Persistent Vegetative State

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Persistent vegetative state (PVS) was identified by that name in 1972 by the neurologists Bryan Jennett and Fred Plum (Jennett and Plum 1972). Both the name and the state have been a source of controversy since that time.

General Description

PVS results from the total lack of function of the cerebral cortex, the large outer part of the human brain. The size of the cortex in different species of vertebrates correlates with their respective levels of intelligence, with primates having the largest cortex among all genera and humans having the largest among all primates. Cortical activity is necessary for all types of cognitive states, from sight and hearing to speech and thought. The most common causes of loss of cortical function are traumatic injuries and anoxic-ischemic injuries. Traumatic injuries include those seen in car or motorcycle accidents, and anoxic-ischemic injuries include those seen in strokes, drowning accidents, and cardiac arrest, in which there is a loss of oxygen (anoxia) or blood flow (ischemia) to the brain. Either cause can lead to the same outcome, but because that outcome occurs by different routes, there are some distinctions in the diagnostic criteria.

Whether the origin of a brain injury is traumatic or anoxic-ischemic, the initial result of a severe injury is a coma. Patients in a coma look as if they were asleep, although they never open their eyes or have sleep-wake cycles. In fact, they are not in a sleeplike state but are deeply unconscious, as is evidenced by the fact that they cannot be awakened by even the most painful stimuli and do not exhibit reflex responses to such stimuli. However, comas are usually a temporary stage of response to injury. Generally a patient is in a coma for no more than two weeks. After that time coma patients progress to one of three alternatives: They regain consciousness, die (most commonly as a result of swelling of the brain that causes herniation of the brain stem and loss of brain stem function), or enter a vegetative state.

Some patients improve after emerging into a vegetative state. They subsequently may regain a normal level of consciousness or improve slightly and enter a minimally conscious state. However, the longer they remain in a vegetative state, the less likely it is that they will ever improve. Thus, a PVS is defined as having been in a vegetative state for a length of time that makes further improvement highly unlikely. If the cause is anoxicischemic, in which case there is a fairly uniform causal pattern of neural death, one needs to wait three months to make the diagnosis. If the cause is trauma, which has greater variability of intermediate causes of neural death, one needs to wait a year to achieve the same degree of certainty and thus make a diagnosis of PVS. The exact location of the blow, the degree of force, and even factors such as the condition of the brain and the skull at impact can be variables in the degree of brain damage.

The Concept of Vegetative

Why is the term vegetative used? In the classic terminology dating back to Aristotle humans are defined as uniquely rational, with emotional (or irrational) traits being shared with animals. Purely physiological functions such as digestion are called vegetative; they are neither rational nor irrational, and they have nothing to do with social interaction at any level. It is only these physiological functions that are preserved in patients in whom the brain stem is the only surviving part of the brain.

Therefore, in contrast to cases of death diagnosed by brain criteria, the vegetative state is characterized by the presence of all brain stem functions (autonomic nervous system regulation of body temperature, pulse, blood pressure, breathing, reflexes, and sleep-wake cycles) without any of the cortical functions. Thus, most or all brain stem reflexes typically are intact in PVS patients: cold calorics (cold water in the ear canal causes lateral eye movement toward that ear), papillary (response to light), corneal (light tough of the eyeball causes a blink), threat (a quickly approaching object causes blinking), gag, and painful stimuli (usually a sternal rub or pressure on the fingernail beds causes withdrawal). For all these reasons the verbal slip of calling a PVS patient brain-dead is a mistake that threatens family members' trust in doctors and other health-care professionals.

