Coma

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Coma
Specialty Neurology, psychiatry

A coma is a deep state of prolonged 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. [1] Coma patients exhibit a complete absence of wakefulness and are unable to consciously feel, speak or move. [2] Comas can be derived by natural causes, or can be medically induced.

Unconsciousness the state, in a normally conscious being, of not being consicious

Unconsciousness is a state which occurs when the ability to maintain an awareness of self and environment is lost. It involves a complete or near-complete lack of responsiveness to people and other environmental stimuli.

An induced coma, also known as a medically induced coma, a barbiturate-induced coma, or a barb coma, is a temporary coma brought on by a controlled dose of a barbiturate drug, usually pentobarbital or thiopental. Barbiturate comas are used to protect the brain during major neurosurgery, as a last line of treatment in certain cases of status epilepticus that have not responded to other treatments, and in refractory intracranial hypertension following traumatic brain injury.

Contents

Clinically, a coma can be defined as the inability to consistently follow a one-step command. [3] It can also be defined as a score of ≤ 8 on the Glasgow Coma Scale (GCS) lasting ≥ 6 hours. For a patient to maintain consciousness, the components of wakefulness and awareness must be maintained. Wakefulness describes the quantitative degree of consciousness, whereas awareness relates to the qualitative aspects of the functions mediated by the cortex, including cognitive abilities such as attention, sensory perception, explicit memory, language, the execution of tasks, temporal and spatial orientation and reality judgment. [2] [4] From a neurological perspective, consciousness is maintained by the activation of the cerebral cortex—the gray matter that forms the outer layer of the brain and by the reticular activating system (RAS), a structure located within the brainstem. [5] [6]

The Glasgow Coma Scale (GCS) is a neurological scale which aims to give a reliable and objective way of recording the state of a person's consciousness for initial as well as subsequent assessment. A person is assessed against the criteria of the scale, and the resulting points give a person's score between 3 and either 14 or 15.

Wakefulness is a daily recurring brain state and state of consciousness in which an individual is conscious and engages in coherent cognitive and behavioral responses to the external world such as communication, ambulation, eating, and sex. Being awake is the opposite of the state of being asleep in which most external inputs to the brain are excluded from neural processing.

Consciousness state or quality of awareness or of being aware of an external object or something within oneself

Consciousness is the state or quality of awareness or of being aware of an external object or something within oneself. It has been defined variously in terms of sentience, awareness, qualia, subjectivity, the ability to experience or to feel, wakefulness, having a sense of selfhood or soul, the fact that there is something "that it is like" to "have" or "be" it, and the executive control system of the mind. Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is. As Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives." You become aware that your actions have an effect on other people.

Etymology

The term ‘coma’, from the Greek κῶμαkoma, meaning deep sleep, had already been used in the Hippocratic corpus (Epidemica) and later by Galen (second century AD). Subsequently, it was hardly used in the known literature up to the middle of the 17th century. The term is found again in Thomas Willis’ (1621–1675) influential De anima brutorum (1672), where lethargy (pathological sleep), ‘coma’ (heavy sleeping), carus (deprivation of the senses) and apoplexy (into which carus could turn and which he localized in the white matter) are mentioned. The term carus is also derived from Greek, where it can be found in the roots of several words meaning soporific or sleepy. It can still be found in the root of the term ‘carotid’. Thomas Sydenham (1624–89) mentioned the term ‘coma’ in several cases of fever (Sydenham, 1685). [7] [8]

Hippocratic Corpus literary work

The Hippocratic Corpus, or Hippocratic Collection, is a collection of around 60 early Ancient Greek medical works strongly associated with the physician Hippocrates and his teachings. Even though it is considered as a singular corpus that represents Hippocratic medicine, they vary in content, age, style, methods, and views practiced; therefore, authorship is largely unknown. Hippocrates began society's development of medicine, through a delicate blending of the art of healing and scientific observations. The Hippocratic Corpus became the foundation for which all future medical systems would be built.

Galen Roman physician, surgeon and philosopher

Aelius Galenus or Claudius Galenus, often Anglicized as Galen and better known as Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Arguably the most accomplished of all medical researchers of antiquity, Galen influenced the development of various scientific disciplines, including anatomy, physiology, pathology, pharmacology, and neurology, as well as philosophy and logic.

