Stupor is unresponsiveness from which a person can be aroused only by vigorous, physical stimulation. Coma is unresponsiveness from which a person cannot be aroused. In coma, the person's eyes remain closed.

• The cause is usually a disorder or drug that affects large areas on both sides of the brain or specialized areas of the brain involved in maintaining consciousness.
• A physical examination, blood tests, brain imaging, and information from family and friends help doctors identify the cause.
• Possible causes are corrected, and treatments to support body functions, such as a ventilator, are provided.
• Recovery from a coma depends largely on the cause.

Normally, the brain can quickly adjust its own levels of activity and consciousness as needed. The brain makes these adjustments based on information it receives from the eyes, ears, skin, and other sensory organs. For example, the brain can decrease its metabolic activity and induce sleep.

Consciousness is controlled by the lower part of the brain (brain stem) through a system of nerve cells and fibers (the reticular activating system, also known as the ascending arousal system (see Biology of the Nervous System: Brain Stem). The upper part of the brain (cerebrum) helps maintain consciousness and alertness. The cerebrum is divided into two halves (cerebral hemispheres). At least one hemisphere, as well as the reticular activating system, must be functioning normally to maintain consciousness.

The brain's ability to adjust its activity and consciousness levels can be impaired in several ways:

• When people are severely deprived of sleep
• When and immediately after a seizure occurs
• When both cerebral hemispheres are suddenly and severely damaged
• When the reticular activating system malfunctions
• When blood flow or the amount of nutrients (such as oxygen or sugar) going to the brain decrease
• When toxic substances impair the brain

Periods of impaired consciousness can be short or long. The level of impairment can range from slight to severe:

• Lethargy is a slight reduction in alertness or clouding of consciousness. People tend to be less aware of what is happening around them and to think more slowly.
• Obtundation, an imprecise term, refers to a moderate reduction in alertness or clouding of consciousness.
• Stupor is an excessively long or deep sleeplike state. A person can be aroused from it only briefly by vigorous stimulation, such as repeated shaking, loud calling, pinching, or sticking with a pin.
• Coma is a state of complete unresponsiveness. A person cannot be aroused at all. A person in a deep coma lacks even the most basic responses, such as avoidance of pain, although reflexes may be present.

Causes

The various levels of impaired consciousness—lethargy, obtundation, stupor, and coma—have the same causes, of which there are many. Most commonly, the cause is a toxic substance, drug, metabolic abnormality, or another disorder that makes nerve cells throughout the brain function slowly. Some of these causes interfere with the delivery of needed substances to the brain or the body's ability to use them. Examples are a very low or high level of sugar in the blood (hypoglycemia or hyperglycemia), a very low level of oxygen in the blood, and the sudden stopping of the heart's pumping (cardiac arrest).

Spotlight on Aging
Stupor and coma are particular concerns among older people for the following reasons: Drugs and relatively minor disorders are more likely to impair consciousness in older people, sometimes leading to stupor and coma. Drugs are a common cause of impaired consciousness, often because too much is taken. Older people may take too much when doctors prescribe a dose that is too high. Older people are more sensitive to many drugs, and a lower dose is often needed. Sometimes older people take too much of a drug by mistake. Also, older people take more drugs, increasing the risk of drug interactions. A urinary tract infection or dehydration usually has no serious effects in young adults but often impairs consciousness in older adults. Many disorders that are more common among older people can cause stupor or coma. They include strokes, brain tumors, bulges in weakened arteries (aneurysms) in the brain, metabolic disorders, and severe heart or lung disorders. If older people become less alert or less conscious of things around them, family members and friends may not notice or may assume that the change results from aging. A change in consciousness may be harder to discern in older people who have dementia or another brain disorder or who have had a stroke. Older people are less likely to recover from stupor or coma because the brain becomes less able to repair itself as people age.

Disorders such as liver or kidney failure, an underactive thyroid gland (hypothyroidism), or a very low or high body temperature (hypothermia or hyperthermia) can cause many types of cells throughout the body to malfunction. Often, brain cells are affected the most.

