends about their special interests. One patient, Roger, had been a perfumer, and the staff used different fragrances in their work with him.

This makes their work more poignant, Ms Thwaite says, because 'we are seeing them as they are and not as they were.' The patients range in age from late teens to old age; many are the victims of road accidents. 'We get bikers, and a few skiers; many were wild-living and obvious risk-takers, but there are lots of (car and bike) passengers, too.' The pressures on the relatives of these patients cannot be overestimated. 'They have to contend with someone who is living but who is not with them,' Dr Andrew says.

The work is gruelling and the rewards are few, but when there is a change, a response, however gradual, it is a 'miracle', Ms Thwaite says. One of the unit's successes is Rosie Johnson, 26, who received devastating brain injuries in a road accident four years ago. She was a violinist with the Welsh National Opera Orchestra, and tipped for a successful career. After the accident she was in a coma for seven months.

Ms Thwaite remembers her progress: 'Rosie didn't respond at all at first, there was nothing. Then we began to get eye contact, then she would discriminate between two objects, and eventually she was choosing what she wanted to wear, and began to vocalise.' Rosie now lives with carers in Hounslow, Middlesex.

There are 40 beds in the brain injury unit at the hospital, and half of them are occupied by PVS patients. They will remain in the unit for up to nine months as doctors decide what progress has been, or is likely to be made. Dr Andrews is realistic. 'You sometimes ask yourself if it is worthwhile given that the success rate is low, but we are reassured by the small number who do show some recovery and some quality of life. They can enjoy their friends and family, their environment and music.

'We don't know why some recover and others don't. If the brain was so simple that we could understand it then we'd be so simple that we could not.'

(Photograph omitted)