Thomas Willis English doctor

Thomas Willis was an English doctor who played an important part in the history of anatomy, neurology and psychiatry. He was a founding member of the Royal Society.

Signs and symptoms

Aaron in Coma1.jpg
Image of a man in a coma. [9]
Comaventilator.jpg
Image of the man still unresponsive to stimuli. [10]

General symptoms of a person in a comatose state are:

Causes

Many types of problems can cause coma. Forty percent of comatose states result from drug poisoning. [12] Drugs damage or weaken the synaptic functioning in the ascending reticular activating system (ARAS) and keep the system from properly functioning to arouse the brain. [13] 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. 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 vestibular-ocular reflex. (see Diagnosis below). [13]

Synaptic vesicle A secretory organelle, typically 50 nm in diameter, of presynaptic nerve terminals; accumulates in high concentrations of neurotransmitters and secretes these into the synaptic cleft by fusion with the active zone of the presynaptic plasma membrane

In a neuron, synaptic vesicles store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell. The area in the axon that holds groups of vesicles is an axon terminal or "terminal bouton". Up to 130 vesicles can be released per bouton over a ten-minute period of stimulation at 0.2 Hz. In the visual cortex of the human brain, synaptic vesicles have an average diameter of 39.5 nanometers (nm) with a standard deviation of 5.1 nm.

Reticular formation spinal trigeminal nucleus

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation is not anatomically well defined because it includes neurons located in different parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. The reticular formation includes ascending pathways to the cortex in the ascending reticular activating system (ARAS) and descending pathways to the spinal cord via the reticulospinal tracts of the descending reticular formation.

Vestibulo–ocular reflex reflex, where activation of the vestibular system causes eye movement

The vestibulo-ocular reflex (VOR) is a reflex, where activation of the vestibular system of the inner ear causes eye movement. This reflex functions to stabilize images on the retinas during head movement by producing eye movements in the direction opposite to head movement, thus preserving the image on the center of the visual field(s). For example, when the head moves to the right, the eyes move to the left, and vice versa. Since slight head movement is present all the time, VOR is necessary for stabilizing vision: patients whose VOR is impaired find it difficult to read using print, because they cannot stabilize the eyes during small head tremors, and also because damage to the VOR can cause vestibular nystagmus.

The second most common cause of coma, which makes up about 25% of cases, is lack of oxygen, generally resulting from cardiac arrest. [12] The Central Nervous System (CNS) requires a great deal of oxygen for its neurons. Oxygen deprivation in the brain, also known as hypoxia, causes sodium and calcium from outside of the neurons to decrease and intracellular calcium to increase, which harms neuron communication. [14] Lack of oxygen in the brain also causes ATP exhaustion and cellular breakdown from cytoskeleton damage and nitric oxide production.

Cardiac arrest sudden stop in effective blood flow due to the failure of the heart to contract effectively

Cardiac arrest is a sudden loss of blood flow resulting from the failure of the heart to effectively pump. Signs include loss of consciousness and abnormal or absent breathing. Some individuals may experience chest pain, shortness of breath, or nausea before cardiac arrest. If not treated within minutes, it typically leads to death.

Central nervous system main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges

The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord. The CNS is so named because it integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish—and it contains the majority of the nervous system. Many consider the retina and the optic nerve, as well as the olfactory nerves and olfactory epithelium as parts of the CNS, synapsing directly on brain tissue without intermediate ganglia. As such, the olfactory epithelium is the only central nervous tissue in direct contact with the environment, which opens up for therapeutic treatments. The CNS is contained within the dorsal body cavity, with the brain housed in the cranial cavity and the spinal cord in the spinal canal. In vertebrates, the brain is protected by the skull, while the spinal cord is protected by the vertebrae. The brain and spinal cord are both enclosed in the meninges. Within the CNS, the interneuronal space is filled with a large amount of supporting non-nervous cells called neuroglial cells.

Human brain Main organ of the human nervous system

The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sense organs, and making decisions as to the instructions sent to the rest of the body. The brain is contained in, and protected by, the skull bones of the head.