Commonly, consciousness is impaired by drinking too much alcohol or taking too much of certain drugs, such as sedatives (see Sleep Disorders: Prescription Sleep Aids: Not to Be Taken Lightly) and opioids (narcotics—see Opioid Analgesics). In addition to making brain cells function slowly, alcohol and some drugs can damage brain cells indirectly. They can slow breathing so much that the oxygen level in blood becomes low enough to cause brain damage. Occasionally, taking certain antipsychotic drugs results in an unresponsive state called neuroleptic malignant syndrome (see Schizophrenia and Delusional Disorder: What Is Neuroleptic Malignant Syndrome?).

In older people, reactions to drugs, dehydration (which results in a high sodium level), and infections are common causes of impaired consciousness.

Other common causes are disorders that affect the areas of the brain that control consciousness. For example, a head injury may jar but not physically damage (stun) such areas, directly damage them, or indirectly damage them by causing bleeding (hemorrhage) in or around the brain. Strokes and tumors can also directly damage areas of the brain that control consciousness.

A mass in the brain, such as an accumulation of blood (hematoma), a tumor, or an abscess, can impair consciousness indirectly. A large mass can push the brain against the relatively rigid structures inside the skull, damaging brain tissue. If the areas of the brain that control consciousness are affected, stupor or coma results. The pressure may affect the entire cerebrum or the brain stem. If the pressure is high enough, the brain may be forced through a small natural opening in the relatively rigid sheets of tissue that separate the brain into compartments. This life-threatening disorder is called brain herniation (see Head Injuries:Overview of Head Injuries). Herniation can further damage brain tissue, making an already dire condition worse.

