Coma is a state of unconsciousness in which a person cannot be
awakened; fails to respond normally to painful stimuli, light, or
sound; lacks a normal wake-sleep cycle; and does not initiate
voluntary actions. A person in a state of coma is described as
being comatose. A distinction is made in the medical community between
a real coma and a medically induced coma, the former is a result of
circumstances beyond the control of the medical community, while the
latter is a means by which medical professionals may allow a patient's
injuries to heal in a controlled environment.
A comatose person exhibits a complete absence of wakefulness and is
unable to consciously feel, speak, hear, or move. For a patient to
maintain consciousness, two important neurological components must
function. The first is the cerebral cortex—the gray matter that
forms the outer layer of the brain. The other is a structure located
in the brainstem, called reticular activating system (RAS).
Injury to either or both of these components is sufficient to cause a
patient to experience a coma. The cerebral cortex is a group of tight,
dense, "gray matter" composed of the nuclei of the neurons whose axons
then form the "white matter," and is responsible for perception, relay
of the sensory input via the thalamic pathway, and many other
neurological functions, including complex thinking.
RAS, on the other hand, is a more primitive structure in the brainstem
which includes the reticular formation (RF). The RAS area of the brain
has two tracts, the ascending and descending tract. Made up of a
system of acetylcholine-producing neurons, the ascending track, or
ascending reticular activating system (ARAS), works to arouse and wake
up the brain, from the RF, through the thalamus, and then finally to
the cerebral cortex. A failure in ARAS functioning may then lead to
a coma. The word is from the Greek κῶμα koma, meaning "deep
1 Signs and symptoms
1.1 Causes of coma
2.1 Diagnostic steps
2.2 Initial assessment and evaluation
Physical examination findings
2.4 Imaging and special tests findings
2.6 Severity and classification
3.1 Medical treatment
5 Society and culture
6 See also
8 External links
Signs and symptoms
Image of a man in a coma.
Image of the man still unresponsive to stimuli.
Generally, a person who is unable to voluntarily open the eyes, does
not have a sleep-wake cycle, is unresponsive in spite of strong
tactile (painful) or verbal stimuli, and who generally scores between
3 and 8 on the
Glasgow Coma Scale is considered in a coma. Coma
may have developed in humans as a response to injury to allow the body
to pause bodily actions and heal the most immediate injuries before
waking. It therefore could be a compensatory state in which the body's
expenditure of energy is not superfluous. The
severity and mode of onset of coma depends on the underlying cause.
For instance, severe hypoglycemia (low blood sugar) or hypercapnia
(increased carbon dioxide levels in the blood) initially cause mild
agitation and confusion, but progress to obtundation, stupor, and
finally, complete unconsciousness. In contrast, coma resulting from a
severe traumatic brain injury or subarachnoid hemorrhage can be
instantaneous. The mode of onset may therefore be indicative of the
Causes of coma
Coma may result from a variety of conditions, including intoxication
(such as drug abuse, overdose or misuse of over the counter
medications, prescribed medication, or controlled substances),
metabolic abnormalities, central nervous system diseases, acute
neurologic injuries such as strokes or herniations, hypoxia,
hypothermia, hypoglycemia, eclampsia or traumatic injuries such as
head trauma caused by falls, drowning accidents, or vehicle
collisions. It may also be deliberately induced by pharmaceutical
agents during major neurosurgery, to preserve higher brain functions
following brain trauma, or to save the patient from extreme pain
during healing of injuries or diseases.
Forty percent of comatose states result from drug poisoning. Drugs
damage or weaken the synaptic functioning in the ARAS and keep the
system from properly functioning to arouse the brain. Secondary
effects of drugs, which include abnormal heart rate and blood
pressure, as well as abnormal breathing and sweating, may also
indirectly harm the functioning of the ARAS and lead to a coma.