Twenty percent of comatose states result from the side effects of a stroke. [12] During a stroke, blood flow to part of the brain is restricted or blocked. An ischemic stroke, brain hemorrhage, or tumor may cause restriction of blood flow. Lack of blood to cells in the brain prevent oxygen from getting to the neurons, and consequently causes cells to become disrupted and die. As brain cells die, brain tissue continues to deteriorate, which may affect the 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.

List

Some examples are: [15]

Pathophysiology

Injury to either or both of the cerebral cortex or the reticular activating system (RAS) is sufficient to cause a person toenter coma.

The cerebral cortex is the outer layer of neural tissue of the cerebrum of the brain. [17] The cerebral cortex is composed of gray matter which consists of the nuclei of neurons, whereas the inner portion of the cerebrum is composed of white matter and is composed of the axons of neuron. White matter is responsible for perception, relay of the sensory input via the thalamic pathway, and many other neurological functions, including complex thinking. The RAS, on the other hand, is a more primitive structure in the brainstem which includes the reticular formation (RF). The RAS has two tracts, the ascending and descending tract. The ascending track, or ascending reticular activating system (ARAS), is made up of a system of acetylcholine-producing neurons, and works to arouse and wake up the brain. Arousal of the brain begins from the RF, through the thalamus, and then finally to the cerebral cortex. [13] A failure in ARAS functioning may thus lead to a coma.

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 underlying cause. [1]

Diagnosis

Although diagnosis of coma is simple, investigating the underlying cause of onset can be rather challenging. As such, after gaining stabilization of the patient's airways, breathing and circulation (the basic ABC s) various diagnostic tests, such as physical examinations and imaging tools (CAT scan, MRI, etc.) are employed to access the underlying cause of the coma.

When an unconscious person enters a hospital, the hospital utilizes a series of diagnostic steps to identify the cause of unconsciousness. According to Young, [13] the following steps should be taken when dealing with a patient possibly in a coma:

  1. Perform a general examination and medical history check
  2. Make sure the patient is in an actual comatose state and is not in locked-in state or experiencing psychogenic unresponsiveness. Patients with locked-in syndrome present with voluntary movement their eyes, whereas patients suffering from psychogenic comas, demonstrate active resistance to passive opening of the eyelids, with the eyelids closing abruptly and completely when the lifted upper eyelid is released (rather than slowly, asymmetrically and incompletely as seen in comas due to organic causes). [18]
  3. Find the site of the brain that may be causing coma (i.e., brainstem, back of brain…) and assess the severity of the coma with the Glasgow Coma Scale
  4. Take blood work to see if drugs were involved or if it was a result of hypoventilation/hyperventilation
  5. Check for levels of “serum glucose, calcium, sodium, potassium, magnesium, phosphate, urea, and creatinine”
  6. Perform brain scans to observe any abnormal brain functioning using either CT or MRI scans
  7. Continue to monitor brain waves and identify seizures of patient using EEG s

Initial evaluation

In the initial assessment of coma, it is common to gauge the level of consciousness on the AVPU (alert, vocal stimuli, painful stimuli, unresponsive) scale by spontaneously exhibiting actions and, assessing the patient's response to vocal and painful stimuli. More elaborate scales, such as the Glasgow Coma Scale, quantify an individual's reactions such as eye opening, movement and verbal response in order to indicate their extent of brain injury. The patient's score can vary from a score of 3 (indicating severe brain injury and death) to 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.

Imaging and testing

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, [19] 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. [20] The autonomous responses such as the skin conductance response may also provide further insight on the patient's emotional processing. [21]

Body movements

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), corneal reflex, and the gag reflex. [22] Reflexes are a good indicator of what cranial nerves are still intact and functioning and is an important part of the physical exam. 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).

Type of reflexDescription
oculocephalic reflex 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.
Pupillary light reflex 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.
Oculovestibular Reflex (Cold Caloric Test) 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.
  • The cortex is responsible for a rapid nystagmus away from this deviated position and is often seen in patients who are conscious or merely lethargic.
Corneal Reflex The corneal reflex assess the proper function of the trigeminal nerve (CN 5) and facial nerve (CN 7) and is present at infancy.
  • Lightly touching the cornea with a tissue or cotton swab induces a rapid blink reflex of both eyes.
  • Touching the sclera or eyelashes, presenting a light flash, or stimulating the supraorbital nerve will induce a less rapid but still reliable response.
  • Those in a comatose state will have altered corneal reflex depending on the severity of their unconscious and the location of their lesion. [23]
Gag Reflex The gag, or pharyngeal, reflex is centered in the medulla and consists of the reflexive motor response of pharyngeal elevation and constriction with tongue retraction in response to sensory stimulation of the pharyngeal wall, posterior tongue, tonsils, or faucial pillars.
  • This reflex is examined by touching the posterior pharynx with the soft tip of a cotton applicator and visually inspecting for elevation of the pharynx.
  • Those in comatose states will often demonstrate poor gag reflexes if there has been damage to their glossopharyngeal (CN 9) or vagus nerve (CN 10). [24]
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. Decorticate.PNG
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.