Although the definition of PVS is made clinically, that is, empirically, it is possible to use neuroimaging techniques such as computed tomography (CT) scans, functional computed tomography (FCT) scans, and positron emission tomography (PET) scans to build confidence in the prognosis at an earlier time. In cases such as an observed loss of oxygen for thirty minutes or when there is a loss of cortex replaced by cerebrospinal fluid that is documented on a CT scan, experienced neurologists may feel confident in making the diagnosis of PVS in less than the three or twelve months recommended in the American Neurological Association Task Force report (American Neurological Association 1993). For some families that do not want to wait, this can be very helpful. However, others may feel rushed and may become skeptical if they discover that the neurologist is making a diagnosis sooner than is recommended in the consensus statement.

Causes of PVS

The largest numbers of cases of PVS are caused by anoxic-ischemic injuries, and this diagnosis has increased in frequency. This is the case because it takes only four or five minutes without oxygen for a patient to begin to have permanent brain damage in the cortex, which requires very large amounts of oxygen. However, the inner parts of the brain, the brain stem and midbrain, require less oxygen and can return to function after much longer periods of oxygen deprivation. (One might picture the cortex as a softball wrapped around the golf ball–sized brain stem.) Thus, anything that causes the loss of some or all oxygen to the brain for more than five minutes may lead to PVS. The most common cause of that loss occurs when a patient "codes," that is, when the patient's heartbeat or breathing stops.

Why is this cause the source of a growing number of cases of PVS? In the United States and many other countries after the invention of cardiopulmonary resuscitation, it became routine for all patients to be "full code" unless they specifically requested otherwise. When a patient is discovered unconscious as a result of acute loss of cardiac or pulmonary function, a "code" is begun, starting with clearing the airway and beginning chest compressions and ending with cardioversion/defibrillation and endotracheal intubation and mechanical ventilation. The code ends either when a heartbeat is restored or when the physician who is running the code decides to "call" it (that is, to call an end to the code), which will be the time when death is declared.

A code typically is run for thirty to forty-five minutes. However, it is up to the physician, using clinical judgment, to determine how long to wait before calling, or ending, a code. In light of the nature of the brain, if a pulse does not return after fifteen to thirty minutes, there is the risk of permanent brain damage, including global loss of cortical function. The length of time a code is run cannot be determined precisely to avoid all cases of PVS because there is usually some oxygen going to the brain during the code as a result of the chest compressions applied by the physician. However, because of the nature of cardiopulmonary resuscitation (CPR) as an acute and heroic effort to save a life that is being lost, it is antithetical to try to "call" codes more conservatively to minimize the number of cases of PVS at the cost of not maximizing the number of lives saved.

In contrast, the number of cases of PVS resulting from trauma has decreased as a result of the greater use of seat belts and air bags in cars and the wearing of helmets by bicyclists and motorcyclists. There is no registry of patients in PVS, and so the number cannot be known with any degree of certainty. The most common guess is that there are 10,000 people in the United States in a PVS, although the number could be half or twice that.

Ethical Issues

The ethical issues raised by PVS are as complex as the neurology is. For example, three of the most publicized and controversial cases in medical ethics involved young women who were in a PVS: Karen Ann Quinlan in New Jersey in the 1970s, Nancy Cruzan in Missouri in the 1980s, and Terri Shiavo in Florida in the early 2000s. In each case the patient's family wanted to make the decision to stop life-sustaining treatment once their loved one's grim prognosis became evident.

At least two factors make decisions regarding PVS patients very difficult. First, observing these patients is an unnerving experience: Although awake during the day, they have some movements of the arms, back, neck, and head, including grimaces and smiles, and make sounds such as moans and grunts. This makes it almost inevitable that the family will have doubts about the diagnosis and about whether the patient may show improvement eventually. Second, although these patients require extraordinary around-the-clock nursing care to avoid bedsores and infections, they need relatively little medical intervention except a feeding tube to provide artificial nutrition and hydration. If this care is provided and the occasional infection is treated with antibiotics, PVS patients can haveanormal lifespan. Thus,somehavebeen keptalive for three or four decades. These two factors make it very difficult for families to stop the life-sustaining treatment for patients in a PVS even when they are confident that the patient would not want to live in such a condition.