PrintOpen table in new window
Some Causes of Stupor and Coma What? How? What Happens? Brain disorders Seizures Seizures that recur frequently or last a long time, can Overstimulate brain tissue, disrupting normal transmission of nerve impulses Cause a high fever, which may make the brain malfunction or damage brain tissue Some people remain unresponsive for hours after a seizure. Consciousness can be impaired. Strokes Strokes can block blood flow to parts of the brain, including to the brain stem. If blood flow to the brain stem is blocked, consciousness may be suddenly lost, and coma can result. If blood flow to the entire brain stem is blocked and not restored within a few minutes, most or all of the brain stem is damaged, and death may result. Strokes may result from bleeding in the brain (intracerebral hemorrhage) or around it (subarachnoid hemorrhage). Blood can directly irritate brain tissue or increase pressure on it. Blood can directly damage or increase pressure on brain tissue. Consciousness may be impaired, and coma may result. Even a small amount of bleeding in the brain stem can cause coma. Tumor or abscess A large tumor or abscess can push the brain against the relatively rigid structures inside the skull and put pressure on brain tissue, causing it to malfunction. Tumors can directly invade and damage brain tissue. If the areas of the brain that control consciousness are affected, coma results. Other disorders Cardiac arrest In cardiac arrest, the heart stops pumping. Consequently, the brain does not receive enough blood, which carries oxygen to tissues. Brain tissue dies because it is deprived of oxygen. Consciousness is lost within a minute or two. Nerve cells may die if cardiac arrest lasts even 4 to 5 minutes. Coma results and may soon become irreversible. Heart or lung disorders if severe Severe heart disorders (such as heart failure) can reduce blood flow to the brain. Severe lung disorders (such as chronic obstructive pulmonary disease, pulmonary edema, pulmonary embolism, and severe and long-lasting asthma attacks) can reduce the amount of oxygen in the blood. With either type of disorder, the brain may not receive enough oxygen, sometimes resulting in coma. Kidney failure Liver encephalopathy or failure If the kidneys or liver cannot remove toxic waste products from the blood as they normally do, waste products accumulate in the blood and cause the brain to malfunction. If coma results from chronic kidney or liver failure, it is usually reversible. If coma results from acute, severe liver failure, the brain swells because fluid accumulates in brain cells. Death often results. Metabolic abnormalities Hyperglycemia The blood sugar level is abnormally high. The blood becomes syrupy, drawing fluid from the brain. Stupor or coma can result. Hypoglycemia The blood sugar level is abnormally low. The brain malfunctions or is damaged if it is deprived of sugar, which is its main source of energy. Coma can result. Immediate treatment with glucose, given intravenously soon after coma develops, prevents permanent brain damage. Hypernatremia The blood sodium level is high. Hypernatremia is usually due to dehydration and can reduce the amount of water in brain cells. An abnormal amount of water in brain cells interferes with chemical reactions there. Stupor or coma may result. Hyponatremia The blood sodium level is low. Hyponatremia may be due to the following: Drinking too much water (for example, during college fraternity rituals) Retaining too much water Losing too much sodium in urine or in the digestive tract (as when diarrhea occurs) This disorder can increase the amount of water in brain cells. An abnormal amount of water in brain cells interferes with chemical reactions there. Stupor, coma, and seizures may result. Hypothyroidism The thyroid gland is underactive. Untreated hypothyroidism may cause mental confusion and slowed thinking. The confusion may progress to stupor and coma. Infections If brain tissue becomes infected, the brain may malfunction. Causes include infection of the brain (encephalitis) and infection of the membranes lining the brain and spinal cord (meningitis). Other infections, such as sepsis, can cause high fevers, which may make the brain malfunction or damage brain tissue. Coma may result. Accidents and injuries Asphyxiation The brain is deprived of oxygen. Consciousness is quickly lost, and coma and death may follow. Head injury Head injuries may damage the brain in the following ways: Jar the brain without physically damaging it (as in a concussion) Bruise the brain (as in a contusion) Cut or crush brain tissue Cause bleeding in or around the brain (as in an intracerebral or a subarachnoid hemorrhage) Blood may directly irritate brain tissue or may accumulate as a mass (hematoma), which puts pressure on the brain (as in epidural or subdural hematoma). Depending on the injury, coma may develop immediately or gradually over several hours. Hyperthermia A body temperature above 104° F (40° C), as occurs in high fevers or heatstroke, can damage the brain. Coma can result. Nerve cells die much more quickly when body temperature is very high. Hypothermia A body temperature below 88° F (31.1° C) slows brain function. However, low temperatures can actually protect the brain by slowing the damage caused by lack of blood or oxygen. Also, nerve cells die much more slowly when body temperature is very low. For example, a child may fully recover after being submersed for 30 minutes in an icy lake. Being submersed that long in warm water is usually fatal. Stupor or coma can result but usually without permanent damage if people survive. Some people recover completely. Substances Alcohol Alcohol slows brain function. Consumed in large amounts, it may affect brain tissue directly or indirectly by slowing breathing so much that the oxygen level in blood becomes low enough to cause brain damage. A high blood alcohol level, especially when it exceeds 0.2%, can cause stupor or coma. Carbon monoxide or similar substances inhaled in large amounts Carbon monoxide attaches to the hemoglobin in red blood cells. It takes the place of oxygen and prevents red blood cells from carrying oxygen to tissues, including the brain. Severe carbon monoxide poisoning can cause coma or irreversible brain damage because the brain does not receive enough oxygen. Drugs Many drugs even if not given in high doses can affect brain function. For example, high doses of barbiturates, opioids (including morphine), a sedative (such as diazepam), or these drugs combined with each other or with alcohol can slow brain function. A coma can result. If treated early, this type of coma can be completely