Assessment of posture and physique 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 extended. 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 posturing which indicates that the lesion is closer to the brainstem.

Pupil size

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: [5]

Pupil sizes (left eye vs. right eye)Possible interpretation
Darkblue.jpg 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.
Myosis due to opiate use.jpg "Pinpoint" pupils indicate heroin or opiate overdose, which 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. [5]
Anizokoria.JPG 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 involvement.
Cyclopentolate 1 percent Pupils.jpg Both pupils are dilated and unreactive to light. This could be due to overdose of certain medications, hypothermia or severe anoxia (lack of oxygen).

Severity

A coma can be classified as (1) supratentorial (above Tentorium cerebelli), (2) infratentorial (below Tentorium cerebelli), (3) metabolic or (4) diffused. [5] 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 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.

Treatment

Treatment for people in a coma will depend on the severity and cause of the comatose state. Upon admittance to an emergency department, coma patients will usually be placed in an Intensive Care Unit (ICU) immediately, [13] where maintenance of the patient's respiration and circulation become a first priority. Stability of their respiration and circulation is sustained through the use of intubation, ventilation, administration of intravenous fluids or blood and other supportive care as needed.

Continued care

Once a patient is stable and no longer in immediate danger, there may be a shift of priority from stabilizing the patient to maintaining the state of their physical wellbeing. Moving patients every 2–3 hours by turning them side to side is crucial to avoiding bed sores as a result of being confined to a bed. Moving patients through the use of physical therapy also aids in preventing atelectasis, contractures or other orthopedic deformities which would interfere with a coma patient's recovery. [25]

Pneumonia is also common in coma patients due to their inability to swallow which can then lead to aspiration. A coma patient's lack of a gag reflex, and use of a feeding tube can result in food, drink or other solid organic matter being lodged within their lower respiratory tract (from the trachea to the lungs). This trapping of matter in their lower respiratory tract can ultimately lead to infection, resulting in aspiration pneumonia. [25]

Coma patients may also deal with restless, or seizures. As such, soft cloth restraints may be used to prevent them from pulling on tubes or dressings and side rails on the bed should be kept up to prevent patients from falling. [25]

Caregivers

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. [26]

Prognosis

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 and in some cases, may remain in vegetative state for years or even decades (the longest recorded period being 42 years). [27] [28]

Predicted chances of recovery will differ depending on which techniques were used to measure the patient's severity of neurological damage. Predictions of recovery are based on statistical rates, expressed as the level of chance the person has of recovering. Time is the best general predictor of a chance of recovery. For example, 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 very low. [29]

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, similarly, milder comas do not ensure higher chances of recovery . 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.

Recovery

People may emerge from a coma with a combination of physical, intellectual, and psychological difficulties that need special attention. It is common for coma patients to awaken in a profound state of confusion and suffer from dysarthria, the inability to articulate any speech. Recovery usually occurs gradually. In the first days, patients may only awaken for a few minutes, with increased duration of wakefulness as their recovery progresses and may eventually recover full awareness. That said, some patients may never progress beyond very basic responses. [30]

There are reports of peopole 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 surroundings. [31]

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. [32]

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 (1990) and 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 tanned. [33]

Bioethics

A person in a coma is said to be in a unconscious state, perspectives on personhood, identity and consciousness come into play when discussing the metaphysical and bioethical views on comas.

