Coma – Description, Types, Complications, and Prognosis


Coma, sometimes also called a persistent vegetative state, is a profound or deep state of unconsciousness. A persistent vegetative state is not brain death. An individual in a state of coma is alive but unable to move or respond to his or her environment. Coma may occur as a complication of an underlying illness, or as a result of injuries, such as head trauma. Individuals in such a state have lost their thinking abilities and awareness of their surroundings, but retain non-cognitive function and normal sleep patterns. Even though those in a persistent vegetative state lose their higher brain functions, other key functions such as breathing and circulation remain relatively intact. Spontaneous movements may occur, and the eyes may open in response to external stimuli. Individuals may even occasionally grimace, cry, or laugh. Although individuals in a persistent vegetative state may appear somewhat normal, they do not speak and they are unable to respond to commands.

Types of Coma

Types of coma can include:

  • Toxic-metabolic encephalopathy
  • Anoxic brain injury
  • Persistent vegetative state
  • Locked-in syndrome
  • Brain death
  • Medically induced


Though coma is a common clinical presentation to the emergency department (ED), the actual frequency of coma at ED presentation is difficult to determine. The number of published studies of patients presenting with coma is surprisingly small. The use of many terms to describe patients with depressed mental states leads to multiple coding options, making retrospective reviews challenging. Within a clinical record, there is often variation in assessments by different providers. Additionally, diagnostic coding frequently reflects the etiology of the altered mental status without specific coding for coma. The fact that a common cause of coma, hypoglycemia, is often treated by emergency medical service providers with resolution prior to emergency department arrival adds to coding confusion.

A more recent single-center study of over 1000 consecutive patients with coma of unknown etiology that excluded traumatic brain injury and cardiac arrest survivors found that patients with coma of unknown etiology comprised 0.4% of all ED patients. The main diagnoses were classified into acute primary brain lesions such as hemorrhage and tumors (39%), primary brain pathologies without acute lesions, largely epilepsy (25%), and pathologies that affected the brain secondarily such as sepsis, intoxications, or metabolic conditions (36%). One-third of subjects had more than one coma-explaining pathology.

What causes coma?

More than 50% of comas are related to head trauma or disturbances in the brain’s circulatory system.

Causes are many and include:

Brain injuries are caused by an accident or violence. Additionally, people can be put into a medically induced coma with medicines. This helps their brain to keep functioning after an injury and saves the patient from feeling extreme pain.

Structural brain disorders e.g. subdural or epidural traumatic hematomas, stroke, venous thrombosis, tumors, acute hydrocephalus, raised intracranial pressure, anoxic brain injury, or brainstem strokes may all cause altered mental status or coma.

Common toxic or metabolic causes include hypoglycemia, hyperglycemia, excessive alcohol intake, medication overdose, and illicit drug use.

Less common metabolic causes include hepatic encephalopathy, hyponatremia, hypernatremia, hypercalcemia, and endocrine abnormalities.

Primary central nervous system infections e.g. meningitis or encephalitis (relatively uncommon)


Symptoms of coma

  • The person looks like they’re asleep.
  • No amount of sensory stimulation can wake them up.
  • They may be breathing unusually.
  • They may be holding their body in an unusual posture.
  • Their pupils may be affected in a number of different ways. For example, one pupil is larger than the other or both pupils are constricted.

Risk factors

  • A hemorrhagic or ischemic stroke
  • A severe head injury
  • Seizures
  • Brain tumor
  • Brain infections
  • Hypoxia for a long time
  • Metabolic abnormalities, such as diabetic hyperosmolar coma, hypoglycemia
  • Toxins, including poisons, alcohol and other drugs (barbiturates, sedatives, amphetamines,cocaine)
  • Liver failure or kidney failure

Complications of Coma

The possible complicationsTrusted Source of a coma relate to the following:

  • Incompetence to respond to body stimuli, causing incontinence of the bladder and bowel
  • Inability to move, which may result in bedsores, or pressure ulcers
  • Failure to handle respiratory secretions, meaning pneumonia could develop

Doctors pay close attention to a person’s condition to prevent any secondary brain injury. This may require respiratory and cardiovascular support.

Caring for and monitoring a person in a coma

Doctors assess a person’s level of consciousness using a tool called the Glasgow Coma Scale. This level is monitored constantly for signs of improvement or deterioration. The Glasgow Coma Scale assesses three things:

Eye opening – a score of one means no eye opening, and four means opens eyes spontaneously

Verbal response to a command – a score of one means no response, and five means alert and talking

Voluntary movements in response to a command – a score of one means no response, and six means obeys commands

Most people in a coma will have a total score of eight or less. A lower score means someone may have experienced more severe brain damage and could be less likely to recover.

In the short term, a person in a coma will normally be looked after in an intensive care unit (ICU). Treatment involves ensuring their condition is stable and their body functions, such as breathing and blood pressure, are supported while the underlying cause is treated.