Seizures and hallucinations have shown to also play a major role in
ARAS malfunction. Given that drug poisoning is the cause for a large
portion of patients in a coma, hospitals first test all comatose
patients by observing pupil size and eye movement, through the
The second most common cause of coma, which makes up about 25% of
comatose patients, is lack of oxygen, generally resulting from cardiac
arrest. The Central Nervous System (CNS) requires a great deal of
oxygen for its neurons. Oxygen deprivation in the brain, also known as
hypoxia, causes neuronal extracellular sodium and calcium to decrease
and intracellular calcium to increase, which harms neuron
communication. Lack of oxygen in the brain also causes ATP
exhaustion and cellular breakdown from cytoskeleton damage and nitric
Twenty percent of comatose states result from the side effects of a
stroke. During a stroke, blood flow to part of the brain is
restricted or blocked. An ischemic stroke, brain hemorrhage, or tumor
may cause such cessation of blood flow. Lack of blood to cells in the
brain prevents oxygen from getting to the neurons, and consequently
causes cells to become disrupted and eventually die. As brain cells
die, brain tissue continues to deteriorate, which may affect
functioning of the ARAS.
The remaining 15% of comatose cases result from trauma, excessive
blood loss, malnutrition, hypothermia, hyperthermia, abnormal glucose
levels, and many other biological disorders.
Diagnosis of coma is simple, but diagnosing the cause of the
underlying disease process is often challenging. The first priority in
treatment of a comatose patient is stabilization following the basic
ABCs (standing for airway, breathing, and circulation). Once a person
in a coma is stable, investigations are performed to assess the
underlying cause. Investigative methods are divided into physical
examination findings and imaging (such as CAT scan, MRI, etc.) and
special studies (EEG, etc.)
When an unconscious patient enters a hospital, the hospital utilizes a
series of diagnostic steps to identify the cause of unconsciousness.
According to Young, the following steps should be taken when
dealing with a patient possibly in a coma:
Perform a general examination and medical history check
Make sure the patient is in an actual comatose state and or is not in
locked-in state (patient is either able to voluntarily move their eyes
or blink) or psychogenic unresponsiveness (caloric stimulation of the
vestibular apparatus results in slow deviation of eyes towards the
stimulation followed by rapid correction to mid-line. This response
cannot be voluntarily suppressed, so if the patient does not have this
response, psychogenic coma can be ruled out.)
Find the site of the brain that may be causing coma (i.e., brain stem,
back of brain…) and assess the severity of the coma with the Glasgow
Take blood work to see if drugs were involved or if it was a result of
Check for levels of “serum glucose, calcium, sodium, potassium,
magnesium, phosphate, urea, and creatinine”
Perform brain scans to observe any abnormal brain functioning using
either CT or
Continue to monitor brain waves and identify seizures of patient using
Initial assessment and evaluation
In the initial assessment of coma, it is common to gauge the level of
consciousness by spontaneously exhibited actions, response to vocal
stimuli ("Can you hear me?"), and painful stimuli; this is known as
AVPU (alert, vocal stimuli, painful stimuli, unresponsive) scale.
More elaborate scales, such as the Glasgow
Coma Scale, quantify an
individual's reactions such as eye opening, movement and verbal
response on a scale;
Glasgow Coma Scale (GCS) is an indication of the
extent of brain injury varying from 3 (indicating severe brain injury
and death) to a maximum of 15 (indicating mild or no brain injury).
In those with deep unconsciousness, there is a risk of asphyxiation as
the control over the muscles in the face and throat is diminished. As
a result, those presenting to a hospital with coma are typically
assessed for this risk ("airway management"). If the risk of
asphyxiation is deemed high, doctors may use various devices (such as
an oropharyngeal airway, nasopharyngeal airway or endotracheal tube)
to safeguard the airway.
Physical examination findings
Decorticate posturing, indicating a lesion at the red nucleus or
above. This positioning is stereotypical for upper brain stem, or
cortical damage. The other variant is decerebrate posturing, not seen
in this picture.
Physical examination is critical after stabilization. It should
include vital signs, a general portion dedicated to making
observations about the patient's respiration (breathing pattern), body
movements (if any), and of the patient's body habitus (physique); it
should also include assessment of the brainstem and cortical function
through special reflex tests such as the oculocephalic reflex test
(doll's eyes test), oculovestibular reflex test (cold caloric test),
nasal tickle, corneal reflex, and the gag reflex.
Vital signs in medicine are temperature (rectal is most accurate),
blood pressure, heart rate (pulse), respiratory rate, and oxygen
saturation. It should be easy to evaluate these vitals quickly to gain
insight into a patient's metabolism, fluid status, heart function,
vascular integrity, and tissue oxygenation.
