Altered level of consciousness

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Altered level of consciousness
Intracerebral hemorrage (CT scan).jpg
An intracranial hemorrhage, one cause of altered level of consciousness
Specialty Psychiatry, Neurology

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. [1] A mildly depressed level of consciousness or alertness may be classed as lethargy; someone in this state can be aroused with little difficulty. [1] People who are obtunded have a more depressed level of consciousness and cannot be fully aroused. [1] [2] Those who are not able to be aroused from a sleep-like state are said to be stuporous. [1] [2] Coma is the inability to make any purposeful response. [1] [2] Scales such as the Glasgow coma scale have been designed to measure the level of consciousness.

Contents

An altered level of consciousness can result from a variety of factors, including alterations in the chemical environment of the brain (e.g. exposure to poisons or intoxicants), insufficient oxygen or blood flow in the brain, and excessive pressure within the skull. Prolonged unconsciousness is understood to be a sign of a medical emergency. [3] A deficit in the level of consciousness suggests that both of the cerebral hemispheres or the reticular activating system have been injured. [4] A decreased level of consciousness correlates to increased morbidity (sickness) and mortality (death). [5] Thus it is a valuable measure of a patient's medical and neurological status. In fact, some sources consider level of consciousness to be one of the vital signs. [3] [6]

Definition

Scales and terms to classify the levels of consciousness differ, but in general, reduction in response to stimuli indicates an altered level of consciousness:

Levels of consciousness
LevelSummary (Kruse) [2] Description
Metaconscious PreternaturalPeople who possess the ability to monitor and control their own cognitive processes in addition to meeting all the criteria indicative of a normal level of consciousness. In the field of cognitive neuroscience, metacognitive monitoring and control have been viewed as functions of the prefrontal cortex, which receives sensory input signals from divergent cortical regions and implements control through feedback loops which are established utilizing the underlying mechanisms of neuroplasticity (see chapters by Schwartz & Bacon and Shimamura, in Dunlosky & Bjork, 2008). [7]
Conscious NormalAssessment of LOC involves checking orientation: people who are able promptly and spontaneously to state their name, location, and the date or time are said to be oriented to self, place, and time, or "oriented X3". [8] A normal sleep stage from which a person is easily awakened is also considered a normal level of consciousness. [9] "Clouding of consciousness" is a term for a mild alteration of consciousness with alterations in attention and wakefulness. [9]
Confused Disoriented; impaired thinking and responsesPeople who do not respond quickly with information about their name, location, and the time are considered "obtuse" or "confused". [8] A confused person may be bewildered, disoriented, and have difficulty following instructions. [9] The person may have slow thinking and possible memory time loss. This could be caused by sleep deprivation, malnutrition, allergies, environmental pollution, drugs (prescription and nonprescription), and infection.
Delirious Disoriented; restlessness, hallucinations, sometimes delusionsSome scales have "delirious" below this level, in which a person may be restless or agitated and exhibit a marked deficit in attention. [2]
Somnolent SleepyA somnolent person shows excessive drowsiness and responds to stimuli only with incoherent mumbles or disorganized movements. [8]
Obtunded Decreased alertness; slowed psychomotor responsesIn obtundation , a person has a decreased interest in their surroundings, slowed responses, and sleepiness. [9]
Stuporous Sleep-like state (not unconscious); little/no spontaneous activityPeople with an even lower level of consciousness, stupor, only respond by grimacing or drawing away from painful stimuli. [8]
Comatose Cannot be aroused; no response to stimuliComatose people do not even make this response to stimuli, have no corneal or gag reflex, and they may have no pupillary response to light. [8]

Altered level of consciousness is sometimes described as altered sensorium.

Glasgow Coma Scale

The most commonly used tool for measuring LOC objectively is the Glasgow Coma Scale (GCS). It has come into almost universal use for assessing people with brain injury, [2] or an altered level of consciousness. Verbal, motor, and eye-opening responses to stimuli are measured, scored, and added into a final score on a scale of 3–15, with a lower score being a more decreased level of consciousness.

Others

The AVPU scale is another means of measuring LOC: people are assessed to determine whether they are alert, responsive to verbal stimuli, responsive to painful stimuli, or unresponsive. [3] [6] To determine responsiveness to voice, a caregiver speaks to, or, failing that, yells at the person. [3] Responsiveness to pain is determined with a mild painful stimulus such as a pinch; moaning or withdrawal from the stimulus is considered a response to pain. [3] The ACDU scale, like AVPU, is easier to use than the GCS and produces similarly accurate results. [10] Using ACDU, a patient is assessed for alertness, confusion, drowsiness, and unresponsiveness. [10]

The Grady Coma Scale classes people on a scale of I to V along a scale of confusion, stupor, deep stupor, abnormal posturing, and coma. [9]

Pathophysiology

Although the neural science behind alertness, wakefulness, and arousal are not fully known, the reticular formation is known to play a role in these. [9] The ascending reticular activating system is a postulated group of neural connections that receives sensory input and projects to the cerebral cortex through the midbrain and thalamus from the reticular formation. [9] Since this system is thought to modulate wakefulness and sleep, interference with it, such as injury, illness, or metabolic disturbances, could alter the level of consciousness. [9]