It has been argued that unawareness should be just as ethically relevant and important as a state of awareness and that there should be metaphysical support of unawareness as a state. [34]

In the ethical discussions about disorders of consciousness (DOCs), two abilities are usually considered as central: experiencing well-being and having interests. Well-being can broadly be understood as the positive effect related to what makes life good (according to specific standards) for the individual in question. [35] The only condition for well-being broadly considered is the ability to experience its ‘positiveness’. That said, because experiencing positiveness is a basic emotional process with phylogenetic roots, it is likely to occur at a completely unaware level and therefore, introduces the idea of an unconscious well-being. [34] As such, the ability of having interests, is crucial for describing two abilities which those with comas are deficient in. Having an interest in a certain domain can be understood as having a stake in something can affect what makes our life good in that domain. An interest is what directly and immediately improves life from a certain point of view or within a particular domain, or greatly increases the likelihood of life improvement enabling the subject to realize some good. [35] That said, sensitivity to reward signals is a fundamental element in the learning process, both consciously and unconsciously. [36] Moreover, the unconscious brain is able to interact with its surroundings in a meaningful way and to produce meaningful information processing of stimuli coming from the external environment, including other people. [37]

According to Hawkins, "1. A life is good if the subject is able to value, or more basically if the subject is able to care. Importantly, Hawkins stresses that caring has no need for cognitive commitment, i.e. for high-level cognitive activities: it requires being able to distinguish something, track it for a while, recognize it over time, and have certain emotional dispositions vis-à-vis something. 2. A life is good if the subject has the capacity for relationship with others, i.e. for meaningfully interacting with other people." [35] This suggests that unawareness may (at least partly) fulfil both conditions identified by Hawkins for life to be a good for a subject, thus making the unconscious ethically relevant. [37]

See also

Related Research Articles

Head injury serious trauma to the cranium

A head injury is any injury that results in trauma to the skull or brain. The terms traumatic brain injury and head injury are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injuries, there are many causes—including accidents, falls, physical assault, or traffic accidents—that can cause head injuries.

Locked-in syndrome nervous system disease that is characterized by complete paralysis of all voluntary muscles except for the ones that control the movements of the eyes

Locked-in syndrome (LIS), also known as pseudocoma, is a condition in which a patient is aware but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for vertical eye movements and blinking. The individual is conscious and sufficiently intact cognitively to be able to communicate with eye movements. The EEG is normal in locked-in syndrome. Total locked-in syndrome, or completely locked-in state (CLIS), is a version of locked-in syndrome wherein the eyes are paralyzed as well. Fred Plum and Jerome Posner coined the term for this disorder in 1966.

Brain death is the complete loss of brain function. It differs from persistent vegetative state, in which the person is alive and some autonomic functions remain. It is also distinct from an ordinary coma, whether induced medically or caused by injury and/or illness, even if it is very deep, as long as some brain and bodily activity and function remains; and it is also not the same as the condition known as locked-in syndrome. A differential diagnosis can medically distinguish these differing conditions.

A persistent vegetative state (PVS) is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. After four weeks in a vegetative state (VS), the patient is classified as in a persistent vegetative state. This diagnosis is classified as a permanent vegetative state some months after a non-traumatic brain injury or one year after a traumatic injury. Today, doctors and neuroscientists prefer to call the state of consciousness a syndrome, primarily because of ethical questions about whether a patient can be called "vegetative" or not.

Brain damage destruction or degeneration of brain cells

Brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage, while neurotoxicity typically refers to selective, chemically induced neuron damage.

Epidural hematoma type of traumatic brain injury in which a buildup of blood occurs between the dura mater and the skull

Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain and the skull. Often there is loss of consciousness following a head injury, a brief regaining of consciousness, and then loss of consciousness again. Other symptoms may include headache, confusion, vomiting, and an inability to move parts of the body. Complications may include seizures.

Cerebral hypoxia Oxygen shortage of the brain

Cerebral hypoxia is a form of hypoxia, specifically involving the brain; when the brain is completely deprived of oxygen, it is called cerebral anoxia. There are four categories of cerebral hypoxia; they are, in order of severity: diffuse cerebral hypoxia (DCH), focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuronal cell death via apoptosis, resulting in a hypoxic brain injury.

Minimally conscious state disease

A minimally conscious state (MCS) 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 natural history and longer term outcome of MCS have not yet been thoroughly studied. The prevalence of MCS was estimated to be 112,000 to 280,000 adult and pediatric cases.