When these issues first were addressed by the bioethics community in the 1980s, many people argued that feeding tubes and artificial nutrition and hydration should be considered a necessary component of humane treatment and be required to demonstrate respect for human dignity, comparable to being kept clothed and given some privacy. This view has become less common but still is held by some theologically oriented bioethicists in the Roman Catholic and Orthodox Jewish traditions. Support for the position that artificially provided nutrition and hydration constitutes necessary medical treatment was called into question as the nature of PVS became understood and, simultaneously, the hospice movement began to promote the idea of death with dignity. Although it still is not universally accepted, there is a broad consensus among clinicians, lawyers in the field of health law, and ecumenical and secular bioethicists that artificial nutrition and hydration should be consented to or refused on the basis of an evaluation of its benefits and burdens to patients on a case-by-case basis.

This is the ultimate controversy regarding PVS: determining how a patient would want to live. Perhaps the best philosophical clarification of the issue came when James Rachels (1986) summed up the sentiment that family members of PVS patients had expressed by saying that the life of PVS patients was over years before they died. Rachels distinguished between life in a biological sense and life in a biographical sense; put more colloquially, PVS patients no longer "have a life" even though they are still alive. Thus, the use of a living will or an advanced medical directive may be the only way to determine how a patient would want to be treated if found in a persistent vegetative state.

In light of the controversy surrounding PVS, it is clear that some medical conditions are not as easy to manage as others. Although the definition of PVS is relatively straightforward, the ethical issues are not. PVS continues to be an area of much debate, both ethically and legally, and the issues surrounding it are not easy to resolve. Because of this PVS will continue to be researched and discussed to help ease the discomfort involved in making decisions about patients in a persistent vegetative state.


SEE ALSO Bioethics; Brain Death; Medical Ethics.


American Neurological Association Committee on Ethical Affairs. (1993). "Persistent Vegetative State." Annals of Neurology 33(4): 386–390. A succinct summary of both the clinical and ethical issues raised by PVS.

Brody, Baruch. (1992). "Special Ethical Issues in the Management of PVS Patients." Law, Medicine, and Health Care 20(1–2): 104–115. Discusses a wide range of ethical issues, including futility and the just allocation of resources.

Childs, Nancy L., and Walt N. Mercer. (1996). "Brief Report: Late Improvement in Consciousness after Post-Traumatic Vegetative State." New England Journal of Medicine 334(1): 24–25. There have been a few reports of improvement of patients in PVS such as this case.

Jennette, Bryan, and Fred Plum. (1972). "The Persistent Vegetative State after Brain Damage: A Syndrome in Search of a Name." Lancet 1: 734–737.

Lynn, Joanne, ed. (1989). By No Extraordinary Means: The Choice to Forgo Life-Sustaining Food and Water. Bloomington: Indiana University Press. A collection representing both sides of the debate on whether medical provision of nutrition and hydration through invasive procedures should be considered optional life-sustaining medical treatment or ethically required humane treatment. Much has been written since, but this may have appeared just at the point in the history of the debate when the tipping point was reached and a new consensus was developed.

Multi-Society Task Force on PVS. (1994). "Medical Aspects of the Persistent Vegetative State." New England Journal of Medicine, Part I: 330(21): 1499–1508; Part II: 330(22): 1572–1579. This report by the American Association of Neurology (AAN) and the American Academy of Neurology (ANA) defines the current standard of practice.

Rachels, James. The End of Life. Oxford: Oxford University Press, 1986. Chapter three, "Death and Evil," includes his famous distinction of biological versus biographical life, and other interesting observations on the conceptual and ethical problems that result when a life lacks the proper elements of a narrative.

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Persistent Vegetative State


A PVS usually occurs within one month after an acute traumatic or non-traumatic brain injury and evolves from a coma to a state of sleep-wake cycles without awareness. Loss of ability to control bladder and bowel function is present.