reversed. Some Causes of Stupor and Coma What? How? What Happens? Brain disorders Seizures Seizures that recur frequently or last a long time, can Overstimulate brain tissue, disrupting normal transmission of nerve impulses Cause a high fever, which may make the brain malfunction or damage brain tissue Some people remain unresponsive for hours after a seizure. Consciousness can be impaired. Strokes Strokes can block blood flow to parts of the brain, including to the brain stem. If blood flow to the brain stem is blocked, consciousness may be suddenly lost, and coma can result. If blood flow to the entire brain stem is blocked and not restored within a few minutes, most or all of the brain stem is damaged, and death may result. Strokes may result from bleeding in the brain (intracerebral hemorrhage) or around it (subarachnoid hemorrhage). Blood can directly irritate brain tissue or increase pressure on it. Blood can directly damage or increase pressure on brain tissue. Consciousness may be impaired, and coma may result. Even a small amount of bleeding in the brain stem can cause coma. Tumor or abscess A large tumor or abscess can push the brain against the relatively rigid structures inside the skull and put pressure on brain tissue, causing it to malfunction. Tumors can directly invade and damage brain tissue. If the areas of the brain that control consciousness are affected, coma results. Other disorders Cardiac arrest In cardiac arrest, the heart stops pumping. Consequently, the brain does not receive enough blood, which carries oxygen to tissues. Brain tissue dies because it is deprived of oxygen. Consciousness is lost within a minute or two. Nerve cells may die if cardiac arrest lasts even 4 to 5 minutes. Coma results and may soon become irreversible. Heart or lung disorders if severe Severe heart disorders (such as heart failure) can reduce blood flow to the brain. Severe lung disorders (such as chronic obstructive pulmonary disease, pulmonary edema, pulmonary embolism, and severe and long-lasting asthma attacks) can reduce the amount of oxygen in the blood. With either type of disorder, the brain may not receive enough oxygen, sometimes resulting in coma. Kidney failure Liver encephalopathy or failure If the kidneys or liver cannot remove toxic waste products from the blood as they normally do, waste products accumulate in the blood and cause the brain to malfunction. If coma results from chronic kidney or liver failure, it is usually reversible. If coma results from acute, severe liver failure, the brain swells because fluid accumulates in brain cells. Death often results. Metabolic abnormalities Hyperglycemia The blood sugar level is abnormally high. The blood becomes syrupy, drawing fluid from the brain. Stupor or coma can result. Hypoglycemia The blood sugar level is abnormally low. The brain malfunctions or is damaged if it is deprived of sugar, which is its main source of energy. Coma can result. Immediate treatment with glucose, given intravenously soon after coma develops, prevents permanent brain damage. Hypernatremia The blood sodium level is high. Hypernatremia is usually due to dehydration and can reduce the amount of water in brain cells. An abnormal amount of water in brain cells interferes with chemical reactions there. Stupor or coma may result. Hyponatremia The blood sodium level is low. Hyponatremia may be due to the following: Drinking too much water (for example, during college fraternity rituals) Retaining too much water Losing too much sodium in urine or in the digestive tract (as when diarrhea occurs) This disorder can increase the amount of water in brain cells. An abnormal amount of water in brain cells interferes with chemical reactions there. Stupor, coma, and seizures may result. Hypothyroidism The thyroid gland is underactive. Untreated hypothyroidism may cause mental confusion and slowed thinking. The confusion may progress to stupor and coma. Infections If brain tissue becomes infected, the brain may malfunction. Causes include infection of the brain (encephalitis) and infection of the membranes lining the brain and spinal cord (meningitis). Other infections, such as sepsis, can cause high fevers, which may make the brain malfunction or damage brain tissue. Coma may result. Accidents and injuries Asphyxiation The brain is deprived of oxygen. Consciousness is quickly lost, and coma and death may follow. Head injury Head injuries may damage the brain in the following ways: Jar the brain without physically damaging it (as in a concussion) Bruise the brain (as in a contusion) Cut or crush brain tissue Cause bleeding in or around the brain (as in an intracerebral or a subarachnoid hemorrhage) Blood may directly irritate brain tissue or may accumulate as a mass (hematoma), which puts pressure on the brain (as in epidural or subdural hematoma). Depending on the injury, coma may develop immediately or gradually over several hours. Hyperthermia A body temperature above 104° F (40° C), as occurs in high fevers or heatstroke, can damage the brain. Coma can result. Nerve cells die much more quickly when body temperature is very high. Hypothermia A body temperature below 88° F (31.1° C) slows brain function. However, low temperatures can actually protect the brain by slowing the damage caused by lack of blood or oxygen. Also, nerve cells die much more slowly when body temperature is very low. For example, a child may fully recover after being submersed for 30 minutes in an icy lake. Being submersed that long in warm water is usually fatal. Stupor or coma can result but usually without permanent damage if people survive. Some people recover completely. Substances Alcohol Alcohol slows brain function. Consumed in large amounts, it may affect brain tissue directly or indirectly by slowing breathing so much that the oxygen level in blood becomes low enough to cause brain damage. A high blood alcohol level, especially when it exceeds 0.2%, can cause stupor or coma. Carbon monoxide or similar substances inhaled in large amounts Carbon monoxide attaches to the hemoglobin in red blood cells. It takes the place of oxygen and prevents red blood cells from carrying oxygen to tissues, including the brain. Severe carbon monoxide poisoning can cause coma or irreversible brain damage because the brain does not receive enough oxygen. Drugs Many drugs even if not given in high doses can affect brain function. For example, high doses of barbiturates, opioids (including morphine), a sedative (such as diazepam), or these drugs combined with each other or with alcohol can slow brain function. A coma can result. If treated early, this type of coma can be completely reversed.

