The 1994 Multi-Society Task Force consensus statement on the persistent vegetative statement: a critical analysis.

• Author: Howsepian, A.A.

The Multi-Society Task Force (MSTF) on Persistent Vegetative State (PVS) recently released a landmark two-part consensus statement entitled "Medical Aspects of the Persistent Vegetative State," which, in 1994, was published in the New England Journal of Medicine.(1) This statement was approved by the governing bodies of several medical societies, including the American Academy of Neurology, American Neurological Association, American Association of Neurological Surgeons, and Child Neurology Society.

Those who contributed to the drafting of this important document included, among others, an impressive group of neurologists, pediatricians, and neurosurgeons, several of whom have been on the forefront of discussions in the contemporary medical ethics literature concerning the metaphysical and moral status of PVS patients.(2) In spite of their impressive medical credentials, though, and in spite of their many influential contributions to contemporary philosophical and neurological discussions concerning this condition, their present collective effort makes me quite uneasy. The primary source of this unease can be traced to the MSTF's conceptually misshapen defense of the thesis that all PVS patients are unconscious. The MSTF's defense of this thesis is defective in at least two ways. First, the MSTF fails convincingly to motivate the conceptual propriety of utilizing the particular characterization of (un)consciousness that it has, in fact, chosen to employ in this domain. I shall argue, in fact, that the MSTF commits itself to a conception of (un)consciousness that is conceptually incoherent. Second, I shall argue that even if the MSTF were to adopt a coherent and plausible conception of consciousness (and of cognition more generally construed), it has thus far given us no good reason to think that all PVS patients lack consciousness so construed. I further argue that a careful, rigorous analysis of (un)consciousness in the context of this discussion promises to yield those conceptual tools necessary for more precisely delineating the boundary between PVS and the locked-in state, as well as for properly situating akinetic mutism and other intermediate disorders of consciousness on the cognitive continuum that spans the chasm between those paradigmatic states which occupy the polar positions on this continuum.

The perceived dispensability of PVS patients, as portrayed in several recent essays in the medical ethics literature,(3) is typically predicated on the allegedly well-grounded conjecture that all PVS patients are cognitively quiescent. The widespread acceptance of this claim in conjunction with the (to my mind, mistaken) view that to be a live human being is, essentially, to be a member of a specific biological kind which instantiates certain specific, functionally intact, highly complex neuroarchitectural structures, has tempted several thinkers to deny that PVS patients are persons toward whom charity can be properly directed or, in more extreme cases, to deny that PVS patients are live human beings at all.(4) This process of dehumanization has profound, deeply troubling ethical implications-implications regarding which the MSTF is at best neutral and at worst complicit.

What Are the Medical Facts?

The MSTF views itself as simply summarizing "the medical facts about the persistent vegetative state," insisting that "it does not address associated ethical, legal, or other issues."(5) This disclaimer is misleading. In fact, many of the alleged "medical facts" that the MSTF claims to be summarizing really are pieces of quite complex, contentious, and conceptually subtle philosophy. One cannot help but be engaging in a philosophical activity when dealing reflectively with such matters as consciousness, evidence, purposiveness, awareness, irreversibility, and the self.

The MSTF begins its consensus statement by pointing out that "[t]he term `persistent vegetative state' was coined by [Bryan] Jennett and [Fred] Plum in 1972 to describe the condition of patients with severe brain damage in whom coma has progressed to a state of wakefulness without detectable awareness."(6) As it stands, this statement is ambiguous: It could imply that, according to Jennett and Plum at that time, PVS was considered to be a variety of coma which exemplifies as one of its central clinical features signs of wakefulness; or alternatively, that PVS is not a state of coma at all, the presence of wakefulness signaling the emergence of a clinical entity that is incompatible with the proper diagnosis of coma. The MSTF appears to opt for the latter interpretation. Unfortunately, Jennett and Plum were not at all helpful in disambiguating the term that they coined. They stated that the term persistent vegetative state was not intended to refer to a state of "'coma,' as ordinarily defined," for "in particular, it is not a continuation of the coma which characterizes the early stages of these particular patients' clinical course."(7)

