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A vegetative state occurs when the cerebrum (the part of the brain that controls thought and behavior) no longer functions, 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 but otherwise do not respond to stimulation in any meaningful way. They cannot speak and have no awareness of themselves or their environment.
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 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. People with a persistent vegetative state rarely recover any mental function or ability to interact with the environment in a meaningful way. 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. Even fewer people with a persistent vegetative state continue to slowly improve over months to years.
How many people are in a vegetative state is unknown, but about 25,000 people 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 head injury
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, these 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 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.
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).
Electroencephalography (EEG) may be done to check for abnormalities in the brain's electrical activity that suggest seizures, which may impair consciousness.
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 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.
The longer a vegetative state lasts, the more severe the disabilities are likely to be.
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 are in a vegetative state die within 6 months. 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. Sometimes they are fed through a tube (called a percutaneous endoscopic gastrostomy tube, or PEG tube) inserted directly into the stomach through an incision in the abdomen. Drugs may also be given through this tube.
Many problems result from being unable to move, 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. Caregivers must turn people very frequently.
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.
To prevent these problems, physical therapists gently move the person’s joints in all directions (passive range-of-motion exercises). Therapists may splint joints in certain positions to help prevent contractures. People are also given drugs to prevent blood clots from developing.
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.
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).
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