It is now over twenty years since Jennett and Plum in 1972 coined the name “persistent vegetative state” to describe a state that is 'neither unconscious<ness> nor coma in the usual sense of these terms... <but rather> wakefulness without awareness”. (1) It is a term that has been widely used since, and the mantraps and spring guns that were built into the definition at the outset are still dangerous. Definitions decided on at the outset have channelled the debate ever since, and are still influential. It is important to re-examine the first steps in this area to see why that course was adopted then and why it is still directing us now.

 

Jennet and Plum noted in 1972 that new methods of treatment were permitting the survival of patients with devastating brain damage resulting from such insults as head trauma, brainstem stroke, or hypoxia - conditions that would previously have resulted in rapid death. They saw this situation as creating a need for a new term.

 

 

A situation, however, is not necessarily the same thing as a condition, and the situation could have been given a name that did not bring it within the medical diagnostic framework. The contribution of Jennet and Plum was to ensure that the “conditions that were formerly fatal” were henceforward to be in practical terms one condition, or one state, and not many.

 

The defintion was a response to a perceived need for simplicity.

 

     There is clearly need for an acceptable term to describe their state, in order to facilitate communication, between doctors or with patient”s relatives or intelligent laymen, about its implications. (Jennett & Plum, 1972, p. 734)

 

This might be taken as begging the question, in that it assumes the existence of the common 'state' that the article argues for. There are, Jennet and Plum point out, a large number of pathways into PVS - head trauma, stroke, hypoxia - and a large number of possible brain states that produce it - damage to the cortex, the brainstem, or the basal ganglia. It is not necessarily obvious that all these would produce an identical 'state'. It will be noted also that the definition is driven initially by the need to communicate between parties, and that this need operates prior to the collection of data - before the observation of common features in the patients with these differing lesions that might provide evidence for the existence of a syndrome. There is from the outset some pressure for there to be a definable syndrome rather than undifferentiated chaos, or even multiple possibilities. If a number of people with different conditions were to prove to be surviving in a large number of different and not necessarily related states that would have to be described individually, this would complicate, rather than facilitating, communication; more than one term would be needed to describe them, and the burden of explanation would increase.

 

The feature of the new condition of PVS that was particularly stressed by Jennet and Plum was that patients were not aware.

     In our view the essential component of this syndrome is the absence of any adaptive response to the external environment, the absence of any evidence of a functioning mind which is either receiving or projecting information, in a patient who has long periods of wakefulness. (Jennett & Plum, 1972, p. 736)

The authors were conscious of the difficulties of providing external proof of internal mental states. Qualifications appear throughout the article; "as best as can be judged behaviourally", for example, the cerebral cortex in these patients was not functioning. One problem is that at the margin the behavioural characteristics that denote consciousness are minute. The authors were in fact particularly concerned to differentiate the condition from locked-in syndrome, named by Plum and Posner in 1965, which is a “tetraplegic, mute but fully alert state” where patients are entirely awake, responsive, and sentient, although the repertoire of response is limited to blinking, and jaw and eye movements. (Jennett & Plum, 1972, p. 736)

 

If

then

      Few would dispute that in this condition the cerebral cortex is out of action. (Jennett & Plum, 1972, p. 734)

 If the eyes, however, blink on order, then the cerebral cortex is not out of action. The ability to control one muscle is decisive. A number of questions thus arise.

 

There are medical conditions that affect eye control; could these be combined with locked-in syndrome to produce a presentation identical to PVS? There are conditions that involve only intermittent eye control; can we be sure that the doctor will be at the bedside at the applicable time?

 

An extensive set of physical signs are said to prove cortical dysfunction; one further observation, that of purposive eye movements, does not modify or add to the diagnosis but rather overturns and reverses it completely; how much weight can we under these circumstances attach to the claimed undisputed consensus? Jennett & Plum go on to discuss specifically the issue of behavioural imputations of consciousness.