At any rate, this progression of coma in severely brain-damaged individuals to states of wakefulness without detectable awareness (however, precisely, this is to be understood) is not, it seems, itself sufficient for the exemplification of PVS, for not just any progression of coma to wakefulness without detectable awareness following severe brain damage could be properly classified as a case of PVS. Status epilepticus involving partial complex seizures can also result in coma which is marked by wakefulness without detectable awareness. And, in fact, it is physically possible that one can enter such a state of status epilepticus from a state of nonstatus coma.

Very early in the consensus statement there occurs a subtle but significant shift in the conceptual direction that the MSTF has chosen to take concerning the role played by (un)consciousness in PVS. The MSTF initially states, for example, that in their seminal 1972 paper Jennett and Plum coined the term persistent vegetative state to describe certain brain-damaged patients who are "without detectable awareness," while later (and, in fact, in the very same paragraph) the MSTF elaborates on this by claiming: "Jennett and Plum thought that patients in a persistent vegetative state could be distinguished clinically from those with other conditions associated with prolonged unconsciousness."(8) There is, of course, a significant conceptual gap between being without detectable awareness and being unconscious. Clearly, being conscious is robustly compatible with being without detectable awareness, while being conscious is incompatible with being unconscious.

According to the MSTF, PVS patients display "no evidence of [i] awareness of self or environment . . . [ii] sustained, reproducible, purposeful, or voluntary behavioral responses . . . [or, (iii)] language comprehension or expression."(9) But, of course, all of this lack of evidence for consciousness is compatible with the presence of consciousness. This point is implicitly acknowledged by the MSTF, for example, when it speaks of the absence of "any behaviorally detectable expression of self-awareness, specific recognition of external stimuli, or consistent evidence of attention or intention or learned responses" in PVS patients.(10) It may be of interest to point out that the aforementioned cluster of symptoms can be accounted for, albeit perhaps less parsimoniously, by a combination of severe, extensive, motor apraxia, agnosia, and hypoactive delirium with an intact, albeit significantly altered, level of consciousness. This possibility is especially relevant given the role that disturbed cortical mechanisms are thought to play in both PVS and in the aforementioned syndromic triad.

Jennett and Plum themselves appear implicitly to allow for the possibility that some persons who the MSTF would classify as PVS patients are, at some level, conscious. This appearance is implicit in the MSTF's restricted appeal to certain behavioral indices--indices that are themselves acknowledged to be compatible with consciousness--as markers for PVS, for Jennett and Plum are clear "not [to] deny that a continuum must exist between this vegetative state and some of the others described [including locked-in state.!"(11) Yet, after having quite carefully stated this, Jennett and Plum then go on to say that "it seems wise to make an absolute distinction between patients who do make a consistently understandable response to those around them, whether by word or gesture, and those who never do."(12) In this manner, Jennett and Plum appear to have taken a default position in this context (for reasons that appear to be related more to clinical expediency than to sound clinical judgment) by their placing within a single nosological category a potentially diverse group of patients based on purely behavioral grounds, while at the same time acknowledging that potential members of this taxonomic category admit of significant cognitive heterogeneity. In turn, the MSTF has also chosen to ignore those conceptual subtleties regarding the possible heterogeneity of mental states exemplified by PVS patients to which Jennett and Plum at least initially appeared to be sensitive.

The Concept of Consciousness Deserves Special Attention

The MSTF's comments on the role that the concept of (un)consciousness plays in discussions concerning PVS deserve special attention. It is initially noted by the MSTF that in 1983 the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research (borrowing from Jennett and Plum) "defined unconsciousness as the inability 'to experience the environment."(13) This definition appears inadequate, for it appears possible both for one to be conscious and, at the same time (i.e., while remaining in the state in question), for one to be unable to experience one's environment. Some persons who are asleep and dreaming, for example, are conscious but, while in that state...