Coma

Coma

Overview
In medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, a coma (from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

  koma, meaning deep sleep) is a state of unconsciousness
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...

, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as comatose. According to the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...

 though, a person with confusion is considered to be in the mildest coma.

Coma may result from a variety of conditions, including intoxication (such as illicit drug abuse, overdose or misuse of over the counter medications, prescribed medication, or controlled substances), metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 abnormalities, central nervous system diseases, acute neurologic injuries such as stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

s or herniations, hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

, hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

, hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

 or traumatic injuries such as head trauma caused by falls or vehicle collisions.
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Encyclopedia
In medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, a coma (from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

  koma, meaning deep sleep) is a state of unconsciousness
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...

, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as comatose. According to the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...

 though, a person with confusion is considered to be in the mildest coma.

Coma may result from a variety of conditions, including intoxication (such as illicit drug abuse, overdose or misuse of over the counter medications, prescribed medication, or controlled substances), metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 abnormalities, central nervous system diseases, acute neurologic injuries such as stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

s or herniations, hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

, hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

, hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

 or traumatic injuries such as head trauma caused by falls or vehicle collisions. It may also be deliberately induced
Induced coma
A barbiturate-induced coma, or barb coma, is a temporary coma brought on by a controlled dose of a barbiturate drug, usually pentobarbital or thiopental...

 by pharmaceutical agents in order to preserve higher brain functions following brain trauma, or to save the patient from extreme pain during healing of injuries or diseases.

In order for a patient to maintain consciousness, two important neurological components must function impeccably. The first is the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

 which is the gray matter covering the outer layer of the brain, and the other is a structure located in the brainstem, called reticular activating system
Reticular activating system
The reticular activating system is an area of the brain responsible for regulating arousal and sleep-wake transitions.- History and Etymology :...

 (RAS or ARAS). Injury to either or both of these components is sufficient to cause a patient to experience a coma. The human cortex is a group of tight, dense, "gray matter" composed of the nucleus of the neurons whose axons then form the "white matter", and is responsible for the perception of the universe, relay of the sensory input (sensation) via the thalamic pathway, and most importantly directly or indirectly in charge of all the neurological functions, from simple reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...

es to complex thinking. Reticular activating system (RAS) on the other hand is a more primitive structure in the brainstem that is tightly in connection with reticular formation
Reticular formation
The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...

 (RF), a critical anatomical structure needed for maintenance of arousal
Arousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...

 and sleep-wake transitions
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...

. Reticular activating system (RAS) takes its name from the effect it has on the reticular formation
Reticular formation
The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...

, which is via its stimulation. It is therefore necessary to investigate in a comatose patient, the integrity of the bilateral cerebral cortices, as well as that of the reticular activating system (RAS).

Signs and symptoms


Generally, a patient 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 to 8 on the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...

 is considered to be in 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 - if at all - 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
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

 (low blood sugar) or hypercapnia
Hypercapnia
Hypercapnia or hypercapnea , also known as hypercarbia, is a condition where there is too much carbon dioxide in the blood...

 (increased carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 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
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

 or subarachnoid hemorrhage
Subarachnoid hemorrhage
A subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...

 can be instantaneous. The mode of onset may therefore be indicative of the underlying cause. A state of unconsciousness lasting less than 6 hours is not by definition a coma, but a concussion, therefore a patient who loses consciousness for less than this time period should not be immediately labeled as having experienced a coma.

Diagnosis and findings


Diagnosis of coma is simple; however, diagnosing the cause of the underlying disease process often proves to be 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
Physical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...

 findings and imaging (such as CAT scan, MRI, etc.) and special studies (EEG
EEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...

, etc.)

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 the AVPU
AVPU
The AVPU scale is a system by which a first aider, ambulance crew or health care professional can measure and record a patient's responsiveness, indicating their level of consciousness....

 (alert, vocal stimuli, painful stimuli, unresponsive) scale. More elaborate scales, such as the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...

, 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
Airway management
In cardiopulmonary resuscitation, anaesthesia, emergency medicine, intensive care medicine and first aid, airway management is the process of ensuring that:# there is an open pathway between a patient’s lungs and the outside world, and...

"). If the risk of asphyxiation is deemed to be high, doctors may use various devices (such as an oropharyngeal airway
Oropharyngeal airway
An oropharyngeal airway is a medical device called an airway adjunct used to maintain a patent airway. It does this by preventing the tongue from covering the epiglottis, which could prevent the person from breathing...

, nasopharyngeal airway
Nasopharyngeal airway
In medicine, a nasopharyngeal airway, also known as an NPA or a nasal trumpet because of its flared end, a type of airway adjunct, is a tube that is designed to be inserted into the nasal passageway to secure an open airway. When a patient becomes unconscious, the muscles in the jaw commonly relax...

 or endotracheal tube) to safeguard the airway.