Individuals in a persistent vegetative state (PVS) have sustained injury resulting in a loss of higher brain functioning including thinking abilities but breathing and circulation are intact. Individuals in a PVS do not speak and cannot respond to commands. Individuals in a PVS do have variable reflexes but show no evidence of purposely responding to stimuli.


About 10,000 to 25,000 adults and 10,000 children in the United States are diagnosed as being in a PVS.

Causes and symptoms

The most common cause of PVS is traumatic brain injury resulting in oxygen deprivation but any condition resulting in brain damage can result in a PVS. Some adults and children progress into a PVS as a result of degenerative and nervous systems disorders. Some infants are born with congenital deformities of the nervous system that result in a PVS.

The individual in a PVS shows no awareness of self or the environment and there are no purposeful responses to stimuli or commands. There is no language comprehension or expression. Some reflex activity is present. Sleep-wake cycles do occur but may not be rhythmic. Bladder and bowel incontinence is present.


Diagnosis is usually made by the presence of characteristic findings obtained by observing the individual. Imaging studies by computerized axial tomography (C.A.T.) scan and magnetic resonance imaging (M.R.I.) may be used to rule out treatable conditions and confirm a diagnosis of PVS. PET Scans (Positron Emission Tomography) and SPECT scans (Single Photon Emission Computed Tomography) are more sophisticated types of nuclear imaging that use radioactive material to evaluate functioning of an organ. PET and SPECT scans may be done if there is doubt regarding a diagnosis of PVS.


Once any acute conditions, if present, are treated the focus is on providing supportive care and preventing infection. Infection is the most common reason for death for someone in a PVS. Medical and nursing care is targeted at maintaining nutrition and preventing complications related to immobility e.g., pneumonia , urinary tract infections, bedsores, and blood clots .


  • What is a persistent vegetative state?
  • How long will the condition last?
  • What type of treatment is needed?
  • What is the prognosis for recovery?

Nutrition/Dietetic concerns

During a PVS, the ability to chew and swallow in a normal way is lost because these actions are voluntary. Nutrition and hydration may be provided by artificial means either intravenously or through a feeding tube into the stomach.


Supportive medical and nursing care must be provided. The individual in a PVS requires frequent repositioning and daily skin care, including bowel and bladder hygiene, to prevent bedsores. Antibiotics may be necessary to treat frequent infections e.g., pneumonia and bladder infections. A tracheostomy may be necessary to maintain adequate breathing. Feeding tube placement is usually necessary to maintain adequate nutrition and hydration. Physical therapy may be initiated to prevent the limbs from contracting.


Most individuals die within six months of the original brain injury and for most of the others, life expectancy is approximately two to five years after the injury. The chance of recovery from a PVS is generally higher if the brain injury is the result of a traumatic injury (like a blow to the head) than they are for non-traumatic injury (such as a stroke ). The chance of recovery decreases the longer the individual is in a PVS. Chance of recovery is not likely after one month for a non-traumatic injury and after 12 months if the damage is traumatic. Even if recovery occurs after these time periods, most individuals are severely disabled. The degree of recovery, if it occurs, varies and if recovery does occur, it is usually very gradual. Chance of recovery may be higher for younger individuals and children.

Caregiver concerns

Family members are often called upon to make decisions regarding the amount and level of treatment that will be administered or withheld for an individual in a PVS including medication, oxygen, dialysis, blood, and artificial nutrition and hydration. Family may also be involved in the decision on whether or not to implement a “Do Not Resuscitate” (DNR ) order if the patient has no advance directive.

June G. Borazjani R.N., M.S.N., C.P.H.Q.

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Persistent Vegetative State

Individuals in persistent and permanent vegetative states (both called PVS) are not dead, although philosophers still debate whether they are "people." Their brains still function at a very rudimentary level; they have sleep-wake cycles; and they normally can breathe without assistance. According to the American Academy of Neurology, about 10,000 to 25,000 PVS individuals exist in the United States at any one time. Approximately 50 percent of them have been in this state less than six months and 70 percent for less than a year.