Normally, stupor and coma are produced by interference with the brain stem, such as can be caused by a lesion or indirect effects, such as brain herniation. [9] Mass lesions in the brain stem normally cause coma due to their effects on the reticular formation. [11] Mass lesions that occur above the tentorium cerebelli normally do not significantly alter the level of consciousness unless they are very large or affect both cerebral hemispheres. [9]

Diagnosis

Assessing LOC involves determining an individual's response to external stimuli. [12] Speed and accuracy of responses to questions and reactions to stimuli such as touch and pain are noted. [12] Reflexes, such as the cough and gag reflexes, are also means of judging LOC. [12] Once the level of consciousness is determined, clinicians seek clues for the cause of any alteration. [9] Usually the first tests in the ER are pulse oximetry to determine if there is hypoxia, serum glucose levels to rule out hypoglycemia. A urine drug screen may be sent. A CT head is very important to obtain to rule out bleed. In cases where meningitis is suspected, a lumbar puncture must be performed. A serum TSH is an important test to order. In select groups consider vitamin B12 levels. Checking serum ammonia is particularly advised in neonatal coma to discern inborn errors of metabolism.

Differential diagnosis

A lowered level of consciousness indicate a deficit in brain function. [4] Level of consciousness can be lowered when the brain receives insufficient oxygen (as occurs in hypoxia); insufficient blood (as occurs in shock, in children for example due to intussusception); or has an alteration in the brain's chemistry. [3] Conditions of the heart and conditions of the lungs can alter consciousness. Metabolic disorders such as diabetes mellitus and uremia can alter consciousness. [12] Hypo- or hypernatremia (decreased and elevated levels of sodium, respectively) as well as dehydration can also produce an altered LOC. [13] A pH outside of the range the brain can tolerate will also alter LOC. [9] Exposure to drugs (e.g. alcohol) or toxins may also lower LOC, [3] as may a core temperature that is too high or too low (hyperthermia or hypothermia). Increases in intracranial pressure (the pressure within the skull) can also cause altered LOC. It can result from traumatic brain injury such as concussion. [12] Ischemic stroke and brain bleeding are other causes of altered consciousness. [12] Infections of the central nervous system may also be associated with decreased LOC; for example, an altered LOC is the most common symptom of encephalitis. [14] Neoplasms within the intracranial cavity can also affect consciousness, [12] as can epilepsy and post-seizure states. [9] A decreased LOC can also result from a combination of factors. [12] A concussion, which is a mild traumatic brain injury (MTBI) may result in decreased LOC.

Treatment

Treatment depends on the degree of decrease in consciousness and its underlying cause. Initial treatment often involves the administration of dextrose if the blood sugar is low as well as the administration of oxygen, naloxone and thiamine.

See also

Related Research Articles

<span class="mw-page-title-main">Consciousness</span> Awareness of internal and external existence

Consciousness, at its simplest, is awareness of internal and external existence. However, its nature has led to millennia of analyses, explanations and debate by philosophers, theologians, and all of science. Opinions differ about what exactly needs to be studied or even considered consciousness. In some explanations, it is synonymous with the mind, and at other times, an aspect of mind. In the past, it was one's "inner life", the world of introspection, of private thought, imagination and volition. Today, it often includes any kind of cognition, experience, feeling or perception. It may be awareness, awareness of awareness, or self-awareness either continuously changing or not. The disparate range of research, notions and speculations raises a curiosity about whether the right questions are being asked.

<span class="mw-page-title-main">Coma</span> State of unconsciousness

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. The person may experience respiratory and circulatory problems due to the body's inability to maintain normal bodily functions. People in a coma often require extensive medical care to maintain their health and prevent complications such as pneumonia or blood clots. Coma patients exhibit a complete absence of wakefulness and are unable to consciously feel, speak or move. Comas can be derived by natural causes, or can be medically induced.

The Glasgow Coma Scale (GCS) is a clinical scale used to reliably measure a person's level of consciousness after a brain injury.

A vegetative state (VS) or post-coma unresponsiveness (PCU), 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, the patient is classified as being in a persistent vegetative state (PVS). This diagnosis is classified as a permanent vegetative state some months after a non-traumatic brain injury or one year after a traumatic injury. The term unresponsive wakefulness syndrome may be alternatively used, as "vegetative state" has some negative connotations among the public.

<span class="mw-page-title-main">Brain damage</span> Destruction or degeneration of brain cells

Neurotrauma, 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.

<span class="mw-page-title-main">Arousal</span> State of being awoken

Arousal is the physiological and psychological state of being awoken or of sense organs stimulated to a point of perception. It involves activation of the ascending reticular activating system (ARAS) in the brain, which mediates wakefulness, the autonomic nervous system, and the endocrine system, leading to increased heart rate and blood pressure and a condition of sensory alertness, desire, mobility, and reactivity.