Brain herniation

Brain herniation is a potentially deadly side effect of very high pressure within the skull that occurs when a part of the brain is squeezed across structures within the skull. The brain can shift across such structures as the falx cerebri, the tentorium cerebelli, and even through the foramen magnum. Herniation can be caused by a number of factors that cause a mass effect and increase intracranial pressure (ICP): these include traumatic brain injury, intracranial hemorrhage, or brain tumor.

Cortical deafness agnosia that is a loss of the ability to perceive any auditory information but whose hearing is intact

Cortical deafness is a rare form of sensorineural hearing loss caused by damage to the primary auditory cortex. Cortical deafness is an auditory disorder where the patient is unable to hear sounds but has no apparent damage to the anatomy of the ear, which can be thought of as the combination of auditory verbal agnosia and auditory agnosia. Patients with cortical deafness cannot hear any sounds, that is, they are not aware of sounds including non-speech, voices, and speech sounds. Although patients appear and feel completely deaf, they can still exhibit some reflex responses such as turning their head towards a loud sound.

Neurointensive care branch of medicine that deals with life-threatening diseases of the nervous system

Neurocritical care is a medical field that treats life-threatening diseases of the nervous system and identifies, prevents/treats secondary brain injury.

Post-traumatic amnesia (PTA) is a state of confusion that occurs immediately following a traumatic brain injury (TBI) in which the injured person is disoriented and unable to remember events that occur after the injury. The person may be unable to state their name, where they are, and what time it is. When continuous memory returns, PTA is considered to have resolved. While PTA lasts, new events cannot be stored in the memory. About a third of patients with mild head injury are reported to have "islands of memory", in which the patient can recall only some events. During PTA, the patient's consciousness is "clouded". Because PTA involves confusion in addition to the memory loss typical of amnesia, the term "post-traumatic confusional state" has been proposed as an alternative.

Neural correlates of consciousness Bodily components, such as electrical signals, correlating to consciousness and thinking

The neural correlates of consciousness (NCC) constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious percept. Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena; that is, neural changes which necessarily and regularly correlate with a specific experience. The set should be minimal because, under the assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components is necessary to produce it.

Traumatic brain injury can cause a variety of complications, health effects that are not TBI themselves but that result from it. The risk of complications increases with the severity of the trauma; however even mild traumatic brain injury can result in disabilities that interfere with social interactions, employment, and everyday living. TBI can cause a variety of problems including physical, cognitive, emotional, and behavioral complications.

Steven Laureys is a Belgian neurologist. He is recognized worldwide as a leading clinician and researcher in the field of neurology of consciousness.

Altered level of consciousness measure of arousal other than normal

An altered level of consciousness is any measure of arousal other than normal. Level of consciousness (LOC) is a measurement of a person's arousability and responsiveness to stimuli from the environment. A mildly depressed level of consciousness or alertness may be classed as lethargy; someone in this state can be aroused with little difficulty. People who are obtunded have a more depressed level of consciousness and cannot be fully aroused. Those who are not able to be aroused from a sleep-like state are said to be stuporous. Coma is the inability to make any purposeful response. Scales such as the Glasgow coma scale have been designed to measure the level of consciousness.

Brainstem death is a clinical syndrome defined by the absence of reflexes with pathways through the brainstem—the "stalk" of the brain, which connects the spinal cord to the mid-brain, cerebellum and cerebral hemispheres—in a deeply comatose, ventilator-dependent patient. Identification of this state carries a very grave prognosis for survival; cessation of heartbeat often occurs within a few days although it may continue for weeks if intensive support is maintained.

Disorders of consciousness are medical conditions that inhibit consciousness. Some define disorders of consciousness as any change from complete self-awareness to inhibited or absent self-awareness and arousal. This category generally includes minimally conscious state and persistent vegetative state, but sometimes also includes the less severe locked-in syndrome and more severe but rare chronic coma. Differential diagnosis of these disorders is an active area of biomedical research. Finally, brain death results in an irreversible disruption of consciousness. While other conditions may cause a moderate deterioration or transient interruption of consciousness, they are not included in this category.

The FOUR Score is a clinical grading scale designed for use by medical professionals in the assessment of patients with impaired level of consciousness. It was developed by Dr. Eelco F.M. Wijdicks and colleagues in Neurocritical care at the Mayo Clinic in Rochester, Minnesota.

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