Respiratory pattern (breathing rhythm) is significant and should be
noted in a comatose patient. Certain stereotypical patterns of
breathing have been identified including Cheyne–Stokes, a form of
breathing in which the patient's breathing pattern is described as
alternating episodes of hyperventilation and apnea. This is a
dangerous pattern and is often seen in pending herniations, extensive
cortical lesions, or brainstem damage. Another pattern of breathing
is apneustic breathing, which is characterized by sudden pauses of
Inhalation and is due to a lesion of the pons. Ataxic breathing
is irregular and is due to a lesion (damage) of the medulla.
Assessment of posture and body habitus is the next step. It involves
general observation about the patient's positioning. There are often
two stereotypical postures seen in comatose patients. Decorticate
posturing is a stereotypical posturing in which the patient has arms
flexed at the elbow, and arms adducted toward the body, with both legs
Decerebrate posturing is a stereotypical posturing in which
the legs are similarly extended (stretched), but the arms are also
stretched (extended at the elbow). The posturing is critical since it
indicates where the damage is in the central nervous system. A
decorticate posturing indicates a lesion (a point of damage) at or
above the red nucleus, whereas a decerebrate posturing indicates a
lesion at or below the red nucleus. In other words, a decorticate
lesion is closer to the cortex, as opposed to a decerebrate cortex
that is closer to the brainstem.
Oculocephalic reflex also known as the doll's eye is performed to
assess the integrity of the brainstem. Patient's eyelids are gently
elevated and the cornea is visualized. The patient's head is then
moved to the patient's left, to observe if the eyes stay or deviate
toward the patient's right; same maneuver is attempted on the opposite
side. If the patient's eyes move in a direction opposite to the
direction of the rotation of the head, then the patient is said to
have an intact brainstem. However, failure of both eyes to move to one
side, can indicate damage or destruction of the affected side. In
special cases, where only one eye deviates and the other does not,
this often indicates a lesion (or damage) of the medial longitudinal
fasciculus (MLF), which is a brainstem nerve tract. Caloric reflex
test also evaluates both cortical and brainstem function; cold water
is injected into one ear and the patient is observed for eye movement;
if the patient's eyes slowly deviate toward the ear where the water
was injected, then the brainstem is intact, however failure to deviate
toward the injected ear indicates damage of the brainstem on that
side. Cortex is responsible for a rapid nystagmus away from this
deviated position and is often seen in patients who are conscious or
An important part of the physical exam is also assessment of the
cranial nerves. Due to the unconscious status of the patient, only a
limited number of the nerves can be assessed. These include the
cranial nerves number 2 (CN II), number 3 (CN III), number 5 (CN V),
number 7 (CN VII), and cranial nerves 9 and 10 (CN IX, CN X). Gag
reflex helps assess cranial nerves 9 and 10. Pupil reaction to light
is important because it shows an intact retina, and cranial nerve
number 2 (CN II); if pupils are reactive to light, then that also
indicates that the cranial nerve number 3 (CN III) (or at least its
parasympathetic fibers) are intact.
Corneal reflex assess the
integrity of cranial nerve number 7 (CN VII), and cranial nerve number
5 (CN V). Cranial nerve number 5 (CN V), and its ophthalmic branch
(V1) are responsible for the afferent arm of the reflex, and the
cranial nerve number 7 (CN VII) also known a facial nerve, is
responsible for the efferent arm, causing contraction of the muscle
orbicularis oculi resulting in closing of the eyes.
Pupil assessment is often a critical portion of a comatose
examination, as it can give information as to the cause of the coma;
the following table is a technical, medical guideline for common pupil
findings and their possible interpretations:
Pupil sizes (left eye vs. right eye)
Normal eye with two pupils equal in size and reactive to light. This
means that the patient is probably not in a coma and is probably
lethargic, under influence of a drug, or sleeping.
"Pinpoint" pupils indicate heroin or opiate overdose, and can be
responsible for a patient's coma. The pinpoint pupils are still
reactive to light, bilaterally (in both eyes, not just one). Another
possibility is the damage of the pons.
One pupil is dilated and unreactive, while the other is normal (in
this case, the right eye is dilated, while the left eye is normal in
size). This could mean a damage to the oculomotor nerve (cranial nerve
number 3, CN III) on the right side, or possibility of vascular
Both pupils are dilated and unreactive to light. This could be due to
overdose of certain medications, hypothermia or severe anoxia (lack of
Imaging and special tests findings
Imaging basically encompasses computed tomography (CAT or CT) scan of
the brain, or
MRI for example, and is performed to identify specific
causes of the coma, such as hemorrhage in the brain or herniation of
the brain structures.
