Evolution News and Views (ENV) provides original reporting and analysis about the debate over intelligent design and evolution, including breaking news about scientific research.

Evolution News and Views

Terri Schiavo and the Persistent Vegetative State

This is the first in a series of posts in which I will discuss the medical and ethical aspects of persistent vegetative state (PVS). As I noted in an earlier post, I believe that the emergence of PVS as an accepted medical diagnosis is in part a consequence of the emergence of strict materialistic theories of the mind in the late 20th century, especially the theory called "functionalism," which is the theory that the mind is what the brain does, in the same way that running a program is what a computer does. If the mind is entirely caused by the brain, in a way analogous to the running of a software program on a computer's hardware, it stands to reason that there would be situations in which damage to the brain would cause the "mind program" to irreversibly crash. This leads to rather obvious ethical implications. Ideas have consequences, and the materialist understanding of the mind has had direct and disturbing consequences for the medical treatment of people handicapped by severe brain injuries. I will explore this connection between philosophy of the mind and clinical medicine in a future post.

PVS came to wide public attention with the death in 2005 by dehydration and starvation of Terri Schiavo, a young woman with severe brain damage caused by a cardiac arrest (probably from an electrolyte imbalance) in 1990. She died because her feeding tube was removed by court order at the request of her husband, who claimed that she had told him that she would have wanted to be deprived of nourishment under these circumstances. The deprivation of water and nourishment to a handicapped person, even with the pretext of accommodating that person's wishes, obviously raises ethical issues, and I'll discuss them in future posts. I'll address primarily the medical and neurological issues in this post.

The first question to ask is this: what do we mean by "consciousness"? What we commonly understand as "consciousness" has two components: arousal and cognitive content. Arousal merely refers to the appearance of wakefulness. The eyes are open, the person may move in various ways, etc. Cognitive content refers to the subjective (first-person) aspects of the mind, such as perceptions, thoughts, beliefs, desires, intentions, etc. These subjective states have been called "intentional states," and intentionality is a hallmark -- really the hallmark -- of a conscious mind. In this sense, it should be noted that sleep isn't really unconsciousness. We don't show arousal (our eyes are closed, etc), but we can have intentional states (in a dream, we can have fears, hopes, beliefs, etc.). The mind is still working, even in sleep.

Coma is a rather vague term, referring to the initial loss of arousal after an injury to the brain. In actual medical practice, it is often defined according to the Glasgow Coma Scale, a measurement of mental status developed several decades ago to provide accuracy and consistency in the evaluation of patients with altered mental status. It consists of examination of motor response (following commands, flexing the arms, etc.), verbal response (talking, grunting, etc.), and eye opening (spontaneous, only to noxious stimuli, etc). "Points" are assigned to each category. The most total points a patient can get is 15; the least, 3. Coma is generally defined as a Glasgow Coma Score of less than 8. It is important to note that the assessment of coma is all behavioral. We have no access to other peoples internal mental states except by behavior -- movement -- of some sort. Our diagnosis of coma depends entirely on the ability of a patient to communicate through movement in some fashion. The diagnosis of coma is unreliable in direct proportion to the impairment of the patient's ability to move and communicate.

Coma, understood as a lack of arousal, is always temporary. It has long been recognized that all brain-injured people, even those who are initially in deep coma, will eventually (after several weeks or months) exhibit arousal. They will open their eyes, have sleep and wake cycles, and appear to be alert. Most people go on to improve more, often completely, but some continue in some form of this "vigilant" state indefinitely. These states of vigilance vary considerably from person to person, but they often show little external evidence of cognitive content -- of an internal mental state. Decades ago, these eclectic conditions were called various names: "coma vigil," "akinetic mutism," and "apallic syndrome." Sometimes people would, in time, wake up from these states. I've seen a number of patients wake up after six months or a year; the longest duration of coma vigil with subsequent recovery that I've seen was four years. The patient, a young man with a head injury from a car accident, woke up rather suddenly one night and began talking quite coherently and asking about his family. I was the resident on call, and when the nurses told me, I thought it was a practical joke. The patient made a good recovery. However, such recovery from several years of unresponsiveness is uncommon.

In the mid 20th century, the medical description of prolonged lack of apparent conscious content following brain injury was a bit eclectic. In 1972, neurosurgeon Bryan Jennett and neurologist Fred Plum suggested the use of the diagnostic term "persistent vegetative state" (PVS) to describe these various states of absence of discernable cognition. PVS incorporated the earlier diagnoses of "akinetic mutism," etc. Jennett and Plum suggested that central to the diagnosis of PVS was a wakeful unconscious state -- "wakefulness without awareness," which is arousal without cognition. PVS was the diagnosis that a brain injured patient had motor functions such as eye opening, non-purposeful movements of limbs, etc., but she didn't have cognitive content, such as perceptions, beliefs, desires, etc. Succinctly, she had a body and a (damaged) brain, but no mind.