People go into PVS after their brains suffer a lack of oxygen, a lack of sugar, or a similar event. Normally, the onset of a coma is the first stage. If they neither die nor awaken, they lapse into a "vegetative state." Usually, only young trauma victims awaken from this state; older or oxygen-deprived individuals, which is the more common situation, usually do not. After one month health practitioners call the condition a "persistent vegetative state." If their brain damage is the result of a non-traumatic event, adults and children rarely emerge from a persistent vegetative state after being in it for three months. If the damage results from trauma, children rarely recover after being in the state for one year; adults rarely emerge after six months in that state. At some indeterminate time later, the patient's condition transforms into an irreversible "permanent vegetative state."

Physicians with training and experience in PVS make the diagnosis on clinical grounds established by the American Academy of Neurology, which include:

  • no awareness of themselves or their environmentan inability to interact with others;
  • no reproducible, purposeful, or voluntary responses to visual, auditory, tactile, or noxious stimuli; and
  • no ability to speak or to understand language; sleep-wake cycles with intermittent wakefulness without awareness; sufficiently preserved lower brain and brain stem functions to permit survival with medical and nursing care; bowel and bladder incontinence; variably preserved cranial nerve (pupillary, oculocephalic, corneal, vestibulo-ocular, gag) and spinal reflexes.

No diagnostic study can make the diagnosis with certainty. Except in the case of infants with anencephaly, reliable criteria do not exist for making a diagnosis of PVS in infants less than three months of age.

The American Academy of Neurology states that of the adults in a persistent vegetative state for three months after brain trauma, 35 percent will die within a year after the injury. Another 30 percent will go into a permanent vegetative state, 19 percent will recover with severe disabilities, and 16 percent will recover with a moderate or minimal disability. If they remain in a persistent vegetative state for six months, 32 percent will die, 52 percent will go on to a permanent vegetative state, 12 percent will recover with severe disabilities, and 4 percent will recover with moderate or minimal disability. Nontraumatic brain damage markedly decreases the chance of any recovery. After such patients have been in PVS three months, only 6 percent will recover with severe disabilities and 1 percent will recover with a moderate or minimal disability. After six months, no adults who remain in that state recover.

Children have a better chance of recovering from brain trauma than adults. Virtually all children in a persistent vegetative state from causes other than trauma go on to a permanent vegetative state rather than to death. Unlike adults, about 3 percent of these children recover, but always with severe disabilities.

Medical experts differ in opinion as to exactly how those in PVS should be classified. These individuals cannot interact with or experience their environment, feel pain, or communicate in any waytheir thinking, feeling brain is gone. Their condition will not improve, but they can live with medical and nursing support for many decades.

See also: Cruzan, Nancy; Do Not Resuscitate; End-of-Life Issues; Life Support System; Quinlan, Karen Ann; Resuscitation


American Academy of Neurology Quality Standards Sub-committee. "Practice Parameters: Assessment and Management of Patients in the Persistent Vegetative State." Neurology 45 (1995):10151018.

Iserson, Kenneth V. Death to Dust: What Happens to Dead Bodies?, 2nd edition. Tucson, AZ: Galen Press, 2001.

Iserson, Kenneth V. Grave Words: Notifying Survivors about Sudden, Unexpected Deaths. Tucson, AZ: Galen Press, 1999.


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persistent vegetative state (PVS) (per-sist-ĕnt) n. the condition of living without consciousness or the ability to initiate voluntary action, as a result of brain damage. People in the vegetative state may sometimes give the appearance of being awake and conscious, with open eyes, but there is no response to any form of communication and no reason to suppose that there is any awareness of the environment. Medical treatment may be legally withdrawn from a patient in PVS but permission must first be granted by the courts. Compare locked-in syndrome.

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persistent vegetative state: see under coma, in medicine.