Physical examination findings


Physical examination is critical after stabilization. It should include vital signs
Vital signs
Vital signs are measures of various physiological statistics, often taken by health professionals, in order to assess the most basic body functions. Vital signs are an essential part of a case presentation. The act of taking vital signs normally entails recording body temperature, pulse rate ,...

, a general portion dedicated to making observations about the patient's respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...

 (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
Caloric reflex test
In medicine, the caloric reflex test is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal.-Utility:...

 test (cold caloric test), nasal tickle, corneal reflex
Corneal reflex
The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea , or bright light, though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response...

, and the gag reflex
Gag reflex
The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat, evoked by touching the soft palate or sometimes the back of the tongue. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking...

.

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 in order 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
Hyperventilation
Hyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...

 and apnea
Apnea
Apnea, apnoea, or apnœa is a term for suspension of external breathing. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged...

. 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 inspiration
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....

 and is due to a lesion of the pons
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...

. Ataxic breathing
Ataxic respiration
Ataxic respiration is an abnormal pattern of breathing characterized by complete irregularity of breathing, with irregular pauses and increasing periods of apnea. As the breathing pattern deteriorates, it merges with agonal respirations....

 is irregular and is due to a lesion (damage) of the medulla
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply 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
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...

 at the elbow, and arms adducted toward the body, with both legs extended
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...

. 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
Red nucleus
The red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...

, 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 eye lids 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
Medial longitudinal fasciculus
The medial longitudinal fasciculus is a pair of crossed fiber tracts , one on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem and are composed of both ascending and descending fibers that arise from a number of sources and terminate in different...

 (MLF) which is a brainstem nerve tract. Caloric reflex test
Caloric reflex test
In medicine, the caloric reflex test is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal.-Utility:...

 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
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

 away from this deviated position and is often seen in patients who are conscious or merely lethargic.

An important part of the physical exam is also assessment of the cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of 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
Gag reflex
The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat, evoked by touching the soft palate or sometimes the back of the tongue. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking...

 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
Corneal reflex
The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea , or bright light, though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response...

 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) Possible interpretation
ʖ 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.
ʖ "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.
ʖ One pupil is dilated and unreactive, while the other is normal (in this case the L eye is dilated but the R eye is normal in size). This could mean a damage to the oculomotor nerve
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...

 (cranial nerve number 3, CN III) on the right side, or possibility of vascular involvement.
ʖ Both pupils are dilated and unreactive to light. This could be due to overdose of certain medications, hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

 or severe anoxia
Anoxia
The term anoxia means a total decrease in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:* Anoxic waters* Anoxic event* Dead zone or hypoxic zones...

 (lack of oxygen).

Imaging and special tests findings


Imaging basically encompasses computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 (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
EEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...

 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.

History


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 will direct the appropriate therapy.

Severity and classification



Plum
Fred Plum
Fred Plum was an American neurologist who developed the terms"persistent vegetative state" and "locked-in syndrome" as part of his continuing research on consciousness and comas and care of the comatose....

 and Posner
Jerome B. Posner
Jerome B. Posner is an American neurologist and co-author of Plum and Posner's Diagnosis of Stupor and Coma. Dr. Posner has served as chief of the Neuro-Psychiatry Service of the Department of Medicine, chair of the Department of Neurology and currently occupies the George C...

 classify coma as either (1) supratentoral
Tentorium cerebelli
The tentorium cerebelli or cerebellar tentorium is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.-Anatomy:...

 (above Tentorium cerebelli
Tentorium cerebelli
The tentorium cerebelli or cerebellar tentorium is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.-Anatomy:...

), (2) infratentoral
Tentorium cerebelli
The tentorium cerebelli or cerebellar tentorium is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.-Anatomy:...

 (below Tentorium cerebelli), or (3) metabolic or (4) diffuse. 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.

The Rancho Los Amigos Scale
Rancho Los Amigos Scale
The Rancho Los Amigos Scale is a medical scale used to assess individuals after a closed head injury, including traumatic brain injury, based on cognitive and behavioural presentations as they emerge from coma...

 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.

Prognosis


Outcomes range from recovery to death. Comas can last from several days to several weeks. In more severe cases a coma may last for over 5 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
Persistent vegetative state
A persistent vegetative state is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. It is a diagnosis of some uncertainty in that it deals with a syndrome. After four weeks in a vegetative state , the patient is...

, 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 37 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
Dysarthria
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...

, 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 4 months of coma caused by brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...

, the chance of partial recovery is less than 15%, and the chance of full recovery is very low.

The most common cause of death for a person in a vegetative state is secondary infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

 such as pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

 which can occur in patients who lie still for extended periods.

Occasionally people come out of coma after long periods of time. After 19 years in a minimally conscious state
Minimally conscious state
Minimally Conscious State is a disorder of consciousness distinct from Persistent vegetative state and Locked-in syndrome. Unlike persistent vegetative state, patients with MCS have partial preservation of conscious awareness. MCS is a relatively new category of disorders of consciousness. The...

