Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 84. Stupor and Coma

Topic: Stupor and Coma

Stupor and Coma

Stupor is an unresponsive state from which a person can be aroused only briefly and with vigorous, repeated attempts. Coma is an unresponsive state from which a person cannot be aroused, even with vigorous, repeated attempts.

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. The system of nerve cells and fibers that controls consciousness or arousal levels (the reticular activating system) is located deep within the brain stem (see Section 6, Chapter 76).

The brain's ability to adjust its activity and consciousness levels can be impaired. Impairment may result when the nerve fibers connecting the brain and the sensory organs malfunction, when blood flow to the brain decreases, or when toxic substances damage the brain.

Periods of impaired consciousness can be short or long. Levels of impaired consciousness can range from reduced alertness or clouded consciousness (obtundation) to stupor to coma. Stupor (hypersomnia) is an excessively long or deep sleeplike state from which a person can be awakened only briefly by vigorous stimulation, such as repeated shaking, loud calling, pinching, or sticking with a pin. Coma is a state of complete unresponsiveness, from which 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

Stupor or coma can be caused by many disorders. A head injury can directly damage the areas of the brain stem that control consciousness levels or can cause bleeding (hemorrhage) in or around the brain. Blood can also directly damage these areas of the brain stem, or an accumulation of blood (hematoma) can put pressure on these areas. Brain tumors or collections of pus (abscesses) can also put pressure on these areas.

Alcohol intoxication and overdose of certain drugs (such as sedatives (see Section 6, Chapter 81)--and opioids (see Section 6, Chapter 78)) are common causes of stupor or coma. Occasionally, the use of certain antipsychotic drugs results in an unresponsive state called neuroleptic malignant syndrome. Abnormally low or high levels of substances (including sugar and electrolytes such as sodium) in the blood can interfere with brain function and impair consciousness. Brain infections (such as encephalitis and meningitis) and severe infections outside the brain can lead to coma. In older people, toxic reactions to drugs, dehydration (which results in a high sodium level), and infections are common causes of stupor.

Other causes of stupor or coma include the sudden stopping of the heart's pumping (cardiac arrest), aneurysms, severe lung disorders, inhalation of carbon monoxide, stroke, seizures, an underactive thyroid gland (hypothyroidism), liver or kidney failure, and low or high body temperature (hypothermia or hyperthermia).

See the table Some Causes of Stupor and Coma.

Diagnosis

A person who becomes stuporous or comatose must be taken to the hospital immediately because either state may be caused by a life-threatening disorder. People with disorders that put them at risk of stupor or coma should carry medical identification or wear a Medic Alert identification bracelet or necklace. Thus, if they lose consciousness, medical personnel can quickly identify the probable cause.

Because a stuporous or comatose person cannot communicate, family members and friends must be honest with doctors about the person's use of drugs, alcohol, or other toxic substances. 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.

When emergency medical personnel or doctors examine a stuporous or comatose person, they first check whether the airway is open, whether breathing is adequate, and whether blood pressure and pulse are normal. Body temperature is checked: An abnormally high temperature may indicate infection; an abnormally low temperature may indicate prolonged exposure to cold, an underactive thyroid gland, alcohol intoxication, or, in older people, infection. The skin is examined for signs of injury, drug injections, and allergic reactions, and the scalp is examined for cuts and bruises. Doctors also perform as thorough a neurologic examination as is possible with a stuporous or comatose person.

Doctors look for signs of brain damage or impaired brain function. One sign of brain damage is Cheyne-Stokes respiration (periodic breathing), an unusual pattern in which a person breathes rapidly, then more slowly, then not at all for several seconds. Unusual postures may be signs of significant brain damage. Such postures include decerebrate rigidity, in which the head is tilted back and the arms and legs are extended, and decorticate rigidity, in which the arms are flexed. General limpness of the entire body is of even greater concern, indicating widespread loss of activity in all parts of the central nervous system, including the brain stem and the nerve fibers that connect the upper part of the brain (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. A widened (dilated) pupil that does not react to bright light may indicate pressure on cranial nerve III, which helps control eye movement, or on the brain stem. Doctors need to know if the person's pupils are normally different sizes or if the person takes a drug to treat glaucoma, which can affect pupil size.

Laboratory procedures 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. Urine is analyzed to determine whether sugar or toxic substances are present.