Symptoms

The brain damage or dysfunction that causes stupor and coma affects other parts of the body. The pattern of breathing is usually abnormal. People may breathe too rapidly, too slowly, too deeply, or irregularly. Or they may alternate between these abnormal patterns.

Muscles may remain contracted in unusual positions. For example, the head may be tilted back with the arms and legs extended—a position called decerebrate rigidity. The arms may be flexed—a position called decorticate rigidity. Or the entire body may be limp. Sometimes muscles contract sporadically or involuntarily.

One or both pupils of the eyes may be widened (dilated) and not react to changes in light. Or the pupils may be tiny. The eyes may not move or may move in abnormal ways.

Diagnosis

Doctors can usually tell that consciousness is impaired based on observation and examination. Doctors try to identify the level and cause of impairment because treatment differs and because impairment may progress, leading to coma and brain death. Stupor is diagnosed when vigorous, repeated attempts arouse the person only briefly. Coma is diagnosed when the person cannot be aroused at all.

People who become stuporous or comatose must be taken to the hospital immediately because either state may be caused by a life-threatening disorder. Health care practitioners try to identify the cause and provide emergency medical care at the same time.

People with disorders that put them at risk of stupor or coma (such as diabetes, which can result in a low blood sugar level) should carry medical identification or wear a Medic Alert identification bracelet or necklace. Thus, if they lose consciousness, the probable cause can be quickly identified.

Because a stuporous or comatose person cannot communicate, family members and friends must honestly provide emergency medical personnel or the doctor with any relevant information about the person, which includes the following:

• Whether the person uses drugs (prescription and recreational), alcohol, or other toxic substances and which ones are used
• Whether the person was injured before the change in consciousness
• When and how the problem began
• Whether the person has had any infections or other symptoms (such as headaches or vomiting)
• When the person last seemed normal

If a drug or toxic substance was ingested, family members or friends should give a sample of that substance or its container to the doctor. Information from the family and friends usually is valuable and is more likely to lead to the correct diagnosis than examination or testing. For example, no test can rule out all possible drug overdoses. Thus, information about empty pill containers or drug paraphernalia near the person is extremely important.

Physical Examination: Emergency medical personnel or doctors first check whether the airway is open, whether breathing is adequate, and whether blood pressure and pulse are normal. Body temperature is checked. For example, an abnormally high temperature may indicate infection, heatstroke, or an overdose of a drug that stimulates the body (such as cocaine or an amphetamine). An abnormally low temperature may indicate prolonged exposure to cold, an underactive thyroid gland, alcohol intoxication, a sedative overdose or, in older people, infection. The skin is examined for signs of injury, drug injections, illnesses, and allergic reactions, and the scalp is examined for cuts and bruises. The tongue is examined to see if it has been bitten—a finding that suggests seizures.