The diagnosis of PVS became widely used, although the diagnostic criteria varied a bit, and in 1994 a Multi-Society Task Force made up of representatives of the American Academy of Neurology, the Child Neurology Society, the American Neurological Association, the American Association of Neurological Surgeons, and the American Academy of Pediatrics produced a Consensus Statement on the medical aspects of PVS. The criteria for the diagnosis were:

The vegetative state can be diagnosed according to the following criteria; (1) no evidence of awareness of self or environment and an inability to interact with others; (2) no evidence of sustained, reproducible, purposeful, or voluntary behavioural responses to visual, auditory, tactile, or noxious stimuli; (3) no evidence of language comprehension or expression; (4) intermittent wakefulness manifested by the presence of sleep-wake cycles; (5) sufficiently preserved hypothalamic and brain-stem autonomic function to permit survival with medical and nursing care; (6) bowel and bladder incontinence; and (7) variably preserved cranial-nerve reflexes (pupillary, oculophalic, corneal, vestibulo-ocular, and gag) and spinal reflexes..... A wakeful unconscious state that lasts longer than a few weeks is referred to as a persistent vegetative state.

Note two things critical to this diagnosis: first, objective ancillary tests such as CT, EEG, and MRI are not part of the diagnostic criteria. The diagnosis is established by bedside examination. Ancillary tests are of some help in confirming the presence of severe brain damage, but this is usually obvious from the context. Ancillary tests have no direct bearing on the diagnosis of PVS as currently defined.

Second, and of great importance, is the fact that all of the diagnostic criteria for PVS are behavioral, in the sense that the diagnosis depends critically on the ability of the patient to communicate his internal mental state. Paralysis and muscle incoordination intrinsically diminish the reliability of the diagnosis.

In the media and even among physicians PVS is often confused with other conditions such as brain death. Here's a list of neurological conditions that can be confused with PVS:

Brain death
Brain death is biological death of the entire brain. There is no movement (except for spinal reflexes), no breathing, no eye opening. There are no brain waves, and there is no blood flowing to the brain. The heart may beat and some of the body organs may work, but the entire brain is biologically dead. All patients who are brain dead must be maintained on a respirator if the heart is to be kept beating.

In the United States, brain death is legally the same as death. Brain dead people are dead. Organs may be removed for transplantation, and the body may be removed from the ventilator.

Terri Schiavo wasn't brain dead, or even close to it. Brain death has nothing to do with PVS.

As noted above, PVS is a state of arousal without awareness. It is, in a sense, "mind death," in that the brain is still biologically alive but there is no evidence of subjective mental processes. In this sense, PVS eliminates the personhood of the patient, because the property of "personhood" necessarily implies intentions, beliefs, will, etc. An entity without a mind cannot be a person in any meaningful sense. PVS is the only medical diagnosis that alters the personhood of a patient.

Because the identification of a mind in a brain-damaged person depends entirely on behavior, the very brain damage that raises the question of PVS diminishes the reliability of the exam that would establish the diagnosis.

PVS cannot be diagnosed in a person who, due to damage to motor systems necessary for purposeful movement, cannot communicate.

Minimally Conscious State
Minimally conscious state (MCS) is a recent addition to the diagnosis associated with brain damage. MCS is essentially "PVS except...". It is a state of severe brain damage in which there is some small but clear evidence of mental processing. As with PVS, it is not clear how much of the apparent loss of evidence for mental processing is due to actual loss of mental processing and how much is due to impairment of communication -- motor behavior -- due to profound brain damage.

Locked-in state
Locked-in state is a profound paralysis of all muscles except the muscles that control vertical movements of the eyes and sometimes blinking. It is usually due to a stroke in the pons. Patients are often mentally normal. Their only method of communication is blinking and vertical eye movements. They can signal yes and no to questions.

If the examiner does not notice the eye movements, or if the patient does not realize that he can communicate this way, the patient would be indistinguishable, on bedside exam, from a patient with PVS.

As noted above, coma is a rather vague term meaning loss of arousal. It too is diagnosed entirely by behavioral criteria, usually using the Glasgow Coma Scale, as discussed above.

Cerebral palsy
Cerebral palsy is a generic term for congenital and non-progressive brain injury, often caused by cerebral hypoxia/ischemia (lack of oxygen and blood flow to the brain). People with cerebral palsy have predominately motor disability ("palsy" means paralysis). They have varying degrees of paralysis, spasticity, chorea, athetosis, and ballismus (the last three are involuntary movements associated with the brain damage).

There is generally relative preservation of cognition; many people with cerebral palsy are intellectually normal, and some are quite bright. It is often difficult to assess their mental state, because of their profound difficulty in communicating. They frequently cannot speak, and purposeful movement is very difficult.

Many educational strategies, using computers and other aids, have allowed people with cerebral palsy to communicate very well and to enjoy an education and a rich social life.

The closer one examines the diagnostic issues involved in PVS, the more clear it is that PVS is in many ways a problematic diagnosis. The diagnosis of PVS relies entirely on the patient's ability to communicate internal mental states to the examining neurologist. Yet severe brain damage intrinsically limits the patient's ability to move and speak. Patients in whom the diagnosis of PVS is made are precisely those people in whom the assessment of mental state is most unreliable.

Furthermore, PVS is the only medical diagnosis that, by denying that the patient has a mind, denies the personhood of the patient. Thankfully, many people in PVS are still treated with respect as persons by their families and caregivers, but that respect is conferred despite, not because of, the diagnosis of PVS.

My interlocutor on this topic, Yale neurologist Steven Novella, has posted several essays in defense of what was done to Terri Schiavo. I'll address the issues he raised, such as the reliability of the diagnosis of PVS as well as Ms. Schiavo's autopsy findings and the ethical implications of the deprivation of food and water to people diagnosed with PVS in my next several posts.