• vegetative state
• minimally conscious state
• neuropathology
• cortical function
• legal aspects

In the 30 years since this state was first described and named¹ it has provoked intense debate not only among clinical scientists and health professionals but also among moral philosophers and lawyers. Considering its relative rarity there is also, courtesy of the media, an unusual degree of public awareness of the condition. What attracts attention and curiosity is the dissociation between arousal and awareness—the combination of periods of wakeful eye opening with lack of any evidence of a working mind either receiving or projecting information. The advantage of the term “vegetative state” is that it simply describes observed behaviour, without implying specific structural pathology. However, since the realisation that this state is frequently temporary, the original term persistent vegetative state is potentially misleading as it suggests irreversibility. After a certain length of time it may none the less be reasonable to describe this state as permanent.²

Before specific diagnostic criteria were agreed, some reports had used less rigorous definitions.³ The most widely accepted criteria are those in the 1994 report from the US Task Force.⁴ These are essentially negative—the lack of evidence of awareness of the self or the environment, of interaction with others, or of comprehension or expression of language. By implication, external stimuli do not evoke purposeful or voluntary behavioural responses that are sustained and reproducible. There are two problems in applying these criteria. One is the wide range of reflex responsiveness in some vegetative patients, some of which can give rise to suspicion of meaningful mental activity. The other is the limited range of voluntary responses available to severely brain damaged patients, which can make the detection of awareness difficult.⁵ The recent publication of detailed …