A neurologic examination is done as thoroughly as possible. This examination helps doctors determine how severe stupor or coma is, whether the brain stem is functioning normally, and what part of the central nervous system is damaged.

Doctors may use stimuli that cause discomfort or trigger reflexes. If the eyes open or the person grimaces or purposefully withdraws from a painful stimulus, consciousness is not severely impaired.

Doctors look for signs of brain damage or impaired brain function. For example, abnormal breathing patterns can provide clues to the depth of coma. Checking reflexes can help determine whether parts of the brain and spinal cord are malfunctioning. Unusual body positions, such as decerebrate or decorticate rigidity, may indicate substantial brain damage. Absence of reflexes and limpness of the entire body are worrisome. They may indicate widespread dysfunction in all parts of the central nervous system, including the brain stem, the cerebrum, and the nerve fibers that connect the cerebrum to the spinal cord.

The eyes also provide important clues. The position of the pupils, their size, their reaction to bright light, their ability to follow a moving object (in people who are not comatose), and the appearance of the retina are checked. If a pupil remains dilated and does not react to bright light, there may be pressure on the 3rd cranial nerve, which helps control eye movement, or on the brain stem. Such a reaction sometimes indicates a large mass in the brain causing herniation. If coma is deep and both pupils do not remain dilated but react to light, this type of a mass is unlikely. To accurately evaluate the person, doctors need to know whether the person's pupils are normally different sizes, and whether the person takes a drug to treat glaucoma, which can affect pupil size.

The person's response to certain maneuvers can provide additional information:

• Rotating the head and observing eye movements can help doctors determine whether the brain stem is functioning normally.
• Squirting cold water into one or both ears and observing eye movements can determine whether the person is really unresponsive and, if so, whether the brain stem is damaged.

Laboratory Tests: These tests provide further clues about the possible cause of stupor or coma. Blood levels of substances such as sugar, sodium, alcohol, oxygen, and carbon dioxide are measured. The red and white blood cell counts are determined. Blood tests to check liver function are done. Urine is analyzed to determine whether any commonly used or suspected toxic substances are present. The blood sugar level is also estimated using a quick test done at the person's bedside, so that a low blood sugar level can be treated immediately.

Other Tests: If no cause has been quickly identified, computed tomography (CT) or magnetic resonance imaging (MRI) of the head is done to check for a mass (such as a hematoma, a tumor, or an abscess), or for other structural brain damage.

If the cause is unclear after imaging tests or if meningitis or subarachnoid hemorrhage is possible, a spinal tap (lumbar puncture) is done to withdraw and examine a sample of cerebrospinal fluid (see Symptoms and Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Tests for Brain, Spinal Cord, and Nerve Disorders). Emergency CT or MRI of the head is often done before the spinal tap to determine whether pressure inside the skull is increased (for example, by a tumor or hemorrhage). If pressure is increased, a spinal tap could make the brain shift downward by rapidly reducing the pressure below the brain and thus, at least theoretically, cause or worsen brain herniation.

If the cause is still unclear, electroencephalography (EEG) is done to check the brain's electrical activity. Occasionally, EEG indicates that the person is having a seizure even though the limbs are not jerking (a disorder called nonconvulsive status epilepticus).

Did You Know... People in a locked-in state can think normally but appear unresponsive because they cannot move any part of their body except their eyes. People in a vegetative state go to sleep and awaken normally and have eye movements but have actually lost all capacity for thought and conscious behavior.

Treatment

A rapidly deteriorating level of consciousness is a medical emergency requiring immediate treatment, sometimes even before a diagnosis is made.

People are admitted to a hospital intensive care unit, where nurses can monitor heart rate, blood pressure, temperature, and the oxygen level in the blood. Any abnormalities in these levels are immediately corrected to prevent further damage to the brain. Oxygen is often given immediately, and an intravenous line is put in place so that drugs can be given quickly. Any other disorders (such as heart or lung disorders) present are treated.

