A vegetative state occurs when the cerebrum (the part of the brain that controls thought and behavior) is functionally disabled, but the hypothalamus and brain stem (the parts of the brain that control vital functions, such as sleep cycles, body temperature, breathing, blood pressure, heart rate, and consciousness) continue to function. Thus, people open their eyes and appear awake at intervals of time over a 24-hour cycle but otherwise do not respond to stimulation in any meaningful way.
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 show spontaneous opening of the eyes, but they do not 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 sometimes called unresponsive wakefulness syndrome.
Traditionally, the term persistent vegetative state was used to describe unresponsive wakefulness that lasts for more than 1 month, but this term is no longer used and is replaced by the term chronic.
Most people in a chronic vegetative state for more than 2 years do not recover any mental function or ability to interact with the environment in a meaningful way. However, a few people improve enough that the diagnosis is changed to minimally conscious state after 2 years have elapsed. In people in a minimally conscious state, awareness is severely but not completely impaired. The person typically has good language comprehension, can follow simple commands, gesture to indicate "yes" or "no," and produce intelligible speech and other purposeful behaviors. Meaningful recovery from minimally conscious state has occurred after very long time intervals, including those greater than 10 years.
When any recovery occurs, the initial cause of brain damage was usually due to a head injury (traumatic brain injury), and not a disorder that resulted in the brain being deprived of oxygen. Also, recovery is often very limited. For example, people may only be able to reach for objects or utter the same word over and over. Rarely, slow recovery continues over months to years.
Causes of Vegetative State
A vegetative state occurs when the cerebrum (the higher centers of the brain including the cortex, thalamus, and related structures) is severely damaged, but the brain stem activating system is still functional (making a wakeful-appearing state possible). The brain stem activating system (also called 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
However, any disorder that severely damages the brain such as bleeding (hemorrhage) in the brain or a brain infection can result in a vegetative state.
Symptoms of Vegetative State
People in a vegetative state can do some things because some parts of the brain are functioning:
They spontaneously open their eyes.
They appear to have relatively regular sleeping and waking patterns (but not necessarily related to day and night and without normal electrical patterns).
They can breathe, suck, chew, cough, gag, swallow, and make guttural sounds.
They may be startled by loud noises and appear to smile or frown.
Because of these responses, they may appear to be aware of their surroundings. However, people in a vegetative state do not have behavioral awareness of themselves or their environment (otherwise, it is misdiagnosed). Their apparent responses to their surroundings result from automatic (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. They have no control over urination and bowel movements (are incontinent).
In approximately 1 in 4 people in a vegetative state, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) can detect evidence of higher-level brain activity, demonstrating preservation of both awareness and cognitive function. When such people were asked to imagine carrying out motor tasks on and off for approximately 5 minutes, EEG and MRI tests showed appropriate, sustained, and reproducible patterns of brain activity associated with such an action (although the people did not do the action). This is called cognitive motor dissociation (CMD). Prognosis for recovery is somewhat better when CMD is present.
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Diagnosis of Vegetative State
A doctor's evaluation
Tests such as magnetic resonance imaging and electroencephalography
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. The doctor may perform serial behavioral assessments, up to 5, using an approved assessment tool such as the Coma Recover Scale–Revised, to make an accurate diagnosis.
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 to determine evidence of awareness and preserved cognition. 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.
Treatment of Vegetative State
Preventive measures for problems due to immobilization
Good nutrition
Possibly, medications
Music therapy may have slight beneficial effects by stimulating a response in people in a vegetative state or other types of impaired consciousness. But the usefulness of this therapy is as yet unclear.
Some medications , such as amantadine (used to treat viral infections), zolpidem (a sleep aid), or apomorphine (used for Parkinson disease), may be tried to see if they can improve consciousness. Individual results are uncertain and no treatment has been proved consistently effective in the long term. Amantadine, however, has shown sufficient benefit in controlled clinical trials to warrant testing in all patients.
Long-term care
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. Medications 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 and shortening 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 medications 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.
Other issues
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).
Prognosis for Vegetative State
Some people spontaneously recover from a vegetative state, but recovery is usually incomplete. 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 an overdose of a medication or an illicit drug rather than a major stroke or cardiac arrest.
Younger people may recover more use of their muscles than older adults, but differences in recovery of mental function, behavior, and speech are not significant.
If a vegetative state lasts for more than a year, people are unlikely to recover consciousness. If people do recover, they are likely to be severely disabled.
However, a few people improve over a period of months or years. Some reports of people in an apparent vegetative state regaining full consciousness after years have, to date, all reflected people who actually had been in a minimally conscious state. Rarely, improvement occurs late in people appropriately diagnosed with vegetative state, and in these cases recovery is typically to the level of minimally conscious state or just emerged from that level. After 3 to 5 years, about 3 to 5% 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. A few people live for several years.
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