 

     ....there is a group of patients who never show evidence of a working mind. This concept may be criticised on the grounds that observation of behaviour is insufficient evidence on which to base a judgement of mental activity; it is our view that there is no reliable alternative available to the doctor at the bedside, which is where decisions have to be made. (Jennett & Plum, 1972, p. 737)

 

The reasoning embodied in this paragraph deserves close attention. Decisions have to be made, they say, and must be made on the available evidence, however inadequate. One response might be to ask what decision the doctor is making at the bedside. What actions are to depend on a diagnosis of unconsciousness? First, however, we must note that Jennet and Plum are not at the bedside, and that a decision to incorporate unconsciousness into a clinical definition may require other arguments than practical necessity. It is surely illegitimate to reason, as here, that 

     - we have insufficient evidence to make a judgement;

 

     - but we must make a judgement; therefore

 

(and this term in the argument is implied only)

 

     - we must have sufficient evidence,

 

and therefore

 

     - we do have sufficient evidence.

 

If observation of behaviour is in fact insufficient evidence on which to base a judgement of mental activity, then it surely remains insufficient whatever the demands made on the individual practitioner.

 

This form of argument by oxymoron occurs elsewhere at crucial points of the article. Jennet and Plum are clear that PVS must be sharp-edged - present or absent, not present to a greater or lesser extent. They criticise the term 'apallic syndrome', previously sometimes used as a description of post-coma unresponsive states, because in that formulation 'partial and incomplete syndromes are admitted'.

 

     Although we would not deny that a continuum must exist between this vegetative state and some of the others described, it seems wise to make an absolute distinction between patients who do make a consistently understandable response to those around them, by word or gesture, and those who never do. (Jennett & Plum, 1972, p. 737)

 

The form of reasoning here is similar;

 

     - a continuum exists between PVS and locked-in syndrome;

     - but we must make an absolute distinction between PVS and locked-in syndrome;

therefore (an implied term)

     - there is not a continuum between PVS and locked-in syndrome, but rather an absolute distinction.

 

The need, moreover, was for the identification of a state that was not only clearly differentiated but irrecoverable.

 

     Certainly we are concerned to identify an irrecoverable state... (Jennett & Plum, 1972, p. 734)

 

The problem was that at the time of writing the article Jennet and Plum were unable to do this with confidence in any given case; reliable diagnosis of a 'permanent vegetative state' was admittedly beyond them.

 

 

The degree of caution expressed here does not, however, extend into their definition. Rather than removing the element of prognosis from the definition, Jennet and Plum rather keep the predictive function and look to further research to remove their difficulty.

 

     Exactly how long such a state must persist before it can be confidently declared permanent will have to be determined by careful prospective studies. (Jennett & Plum, 1972, p. 737)

 

They do not contemplate the possibility that uncertainty as to prognosis may be inherent in the condition, and that future experiment may simply document the persistence of this uncertainty.

 

It is only here, moreover, that Jennet and Plum refer, even by negation, to the other control group relevant to the diagnosis of PVS. Some patients with the characteristics of PVS instead have locked-in syndrome, and this is relevant to the degree of reliance that can be placed on the diagnosis; some other patients with the same characteristics recover consciousness (and a smaller number recover function), and this is still more relevant. This is the group where differential diagnosis would be particularly significant, and where it cannot be offered. The only means, then and now, to distinguish people with persistent vegetative state from people with merely transient vegetative state is to observe them and see whether their vegetative state persists; the longer it persists, the higher the probability that it will continue. Why are the qualities of absence of consciousness, clear differentiation, and established irrecoverability so important that normal canons of reason must be stretched to accommodate them?

 

To answer this question we must return to the situations in which Jennett and Plum foresaw the new term being useful. Firstly, there is the need to facilitate communication with the relatives of the patient. One topic on which discussion might take place is covered elsewhere in the article.

 

     A significant grasp reflex often appears, and this may be provoked by chance touch of the bedclothes; to the inexperienced observer or hopeful family the resulting movement may look as though it was initiated by the patient and may even be regarded as purposeful or voluntary. (Jennett & Plum, 1972, p. 734)

 

If there is dispute between hopeful families and professionals it may well be useful to be able to refer to a diagnosis that excludes hope. If, contrariwise, the family wish to believe that the patient is not suffering, then that, too, can be more easily dealt with by a clear statement that he or she can, by definition, feel no pain.

Secondly, there is the need to facilitate communication between doctors and intelligent laypeople. What, then, is to be discussed in this context?

 

     It may well become a matter for discussion how worth while life is for patients whose capacity for meaningful response is very limited.... (Jennett & Plum, 1972, p. 737)

 

Plainly, ethical questions involving the possibility of terminating that life are expected to emerge. These questions would be greatly simplified if it were possible to establish on the evidence three of the propositions at issue - that people in this state had no consciousness, that the state could be reliably diagnosed, and that it was irrecoverable.

