The persistent vegetative state

This article was presented in the British medical journal in 1995. It reflects some of the controversy around the definition vegetative and since that date there has been much debate over the reliability and consistency of measurement of an individual’s state of awareness.

Information on prognosis allows decisions to be made on management.

Patients in a vegetative state seem to be awake with their eyes open but show no evidence of awareness. They do not interact with others and make no purposeful or voluntary responses to visual, auditory, tactile, or noxious stimuli. They are able to breathe spontaneously, and they retain their gag, cough, sucking, and swallowing reflexes. Sleep-wake cycles are preserved, and so are the hypothalamic and brain stem autonomic responses. They are incontinent of urine and faeces, but they may retain their cranial nerve, spinal, and primitive reflexes. Inconsistent non-purposive movements occur, notably facial grimacing and chewing; they make sounds; and they may show inconsistent auditory and oculomotor orienting reflexes to peripheral sounds or movement. The diagnosis of a vegetative state is not tenable if there is any degree of voluntary movement, sustained visual pursuit, consistent and reproducible visual fixation, or response to threatening gestures.

The condition is distinct from coma, in which patients have their eyes closed and lack sleep-wake cycles, and from the "locked-in" syndrome, in which patients are aware of themselves and their environment but have lost motor function and speech, communication being achieved by eye movement or blinks. Akinetic mutism is a rare syndrome in which movement is pathologically slowed or nearly absent and speech is lost but wakefulness and self awareness are variably preserved--though the level of mental function is reduced.

Concern about the vegetative state has recently been increased, partly by legal rulings in individual highly publicised cases and partly by professional bodies trying to develop guidelines on its management. In a comprehensive and valuable review the American Multi-Society Task Force on Persistent Vegetative State has summarised published work on the prognosis with the aim of helping a consensus to emerge on management. (Go to international research)

The vegetative state usually develops after a variable period of coma; it may be partially or totally reversible or may progress to a persistent or permanent vegetative state or death. "Persistent" is defined as continuing for at least one month, but this does not necessarily imply permanency or irreversibility. Vegetative states may be caused by acute cerebral injuries, degenerative and metabolic disorders, and developmental malformations. Injuries form the largest and most important group of causes and can be subdivided into traumatic (resulting from road traffic accidents, for example, or direct cerebral injury) and non-traumatic (including hypoxic-ischaemic encephalopathy, a stroke, infection of the nervous system, a tumour, or a toxic insult).

The two dimensions of recovery from vegetative states are recovery of awareness and recovery of voluntary motor function. Recovery of awareness may occur without functional recovery, but functional recovery cannot occur without recovery of awareness. According to the American task force, the most important factors determining the outcome of the persistent vegetative state are the patient's age and the state's aetiology and duration. Overall, the mortality for adults in a persistent vegetative stage after an acute brain injury is 82% at three years and 95% at five years. Death is associated with pulmonary or urinary tract infections, respiratory failure, and sudden death of unknown cause.

The task force estimated the probability of the outcome at 12 months for patients who remained in a persistent vegetative state. Of those adults who remain in this state three months after traumatic injury one third will recover by 12 months, with one fifth of the recovered being severely disabled. After six months in a persistent vegetative state 12% recover to severe disability and 4% to moderate disability or good recovery.

The outcome is worse following non-traumatic insults: after three months in a persistent vegetative state 7% recover, generally with severe disability, and there were no cases of recovery after six months in a persistent vegetative state. The few data on children suggest that the outcome at 12 months of a persistent vegetative state resulting from trauma seems to be better than that in adults but that there is little difference from adults after non-traumatic insults. The task force concluded that a persistent vegetative state can be judged to be permanent 12 months after a traumatic injury and three months after a non-traumatic insult in adults and children. Although an occasional verified recovery has been reported after these times, such recovery is virtually always associated with severe disability.

These findings have practical implications for the management of patients in a coma or a vegetative state after acute brain injury. Aggressive medical treatment is appropriate at the onset, when the prognosis remains uncertain. This will include adequate hydration and nutrition (through a nasogastric tube or gastrostomy), protection of the airway, attention to posture and contractures, and care of the bowel and bladder. Stimulation and rehabilitation should be available as soon as the patient's condition is stabilised, but the place of coma arousal programmes remains uncertain.

Once the diagnosis of persistent vegetative state is established, continuing treatment is justified if, as the BMA's ethics committee states, "it makes possible a decent life in which a patient can reasonably be thought to have a continued interest." The level of treament will depend on the result of clinical assessment by the physician and discussion with the patient's family or other decision makers. The place of high technology treatments (mechanical ventilation, dialysis, cardiopulmonary resuscitation) and routine drugs (such as antibiotics) or other treatments such as supplementary oxygen can be determined only in the context of the individual case.

The BMA has recommended that "if it is apparent at the end of a twelve month period of insentience due to persistent vegetative state that the patient's condition is irreversible doctors will consider whether it is in the patient's best interest to continue with treatment to prolong life." The findings of the American Multi-Society Task Force challenge these recommendations by suggesting that a persistent vegetative state is almost always permanent at three months if the cause was a non-traumatic cerebral insult. Although the evidence is strong, experience (particularly in the subgroups) is not yet still adequate to recommend a change in the British recommendations--but these are currently under review by a working party established by the royal colleges.

Both the medical and the legal authorities have advised that in some circumstances when the patient's condition is irreversible withdrawal of life sustaining treatment, including tube feeding, may be legitimate and ethically acceptable. Such a decision requires independent evaluation of the diagnosis and prognosis, the likely benefits or burdens of treatment, the patient's views if known, and the views of the people close to the patient. In Britain the decision to withdraw artificial nutrition from a patient in a persistent vegetative state requires consultation with the courts.

Consultant neurologist Reader in neurology National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG
Robin S Howard, David H Miller

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