Additional procedures include computed tomography (CT) or magnetic resonance imaging (MRI) of the head to rule out the possibility of structural brain damage, such as that due to bleeding (hemorrhage), a tumor, or an abscess. If meningitis is remotely possible, a spinal tap (lumbar puncture) is performed to withdraw and examine a sample of cerebrospinal fluid (see Section 6, Chapter 77). Because a coma may also be due to a brain tumor or hemorrhage, emergency CT or MRI of the brain is often performed before the spinal tap to determine whether the increased pressure inside the skull has forced the brain downward in the skull. If the pressure is high enough, the brain may be forced through the 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 Section 6, Chapter 87). Performing a spinal tap reduces the pressure below the brain and thus may trigger or worsen a herniation.

Treatment

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

The person is admitted to a hospital intensive care unit, where nurses can monitor heart rate, blood pressure, temperature, and the oxygen level in the blood. Oxygen is often given immediately, and an intravenous line is put in place so that drugs can be given quickly. If the person is bleeding, attempts are made to stop the bleeding, and if blood loss is significant, a blood transfusion is given. Antiarrhythmic drugs (see Section 3, Chapter 27) may be given to keep the heart beating normally. If blood pressure continues to fall, fluids and drugs that narrow (constrict) blood vessels are given to keep blood pressure normal.

Usually, glucose, a sugar, is given intravenously after blood has been drawn to measure the blood sugar level but before the blood sugar level has been determined. Giving glucose often results in instant recovery if the cause of the coma is a low blood sugar level (hypoglycemia). Thiamine 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 (narcotic) is the suspected cause, the antidote naloxone may be given while doctors wait for blood and urine test results. If ingestion of a toxic substance is suspected, the stomach may be pumped to identify its contents and to prevent more of the substance from being absorbed.

People in the deepest stages of coma need a ventilator, because the brain cannot perform essential body functions, including maintenance of breathing.

Prognosis

The likelihood of recovery from a deep coma that lasts more than a few hours depends on the cause. Recovery is likely when the cause is an overdose of a sedative. When the cause is a low blood sugar level, complete recovery is possible if the brain was not deprived of sugar for more than about 1 hour. When the cause is a head injury, substantial recovery may occur, even if the coma lasts several weeks (but not if it lasts more than 3 months). When the cause is cardiac arrest or oxygen deprivation, full recovery rarely occurs if after 1 week, the person cannot move the limbs when asked to do so.

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 the person in a coma has advance medical directives, such as a living will or durable power of attorney for health care (see Section 1, Chapter 9), they should be reviewed.

A vegetative state occasionally results after severe brain damage due to a head injury, oxygen deprivation, or a severe disorder. This state results when the cerebrum, which controls thought and behavior, is destroyed, but the thalamus and brain stem, which control sleep cycles, body temperature, breathing, and heart rate, are spared. People in this state often open their eyes, and they have relatively normal sleeping and waking patterns, breathe and swallow spontaneously, and may even show a startle reaction to loud noises. However, they have lost all capacity for conscious thought and behavior, and their capacity for interacting with the environment is limited to reflex responses. Most people in a vegetative state have prominent abnormal reflexes, including stiffening or jerking of the arms and legs. If a vegetative state persists for more than a few months, recovery of consciousness is unlikely. Nevertheless, with skilled nursing care, such people can live for years.

The locked-in state is a rare condition in which people 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 severe paralysis of peripheral nerves or by strokes that affect the brain stem but not the cerebrum.

Brain death is the most severe form of unconsciousness. In this condition, the brain has permanently lost the ability to perform all vital functions, including maintenance of breathing. The person is legally dead. A widely accepted legal definition of brain death is cessation of all brain functions, even though the heart continues to beat. Established criteria for brain death include no grimacing or moving in response to painful stimulation, no reaction of the eyes to light, and the inability to breathe without assistance. If these criteria are met, the person is declared brain dead.

However, doctors cannot declare 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 low body temperature, severe abnormalities in levels of electrolytes (such as sodium) in the blood, overdose of a sedative, and ingestion of certain potentially toxic drugs.

After these medical problems are corrected, diagnostic procedures may be performed to confirm brain death. Electroencephalography (EEG--a recording of the brain's electrical activity (see Section 6, Chapter 77)) shows no brain waves if a person is brain dead. Procedures such as angiography, single photon emission computed tomography (SPECT--a procedure that uses a radioactive molecule called a radionuclide to produce images of blood flow), and Doppler ultrasonography, can show that blood is not flowing to the brain. Such procedures enable doctors to declare brain death quickly after catastrophic head injuries, as may occur in motor vehicle accidents.