Sopor is a condition of abnormally deep sleep, similar to a stupor but not as severe, from which it is difficult to rouse a person. It involves a profound depression of consciousness, which is manifested by drowsiness, while maintaining coordinated defensive reactions to stimuli such as pain, harsh sound, and bright light, and preserving vital functions. Sopor may be caused by a drug; such drugs are deemed soporific. A stupor is more severe than a sopor.

In the anatomy of the brain, the centromedian nucleus, also known as the centrum medianum, is a part of the intralaminar thalamic nuclei (ITN) in the thalamus. There are two centromedian nuclei arranged bilaterally.

The AVPU scale is a system by which a health care professional can measure and record a patient's level of consciousness. It is mostly used in emergency medicine protocols, and within first aid.

<span class="mw-page-title-main">Reticular formation</span> Spinal trigeminal nucleus

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It 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.

<span class="mw-page-title-main">Stupor</span> Medical condition

Stupor is the lack of critical mental function and a level of consciousness, in which an affected person is almost entirely unresponsive and responds only to intense stimuli such as pain. The word derives from the Latin stupor.

Obtundation is mild to moderate alertness reduction with decreased interest in the environment and slower than normal reactivity to stimulation. It is distinguished from the much stronger states of unresponsiveness of stupor and coma. Obtundation typically occurs as a result of a medical condition or trauma.

<span class="mw-page-title-main">Neural correlates of consciousness</span> Neuronal events sufficient for a specific conscious percept

The neural correlates of consciousness (NCC) refer to the relationships between mental states and neural states and 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 materialist assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components are necessary to produce it.

Emotional responsivity is the ability to acknowledge an affective stimuli by exhibiting emotion. It is a sharp change of emotion according to a person's emotional state. Increased emotional responsivity refers to demonstrating more response to a stimulus. Reduced emotional responsivity refers to demonstrating less response to a stimulus. Any response exhibited after exposure to the stimulus, whether it is appropriate or not, would be considered as an emotional response. Although emotional responsivity applies to nonclinical populations, it is more typically associated with individuals with schizophrenia and autism.

The National Institutes of Health Stroke Scale, or NIH Stroke Scale (NIHSS), is a tool used by healthcare providers to objectively quantify the impairment caused by a stroke and aid planning post-acute care disposition, though was intended to assess differences in interventions in clinical trials. The NIHSS was designed for the National Institute of Neurological Disorders and Stroke (NINDS) Recombinant Tissue Plasminogen Activator (rt-PA) for Acute Stroke Trial and was first published by neurologist Dr. Patrick Lyden and colleagues in 2001. Prior to the NIHSS, during the late 1980s, several stroke-deficit rating scales were in use.

Emotional lateralization is the asymmetrical representation of emotional control and processing in the brain. There is evidence for the lateralization of other brain functions as well.

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.

Reinforcement sensitivity theory (RST) proposes three brain-behavioral systems that underlie individual differences in sensitivity to reward, punishment, and motivation. While not originally defined as a theory of personality, the RST has been used to study and predict anxiety, impulsivity, and extraversion. The theory evolved from Gray's biopsychological theory of personality to incorporate findings from a number of areas in psychology and neuroscience, culminating in a major revision in 2000. The revised theory distinguishes between fear and anxiety and proposes functionally related subsystems. Measures of RST have not been widely adapted to reflect the revised theory due to disagreement over related versus independent subsystems. Despite this controversy, RST informed the study of anxiety disorders in clinical settings and continues to be used today to study and predict work performance. RST, built upon Gray's behavioral inhibition system (BIS) and behavioral activation system (BAS) understanding, also may help to suggest predispositions to and predict alcohol and drug abuse. RST, a continuously evolving paradigm, is the subject of multiple areas of contemporary psychological enquiry.

Pain stimulus is a technique used by medical personnel for assessing the consciousness level of a person who is not responding to normal interaction, voice commands or gentle physical stimuli. It forms one part of a number of neurological assessments, including the first aid based AVPU scale and the more medically based Glasgow Coma Scale.

<span class="mw-page-title-main">Tristan Bekinschtein</span>

Tristan Bekinschtein is biologist, Master in Neurophysiology and PhD in neuroscience, Buenos Aires University. He is a university lecturer and Turing Fellow at Cambridge University. Dr. Bekinschtein is primarily known for his work on variable states of consciousness and auditory feedback. He presently runs the Consciousness and Cognition Laboratory at Cambridge University.

References

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  4. 1 2 Porth, p. 838
  5. ↑ Scheld et al.. p. 530
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  11. ↑ Tindall SC (1990). "Level of consciousness". In Walker HK, Hall WD, Hurst JW (eds.). Clinical Methods: The History, Physical, and Laboratory Examinations. Butterworth Publishers. ISBN   9780409900774. PMID   21250221 . Retrieved 2008-07-04. Mass lesions within monkey coma by virtue of direct effects on the reticular formation of monkey
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  13. ↑ Johnson AF, Jacobson BH (1998). Medical Speech-language Pathology: A Practitioner's Guide. Stuttgart: Thieme. p. 142. ISBN   0-86577-688-1 . Retrieved 2008-07-04.
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