In the longer term, healthcare staff will give supportive treatment on a hospital ward. This can involve providing nutrition, trying to prevent infections, moving the person regularly so they don’t develop bedsores, and gently exercising their joints to stop them becoming tight.


Because people in a coma can’t express themselves, doctors must rely on physical clues and information provided by families and friends. Be prepared to provide information about the affected person, including:

  • Events leading up to the coma, such as vomiting or headaches
  • Details about how the affected person lost consciousness, including whether it occurred suddenly or over time
  • Noticeable signs or symptoms before losing consciousness
  • The affected person’s medical history, including other conditions he or she may have had in the past, such as a stroke or transient ischemic attacks
  • Recent changes in the affected person’s health or behavior
  • The affected person’s drug use, including prescription and over-the-counter medications as well as unapproved medications and illicit recreational drugs

Physical exam

The exam is likely to include:

  • Checking the affected person’s movements and reflexes, response to painful stimuli, and pupil size
  • Observing breathing patterns to help diagnose the cause of the coma
  • Checking the skin for signs of bruises due to trauma
  • Speaking loudly or pressing on the angle of the jaw or nail bed while watching for signs of arousal, such as vocal noises, eyes opening, or movement
  • Testing reflexive eye movements to help determine the cause of the coma and the location of brain damage
  • Squirting cold or warm into the affected person’s ear canals and observing eye reactions

Laboratory tests

Blood samples will be taken to check for:

  • Complete blood count
  • Electrolytes, glucose, thyroid, kidney, and liver function
  • Carbon monoxide poisoning
  • Drug or alcohol overdose

A spinal tap (lumbar puncture) can check for signs of infections in the nervous system. During a spinal tap, a doctor or specialist inserts a needle into the spinal canal and collects a small amount of fluid for analysis.

Brain scans

Imaging tests help doctors pinpoint areas of brain injury. Tests might include:

CT scan: This uses a series of X-rays to create a detailed image of the brain. A CT scan can show a brain hemorrhage, tumors, strokes and other conditions. This test is often used to diagnose and determine the cause of a coma.

MRI: This uses powerful radio waves and magnets to create a detailed view of the brain. An MRI can detect brain tissue damaged by an ischemic stroke, brain hemorrhages and other conditions. MRI scans are particularly useful for examining the brainstem and deep brain structures.

Electroencephalography (EEG): This measures the electrical activity inside the brain through small electrodes attached to the scalp. Doctors send a low electrical current through the electrodes, which record the brain’s electrical impulses. This test can determine if seizures might be the cause of a coma.

Brain scan of a coma patient


Treatment starts with reducing further damage to the brain. Physicians must clear the patient’s airways so he or she is able to breathe. In some cases, the person will have to be put on a mechanical ventilator (breathing machine).

Specific treatment will depend on the cause of the coma. For example, if the coma was caused by head trauma, efforts will be made to stop any bleeding or swelling in the brain. If the coma was caused by a disease, physicians will try to reverse it by treating the underlying condition. If poisoning caused the coma, physicians may give medications to counteract the depressive effects of the substance that caused the coma.

Once the person is treated appropriately for the immediate cause of coma, treatment will focus on supportive care. This usually includes making sure the person does not suffocate, making sure the person’s muscles and ligaments stay flexible, providing adequate nutrition, and taking precautions to help prevent infections, such as pneumonia. Because a person in a coma cannot move on his or her own, it’s important that his or her body be rotated periodically to prevent bedsores.


Comas can last from days to weeks while some severe cases have lasted several years. Recovery depends, to a considerable extent, on the original cause of the coma and on the severity of any brain damage. Some patients (e.g. patients in a diabetic coma) will make a complete recovery while others, particularly those who have suffered head trauma, may have some physical, intellectual, or psychological impairment that will require further treatment. They may need physiotherapy, occupational therapy, psychological assessment, and support during a period of rehabilitation and may need care for the rest of their lives.

The chances of someone recovering from a coma largely depend on the severity and cause of their brain injury, their age, and how long they’ve been in a coma. It’s impossible to accurately predict whether the person will eventually recover, how long the coma will last, and whether they’ll have any long-term problems.

Patients can gradually come out of the coma, some progress to a vegetative state (aka unresponsive wakefulness syndrome), and others die. Some patients who have entered a vegetative state go on to regain a degree of awareness (see Minimally Conscious State). The likelihood of significant functional improvement for coma patients diminishes over time.

Prevention of Coma

The risk of this problem may be lowered by taking steps to avoid head injury, such as:

  • Wearing a seatbelt in motor vehicles
  • Using safe, age-based sports methods for children
  • Wearing a helmet when:
  • Playing a contact sport like football, soccer, or hockey
  • Riding a bike or motorcycle
  • Using skates, scooters, and skateboards
  • Catching, batting, or running bases in baseball or softball
  • Riding a horse
  • Skiing or snowboarding

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