The cause is treated when possible. For example, for a low blood sugar level (hypoglycemia), glucose, a sugar, is immediately given intravenously. Giving glucose often results in instant recovery if the coma is caused by hypoglycemia. Thiamin is always given with glucose because in malnourished people (such as alcoholics), glucose alone can trigger or worsen a brain disorder called Wernicke's encephalopathy. If taking an opioid is the suspected cause, the antidote naloxone may be given. Recovery may be almost instantaneous if the opioid is the only cause of impaired consciousness.

People with deep stupor or in a coma may require a breathing tube, particularly if a feeding tube is to be inserted into the stomach. The breathing tube prevents people from inhaling stomach contents after vomiting and facilitates mechanical ventilation if their breathing is too slow or shallow. Rarely, when doctors suspect that certain toxic substances have been ingested within about 1 hour, a large tube may be inserted into the stomach so that the stomach can be pumped. Pumping the stomach is done to identify its contents and to prevent more of the substances from being absorbed. Activated charcoal may also be given through the tube or through a smaller tube inserted through the nose (nasogastric tube) to prevent further absorption of the substances.

If findings suggest that the pressure inside the skull is increased, doctors may drill a small hole in the skull and insert a pressure monitoring device into one of the fluid-filled spaces (ventricles) in the brain. If the pressure is increased, measures are taken to lower it:

• The head of the bed may be elevated.
• Diuretics or other drugs may be used to reduce fluids in the brain and rest of the body.
• A sedative may be given to control excess involuntary muscular contractions, which can increase pressure within the skull.
• Blood pressure is sometimes lowered.
• Occasionally, the skull is opened surgically, creating more room for the swollen brain and thus reducing pressure on the brain.

Long-Term Care: People in a coma require comprehensive care. They are fed through a tube inserted through the nose and into the stomach. Sometimes a tube (called a percutaneous endoscopic gastrostomy tube or PEG tube) is inserted through an incision in the abdomen directly into the stomach.

Many problems result from being unable to move, and measures to prevent them are essential. For example, 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. Caretakers must turn people into different positions very frequently. Lack of movement can also lead to permanent stiffening of muscles (contractures) and make 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) and may splint joints in certain positions that tend to prevent contractures. Because people cannot blink, their eyes may become dry. Eye drops can help.

People who are incontinent should be kept clean from urine and stool. If the person's bladder is not functioning and urine is being retained, then doctors prefer using intermittent urinary catheterization over placing an indwelling catheter to reduce the risk of infection.

Prognosis

The likelihood of recovery can be predicted by the cause, duration, and rate of recovery from coma:

• Overdose of a sedative: Recovery is likely unless people stopped breathing long enough to cause brain damage.
• A low blood sugar level: Complete recovery is possible if the brain was not deprived of sugar for more than about 1 hour.
• Head injury: Substantial recovery may occur, even if the coma lasts several weeks (but not if it lasts more than 3 months).
• Stroke: Permanent brain damage is likely if coma lasts 6 hours or longer.
• Cardiac arrest or oxygen deprivation: Full recovery rarely occurs in the following cases. After 1 day, the pupils do not quickly begin to narrow (constrict) in response to light. After 3 days, people do not blink reflexively when the cornea is touched and do not move their limbs purposefully. After 1 week, people cannot move the limbs when asked to do so.

Sometimes doctors use evoked responses to determine whether the brain stem is functioning. This test can accurately predict a poor prognosis after only 24 hours. The brain stem is stimulated, and EEG is used to detect the response.

Results of a physical examination can also help predict prognosis. Recovery is likely if one or more of the following occur within the first days:

• Speech returns, even if it is incomprehensible.
• The eyes can follow an object.
• People can follow commands.

Children and sometimes young adults recover more fully than older people because brain cells repair themselves more quickly and completely in the young.

