Most commonly, a vegetative state is caused by severe brain damage due to a head injury or a disorder that deprives the brain of oxygen, such as cardiac or respiratory arrest.
People in a vegetative state can open their eyes, but they cannot speak or do things that require thought or conscious intention, and they have no awareness of themselves or their environment.
Doctors diagnose a vegetative state only after they observe people for a period of time and on more than one occasion and do not find any evidence of awareness.
People in a vegetative state require comprehensive care, including good nutrition and measures to prevent problems that result from not being able to move (such as pressure sores).
The vegetative state is rare. Traditionally, a vegetative state has been considered a long-lasting (chronic) disorder. That is, if a person appears to be in a vegetative state at first but recovers some mental (cognitive) function in a few weeks, that person was never in a vegetative state.
A vegetative state that lasts for more than 1 month is considered a persistent vegetative state. Most people with a persistent vegetative state do not recover any mental function or ability to interact with the environment in a meaningful way. However, a few people with a persistent vegetative state improve enough that the diagnosis is changed to minimally conscious state. In people in a minimally conscious state, awareness is severely but not completely impaired. When any recovery occurs, the cause was usually brain damage due to a head injury (traumatic brain injury), not a disorder that resulted in the brain being deprived of oxygen. Also, recovery is often very limited. For example, people may reach for any and all objects or may utter the same word over and over. Rarely, people in a persistent vegetative state due to a head injury continue to slowly improve over months to years.
How many people are in a vegetative state is unknown, but about 25,000 adults and almost 10,000 children in the United States are thought to have this disorder.
A vegetative state occurs when the cerebrum (the largest part of the brain) is severely damaged (making mental function impossible), but the reticular activating system is still functional (making wakefulness possible). The reticular activating system controls whether a person is awake (wakefulness). It is a system of nerve cells and fibers located deep within the upper part of the brain stem (the part of the brain that connects the cerebrum with the spinal cord).
Most commonly, a vegetative state is caused by severe brain damage due to
A disorder that deprives the brain of oxygen, such as cardiac arrest or respiratory arrest
People in a vegetative state can do some things because some parts of the brain are functioning:
Because of these responses, they may appear to be aware of their surroundings. However, they have no awareness of themselves or their environment. Their apparent responses to their surroundings result from involuntary basic reflexes and not from a conscious action. For example, they may instinctively grasp an object when it touches their hand, as a baby does.
People in a vegetative state cannot do things that require thought or conscious intention. They cannot speak, follow commands, move their limbs purposefully, or move to avoid a painful stimulus.
Most people in a vegetative state have lost all capacity for awareness, thought, and conscious behavior. However in a few people, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) have detected evidence of some brain activity suggesting possible awareness. In these people, the cause was usually a head injury, not a disorder that resulted in the brain being deprived of oxygen. When the people were asked to imagine moving a part of their body, these tests showed appropriate brain activity for such an action (although the people did not do the action). However, these tests cannot determine how much awareness these people have. Awareness that can be detected only by these tests is called covert (hidden) consciousness.
People in a vegetative state have no control over urination and bowel movements (are incontinent).
Doctors suspect a vegetative state based on symptoms. However, before a vegetative state can be diagnosed, people should be observed for a period of time and on more than one occasion. If people are not observed long enough, evidence of awareness may be missed. People who have some awareness may be in a minimally conscious state rather than a vegetative state.
An imaging test, such as magnetic resonance imaging (MRI) or computed tomography (CT), is done to check for disorders that may be causing the problem, especially those that can be treated. If the diagnosis is in doubt, doctors may do other imaging tests—positron emission tomography (PET) or single-photon emission computed tomography (SPECT). These tests can indicate how well the brain is functioning.
Electroencephalography (EEG) may be done to check for abnormalities in the brain's electrical activity that suggest seizures, which may impair consciousness.
Functional MRI (fMRI) may be done to check for brain activity and thus determine whether awareness is completely impaired. This test can detect when a person responds to questions and commands, even when the response is not apparent—that is, when the person does not speak or move in response (covert consciousness). EEG can also detect this brain activity. The results of these tests can affect decisions about long-term care.
Some people spontaneously recover from a vegetative state. The chances of recovery depend on the cause and extent of the brain damage and the person's age, as for the following:
Some recovery is more likely if the cause is a head injury, a reversible metabolic abnormality (such as low blood sugar), or a drug overdose rather than a major stroke or cardiac arrest.
Younger people may recover more use of their muscles than older people, but differences in recovery of mental function, behavior, and speech are not significant.
If a vegetative state lasts for more than a few months, people are unlikely to recover consciousness. If people do recover, they are likely to be severely disabled.
Recovery from a vegetative state is unlikely after 1 month if the cause was anything other than a head injury. If the cause was a head injury, recovery is unlikely after 12 months. However, a few people improve over a period of months or years. Rarely, improvement occurs late. After 5 years, about 3% of people recover the ability to communicate and understand, but few can live independently, and none can function normally.
Most people who remain in a vegetative state die within 6 months of the original brain damage. Most of the others live about 2 to 5 years. The cause of death is often a respiratory or urinary tract infection or severe malfunction (failure) of several organs. But death may occur suddenly, and the cause may be unknown.
Like people in a coma, people in a vegetative state require comprehensive care.
Providing good nutrition (nutritional support) is important. People are fed through a tube inserted through the nose and into the stomach (called tube feeding). Sometimes they are fed through a tube inserted directly into the stomach or small intestine through an incision in the abdomen. Drugs may also be given through these tubes.
Many problems result from being unable to move (immobilization), and measures to prevent them are essential (see Problems Due to Bed Rest). For example, the following can happen:
Pressures sores: Lying in one position can cut off the blood supply to some areas of the body, causing skin to break down and pressure sores to form.
Contractures: Lack of movement can also lead to permanent stiffening of muscles (contractures) causing joints to become permanently bent.
Blood clots: Lack of movement makes blood clots more likely to form in leg veins—called deep vein thrombosis.
Pressure sores can be prevented by frequently repositioning the person and placing protective padding under parts of the body that are in contact with the bed, such as the heels, to protect them.
To prevent contractures, physical therapists gently move the person’s joints in all directions (passive range-of-motion exercises) or splint joints in certain positions.
Preventing blood clots includes use of drugs and compression or elevation of the person's legs. Moving the limbs, as occurs in passive-range-of-motion exercises, may also help prevent blood clots.
Because people are incontinent, care should be taken to keep the skin clean and dry. If the bladder is not functioning and urine is being retained, a tube (catheter) may be placed in the bladder to drain urine. Catheters are carefully cleaned and regularly examined to prevent urinary tract infections from developing.
If recovery is unlikely, doctors, family members, and sometimes the hospital ethics committee should discuss how aggressively future medical problems should be pursued and when and if life-sustaining treatment should be withdrawn. A person's wishes about such treatments should be considered if they are known—for example, if wishes have been stated in an advance directive (living will).