, Terry Wallis
Terry Wallis
Terry Wallis is an American man living in the Ozark Mountains of Arkansas who on June 11, 2003 regained awareness after spending almost 20 years in a minimally conscious state....

 spontaneously began speaking and regained awareness of his surroundings. Similarly, Polish
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 railroad worker Jan Grzebski
Jan Grzebski
Jan Grzebski was a Polish railroad worker who fell into a coma in 1988 and woke up in 2007. Although widely reported as a delayed effect of being hit in the head by a train's hinged car side, the coma was actually the result of a 5-centimeter brain tumor...

 woke up from a 19-year coma in 2007.

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
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...

 (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
Minimally conscious state
Minimally Conscious State is a disorder of consciousness distinct from Persistent vegetative state and Locked-in syndrome. Unlike persistent vegetative state, patients with MCS have partial preservation of conscious awareness. MCS is a relatively new category of disorders of consciousness. The...

 (MCS), a condition akin to a coma but characterized by occasional, but brief, evidence of environmental and self-awareness that coma patients lack.

Coma lasting seconds to minutes results in post-traumatic amnesia
Post-traumatic amnesia
Post-traumatic amnesia is a state of confusion that occurs immediately following a traumatic brain injury in which the injured person is disoriented and unable to remember events that occur after the injury. The person may be unable to state his or her name, where he or she is, and what time it...

 (PTA) that lasts hours to days; recovery plateau occurs over days to weeks.
Coma that lasts hours to days results in PTA lasting days to weeks; recovery plateau occurs over months.
Coma lasting weeks results in PTA that lasts months; recovery plateau occurs over months to years.

Medical treatment


Coma is a medical emergency, and 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 will be directed on preventing infections such as pneumonias, bedsores (decubitus ulcers) and providing a balanced nutrition. These infections may appear from the patient not being able to move around, and being confined to the bed. The nursing staff will move 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
Atelectasis
Atelectasis is defined as the collapse or closure of alveoli resulting in reduced or absent gas exchange. It may affect part or all of one lung. It is a condition where the alveoli are deflated, as distinct from pulmonary consolidation.It is a very common finding in chest x-rays and other...

 and pneumonia. Pneumonia can occur from the person’s inability to swallow leading to aspiration
Aspiration
Aspiration may refer to:In linguistics:*Aspirated consonant, a plosive pronounced with a strong burst of air*Debuccalization, the conversion of a consonant to [h] or [ʔ]*Voiceless glottal fricative In engine technology:...

, lack of gag reflex or from feeding tube, (aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...

). Physical therapy may also be used to prevent contractures and orthopedic deformities that would limit recovery for those patients who emerge 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 patient from falling.

Emotional challenges


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 rapport with the medical staff.

Society and culture


Research by Dr. Eelco Wijdicks on the depiction of comas in movies was published in 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
Reversal of Fortune is a 1990 film adapted from the 1985 book Reversal of Fortune: Inside the von Bülow Case, written by law professor Alan Dershowitz...

(1990) and The Dreamlife of Angels
The Dreamlife of Angels
The Dreamlife of Angels is a 1998 French drama film directed by Erick Zonca.-Story:The film is about two working class women, Isa and Marie. Isa is a drifter and searching for a lover she had met during the summer. When she realizes that her search for him is futile and turns elsewhere she meets...

(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 tanned.

See also

  • Brain death
    Brain death
    Brain death is the irreversible end of all brain activity due to total necrosis of the cerebral neurons following loss of brain oxygenation. It should not be confused with a persistent vegetative state...

     Lack of activity in both cortex, and lack of brainstem function.
  • Coma scale
    Coma scale
    A Coma scale is a system to assess the severity of coma. There are several such systems:-Glasgow Coma Scale:The Glasgow Coma Scale is neurological scale which aims to give a reliable, objective way of recording the conscious state of a person, for initial as well as continuing assessment...

    , a system to assess the severity of coma
  • Locked-in syndrome
    Locked-In syndrome
    Locked-in syndrome is a condition in which a patient is aware and awake but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for the eyes. Total locked-in syndrome is a version of locked-in syndrome where the eyes are paralyzed as...

     Paralysis of most muscles, except ocular muscles of the eyes, while patient is conscious.
  • Persistent vegetative state
    Persistent vegetative state
    A persistent vegetative state is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. It is a diagnosis of some uncertainty in that it deals with a syndrome. After four weeks in a vegetative state , the patient is...

      (vegetative coma), deep coma without detectable awareness. Damage to the cortex, with an intact brainstem.
  • Process Oriented Coma Work
    Process Oriented Coma Work
    Process Oriented Coma Work, refers to a body of theory and practice for psychotherapeutic work with patients in comatose, vegetative, and other highly withdrawn states of consciousness...

    , for an approach to working with residual consciousness in comatose patients.