For people who remain in a deep coma longer than a few weeks, decisions about continued use of a ventilator, feeding tube, and drugs should be made. Family members should discuss these issues with the doctors. If people have advance medical directives (see Legal and Ethical Issues: Advance Directives), such as a living will or durable power of attorney for health care, the directives should guide decisions about continuing care.

Variations in Impaired Consciousness
Vegetative state: This state results when the cerebrum, which controls thought and behavior, can no longer function, but the thalamus and brain stem, which control sleep cycles, body temperature, breathing, blood pressure, and heart rate, can function. A vegetative state occasionally develops after severe brain damage due to a head injury, oxygen deprivation, or a severe brain infection such as meningitis or encephalitis. People in this state spontaneously open their eyes and have relatively normal sleeping and waking patterns. People can breathe, suck, chew, cough, gag, and swallow. They may even become startled in reaction to loud noises. So they may appear to be aware. However, they have lost all capacity for awareness, thought, and conscious behavior. Their apparent response to the environment is the result of reflexes. Most people in a vegetative state have obvious abnormal reflexes, including stiffening or jerking of the arms and legs. If a vegetative state lasts for more than a few months, people are unlikely to recover consciousness. Most people who recover consciousness after a few months are severely disabled. Minimally conscious state: In this state, people do a few things that indicate some awareness. They may reach for objects, answer “yes” whether it is appropriate or not, or follow objects with their eyes. This state may result directly from brain damage, or it may follow a vegetative state as people recover some function. A few people recover the ability to communicate and comprehend, sometimes after many years, but none recover the ability to function normally or live independently. Stimulation of deep parts of the brain and zolpidem (a sleep aid) are being studied as possible treatments. With skilled nursing care, these people can live for years. Locked-in state: People with this rare condition are conscious and able to think but are so severely paralyzed that they can communicate only by opening and closing the eyes in response to questions. The locked-in state can be caused by strokes that affect the brain stem but not the cerebrum, or by severe paralysis of peripheral nerves, as may result from severe Guillain-Barré syndrome. People in this state cannot move their lower face, chew, swallow, speak, breathe, move their limbs, or move their eyes from side to side. Sometimes they are mistakenly thought to be unconscious. Affected people are often very depressed. Speech therapists can help develop a communication code using eye blinks. If communication can be established, affected people should make their own health care decisions. Occasionally, when the cause can be corrected, people recover certain functions. Brain death: This condition is the most severe form of unconsciousness. The brain has permanently lost the ability to perform all vital functions, including breathing. The concept of brain death evolved partly because, with modern medicine, artificial means (such as ventilators and drugs) can maintain breathing and the heart's beating even when all brain activity stops. A brain-dead person is considered legally dead. There are specific criteria for diagnosing brain death: The person does not grimace, move, or otherwise react in response to any type of stimulation. The eyes do not react to light. The person makes no attempt to breathe. Also, doctors cannot diagnose brain death until they have corrected all treatable medical problems that could slow brain function and thus could be misdiagnosed as brain death. These problems include a very low body temperature, severe abnormalities in levels of substances (such as sugar and sodium) in the blood, overdose of a sedative, and ingestion of certain potentially toxic drugs. After these medical problems are corrected, brain death can be diagnosed. If the diagnosis is not clear, diagnostic procedures may be done to confirm brain death. Electroencephalography (EEG—a recording of the brain's electrical activity—see Symptoms and Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electroencephalography) shows no brain waves if a person is brain dead. Procedures may be done to show that blood is not flowing to the brain. They include angiography, single photon emission computed tomography (SPECT—which uses a radioactive molecule called a radionuclide to produce images of blood flow), and transcranial Doppler ultrasonography. Such procedures enable doctors to rapidly confirm brain death after catastrophic head injuries (as may occur in motor vehicle accidents). Also, when confirmation is quick, organ donation is possible. After brain death is confirmed, all life support is stopped. Family members may wish to be with the person at this time. They need to be told that the limbs may move when breathing assistance is ended. These movements result from reflex muscle contractions and do not mean the person is not really brain dead.

Last full review/revision February 2008 by Kenneth Maiese, MD