Special tests such as an
EEG can also show a lot
about the activity level of the cortex such as semantic
processing, presence of seizures, and are important available
tools not only for the assessment of the cortical activity but also
for predicting the likelihood of the patient's awakening. The
autonomous responses such as the skin conductance response may also
provide further insight on the patient's emotional processing.
When diagnosing any neurological condition, history and examination
are fundamental. History is obtained by family, friends or EMS. The
Glasgow Coma Scale is a helpful system used to examine and determine
the depth of coma, track patients progress and predict outcome as best
as possible. In general a correct diagnosis can be achieved by
combining findings from physical exam, imaging, and history components
and directs the appropriate therapy.
Severity and classification
A coma can be classified as (1) supratentorial (above Tentorium
cerebelli), (2) infratentorial (below Tentorium cerebelli), (3)
metabolic or (4) diffused. This classification is merely dependent
on the position of the original damage that caused the coma, and does
not correlate with severity or the prognosis. The severity of coma
impairment however is categorized into several levels. Patients may or
may not progress through these levels. In the first level, the brain
responsiveness lessens, normal reflexes are lost, the patient no
longer responds to pain and cannot hear.
Rancho Los Amigos Scale is a complex scale that has eight separate
levels, and is often used in the first few weeks or months of coma
while the patient is under closer observation, and when shifts between
levels are more frequent.
The treatment hospitals use on comatose patients depends on both the
severity and cause of the comatose state. Although the best treatment
for comatose patients remains unknown, hospitals usually place
comatose patients in an Intensive Care Unit (ICU) immediately.
Attention must first be directed to maintaining the patient's
respiration and circulation, using intubation and ventilation,
administration of intravenous fluids or blood and other supportive
care as needed. Once a patient is stable and no longer in immediate
danger, the medical staff may concentrate on maintaining the health of
patient’s physical state. The concentration is directed to
preventing infections such as pneumonias, bedsores (decubitus ulcers),
and providing balanced nutrition. Infections may appear from the
patient not being able to move around, and being confined to the bed.
The nursing staff moves the patient every 2–3 hours from side to
side and depending on the state of consciousness sometimes to a chair.
The goal is to move the patient as much as possible to try to avoid
bedsores, atelectasis and pneumonia.
Pneumonia can occur from the
person’s inability to swallow leading to aspiration, lack of gag
reflex or from feeding tube, (aspiration pneumonia). Physical therapy
may also be used to prevent contractures and orthopedic deformities
that would limit recovery for those patients who awaken from coma.
A person in a coma may become restless, or seize and need special care
to prevent them from hurting themselves. Medicine may be given to calm
such individuals. Patients who are restless may also try to pull on
tubes or dressings so soft cloth wrist restraints may be put on. Side
rails on the bed should be kept up to prevent the patient from
Methods to wake comatose patients include reversing the cause of the
coma (e.g., glucose shock if low sugar), giving medication to stop
brain swelling, or inducing hypothermia. Inducing hypothermia on
comatose patients provides one of the main treatments for patients
after suffering from cardiac arrest. In this treatment, medical
personnel expose patients to “external or intravascular cooling”
at 32-34 °C for 24 hours; this treatment cools patients down
about 2-3 °C less than normal body temperature. In 2002,
Baldursdottir and her coworkers found that in the hospital, more
comatose patients survived after induced hypothermia than patients
that remained at normal body temperature. For this reason, the
hospital chose to continue the induced hypothermia technique for all
of its comatose patients that suffered from cardiac arrest.
Coma has a wide variety of emotional reactions from the family members
of the affected patients, as well as the primary care givers taking
care of the patients. Common reactions, such as desperation, anger,
frustration, and denial are possible. The focus of the patient care
should be on creating an amicable relationship with the family members
or dependents of a comatose patient as well as creating a rapport with
the medical staff.
Comas can last from several days to several weeks. In more severe
cases a coma may last for over five weeks, while some have lasted as
long as several years. After this time, some patients gradually come
out of the coma, some progress to a vegetative state, and others die.