 

     If it were possible to predict soon after the brain damage had been sustained that, in the event of survival, the outcome would be a vegetative mindless state, then the wisdom of continuing supportive measures could be discussed. (Jennett & Plum, 1972, p. 737)

 

If it was not possible to establish these three propositions reliably from the available evidence, and Jennet and Plum concede that it was not, then it might be of assistance if they could instead be smuggled into the debate by being incorporated into the definition of PVS; and this Jennet and Plum virtually do.

 

Jennet and Plum's initiative fell on fertile ground. Their seminal article is given credit in virtually every subsequent piece in the expanding debate on the definition of life. Like many medical references, they are doubtless cited more often than they are read. They have, nonetheless, succeeded in fixing the terms of subsequent ethical debate. A typical recent article on the ethics on withdrawal of life support (2) describes PVS as a condition where

 

     patients are considered to have permanently lost the function of their cerebral cortex. ... All voluntary reactions or behavioural responses reflecting consciousness, volition or emotion at the cerebral cortical level are absent. ...there is no observable experience of pain or suffering. ... They remain permanently unaware...

a formulation that incorporates all three of the suggested simplifications.

 

PVS is not an irreversible condition; anything up to 58% of patients recover consciousness (3). Despite improvements in technology since 1972 it remains conceptually impossible to establish that any person unable to communicate does not feel pain; it is instructive to know, however, that people with locked-in syndrome do feel pain (4), and it is perhaps instructive that people who have recovered from PVS have apparently never been asked whether they felt pain or not.

Similarly, there are no studies of the reliability of the diagnosis of either PVS or locked-in syndrome, although estimates of incidence varying from '1% to 12% of those in coma for more than 24 hours' (5) do suggest some differences in interpretation. The prospective studies that Jennet and Plum's article calls for have never been done.

 

Despite these practical difficulties, Jennet and Plum's definition, along with its conceptual baggage, still effortlessly dominates the field, and its incorporated assumptions are almost invariably taken as axiomatic. The general and continuing acceptance of their sleight of hand indicates that the social needs identified and embodied in the original article still retain their influence on our culture.

 

Jennet and Plum's propositions are not, of course, ethically determinative of many of the issues that arise in the area. Questions of the right to life, or the right to die, will arise whether or not consciousness is present, whether or not the condition is permanent, and whether or not diagnosis is reliable. The questions of resource allocation, of substituted judgement, of quality of life are not, or at least not entirely, dependent these factual substrata. One can rationally decide that care should be withdrawn from such people whether or not they will eventually demonstrate consciousness, and one can even decide that if they are paralysed but aware then their situation is worse and their need for release more persuasive. Debate over the right of persons in this situation to choose death, in particular, would be given new urgency if we were to explore their communication more closely.

 

Whether or not the eventual decision, or the eventual outcome, would be different, however, it would still be unethical to take that decision or to reach that outcome on the basis of an unquestioning acceptance of possibly dubious factual propositions, and we must in any discussion ask ourselves whether our ethical judgements would be different if these propositions were mistaken. If any element of our decision does rest on claims of fact, we have a responsibility to examine their truth or falsity without reference to the need to spare either the feelings of families or the reputations of doctors.

 

 

Andrews, K., 1993, Patients in the persistent vegetative state; problems in their long-term management, British Medical Journal, 306, 1600-2

 

Jennet, B., & Plum, F., 1972, Persistent Vegetative State After Brain Damage; A Syndrome in Search of a Name, Lancet, April 1, 1972

 

Levin HS, Saydjari C., Eisenberg H, Foulkes M., Marshall R., Ruff R., et al, 1991, Vegetative state after closed head injury, Archives of Neurology 48, 580-5

 

Mitchell, K., Kerridge, I., & Lovat, T., 1993, Medical futility, treatment withdrawal, and the persistent vegetative state, Journal of Medical Ethics, 19, 71-76

 

 

1 Jennet & Plum, 1972

 

2 Mitchell, Kerridge, & Lovat, 1993

 

3 Levin et al, 1991

 

4 Jennet & Plum, 1972

 

5 Andrews, 1993

 

Republished with thanks from the Monash Bioethics Review, 1995, 14, 2, 20-26.

Borthwick, C., Persistent vegetative state; a syndrome in search of a name, or a judgement in search of a syndrome?