Some patients who have entered a vegetative state go on to regain a
degree of awareness. Others remain in a vegetative state for years or
even decades (the longest recorded period being 42 years).
The outcome for coma and vegetative state depends on the cause,
location, severity and extent of neurological damage. A deeper coma
alone does not necessarily mean a slimmer chance of recovery, because
some people in deep coma recover well while others in a so-called
milder coma sometimes fail to improve.
People may emerge from a coma with a combination of physical,
intellectual, and psychological difficulties that need special
attention. Recovery usually occurs gradually—patients acquire more
and more ability to respond. Some patients never progress beyond very
basic responses, but many recover full awareness. Regaining
consciousness is not instant: in the first days, patients are only
awake for a few minutes, and duration of time awake gradually
increases. This is unlike the situation in many movies where people
who awake from comas are instantly able to continue their normal
lives. In reality, the coma patient awakes sometimes in a profound
state of confusion, not knowing how they got there and sometimes
suffering from dysarthria, the inability to articulate any speech, and
with many other disabilities.
Predicted chances of recovery are variable owing to different
techniques used to measure the extent of neurological damage. All the
predictions are based on statistical rates with some level of chance
for recovery present: a person with a low chance of recovery may still
awaken. Time is the best general predictor of a chance of recovery:
after four months of coma caused by brain damage, the chance of
partial recovery is less than 15%, and the chance of full recovery is
The most common cause of death for a person in a vegetative state is
secondary infection such as pneumonia, which can occur in patients who
lie still for extended periods.
There are reports of patients coming out of coma after long periods of
time. After 19 years in a minimally conscious state, Terry Wallis
spontaneously began speaking and regained awareness of his
A brain-damaged man, trapped in a coma-like state for six years, was
brought back to consciousness in 2003 by doctors who planted
electrodes deep inside his brain. The method, called deep brain
stimulation (DBS) successfully roused communication, complex movement
and eating ability in the 38-year-old American man who suffered a
traumatic brain injury. His injuries left him in a minimally conscious
state (MCS), a condition akin to a coma but characterized by
occasional, but brief, evidence of environmental and self-awareness
that coma patients lack.
Comas lasting seconds to minutes result in post-traumatic amnesia
(PTA) that lasts hours to days; recovery plateau occurs over days to
weeks. Comas that last hours to days result in PTA lasting days to
weeks; recovery plateau occurs over months. Comas lasting weeks result
in PTA that lasts months; recovery plateau occurs over months to
Society and culture
Research by Dr. Eelco Wijdicks on the depiction of comas in movies was
Neurology in May 2006. Dr. Wijdicks studied 30 films
(made between 1970 and 2004) that portrayed actors in prolonged comas,
and he concluded that only two films accurately depicted the state of
a coma victim and the agony of waiting for a patient to awaken:
Reversal of Fortune
Reversal of Fortune (1990) and
The Dreamlife of Angels
The Dreamlife of Angels (1998). The
remaining 28 were criticized for portraying miraculous awakenings with
no lasting side effects, unrealistic depictions of treatments and
equipment required, and comatose patients remaining muscular and
Brain death, lack of activity in both cortex, and lack of brainstem
Coma scale, a system to assess the severity of coma
Locked-in syndrome, Paralysis of most muscles, except ocular muscles
of the eyes, while patient is conscious
Persistent vegetative state (vegetative coma), deep coma without
detectable awareness. Damage to the cortex, with an intact brainstem.
Coma Work, for an approach to working with residual
consciousness in comatose patients.
Suspended animation, the inducement of a temporary cessation or decay
of main body functions.
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^ "Video of man at beginning of documented 3 month coma".
^ "Video of man still nonresponsive to stimuli while in coma".
^ Russ Rowlett. "Glasgow
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^ Edwarda O’Bara, who spent 4 decades in a coma, dies at 59
^ Aruna Shanba, who spent 42 years in coma.
^ NINDS (October 29, 2010). "
Coma Information Page: National Institute
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Stroke (NINDS)". Retrieved
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Look up coma in Wiktionary, the free dictionary.
V · T · D
Patient UK: Coma
Disorders of consciousness
Minimally conscious state
Persistent vegetative state
Brain stem death
Symptoms and signs: cognition, perception, emotional state and
behaviour (R40–R46, 780.0–780.5, 781.1)
Persistent vegetative state
Carotid sinus syncope
Olfaction : Anosmia