Disorders of consciousness

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Disorders of consciousness are medical conditions that inhibit consciousness.[1] Some define disorders of consciousness as any change from complete self-awareness to inhibited or absent self-awareness. This category generally includes minimally conscious state and persistent vegetative state, but sometimes also includes the less severe locked-in syndrome and more severe chronic coma.[1][2] Differential diagnosis of these disorders is an active area of biomedical research.[3][4][5] Finally, brain death results in an irreversible disruption of consciousness.[1] While other conditions may cause a moderate deterioration (e.g., dementia and delirium) or transient interruption (e.g., grand mal and petit mal seizures) of consciousness, they are not included in this category.

Classification[edit]

Locked-in syndrome[edit]

Main article: Locked-in syndrome

In locked-in syndrome the patient has awareness, sleep-wake cycles, and meaningful behavior (viz., eye-movement), but is isolated due to quadriplegia and pseudobulbar palsy. 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 well.[6]

Minimally conscious state[edit]

In a minimally conscious state, the patient has intermittent periods of awareness and wakefulness and displays some meaningful behavior.

Persistent vegetative state[edit]

In a persistent vegetative state, the patient has sleep-wake cycles, but lacks awareness and only displays reflexive and non-purposeful behavior. It is a diagnosis of some uncertainty in that it deals with a syndrome. 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 (PVS) after approximately 1 year of being in a vegetative state.

Chronic coma[edit]

Main article: Chronic coma

In chronic coma the patient lacks awareness and sleep-wake cycles and only displays reflexive behavior. In medicine, a coma (from the Greek κῶμα koma, meaning deep sleep) is a state of unconsciousness, lasting more than six hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light, sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as comatose. Although, according to the Glasgow Coma Scale, a person with confusion is considered to be in the mildest coma.

Although a coma patient may appear to be awake, they are unable to consciously feel, speak, hear, or move. For a patient to maintain consciousness, two important neurological components must function impeccably. The first is the cerebral cortex which is the gray matter covering the outer layer of the brain. The other is a structure located in the brainstem, called reticular activating system (RAS or ARAS). Injury to either or both of these components is sufficient to cause a patient to experience a coma.

Brain death[edit]

Main article: Brain death

Brain death is the irreversible end of all brain activity, and function (including involuntary activity necessary to sustain life). The main cause is total necrosis of the cerebral neurons following loss of brain oxygenation. After brain death the patient lacks any sense of awareness; sleep-wake cycles or behavior, and typically look as if they are dead or are in a deep sleep-state or coma. Although visually similar to a comatose state such as persistent vegetative state, the two should not be confused. Patients classified as brain dead are legally dead and can qualify as organ donors, in which their organs are surgically removed and prepared for a particular recipient.

Brain death is one of the deciding factors when pronouncing a trauma patient as dead. Determining function and presence of necrosis after trauma to the whole brain or brain-stem may be used to determine brain death, and is used in many states in the US.

See also[edit]

References[edit]

  1. ^ a b c Bernat JL (8 Apr 2006). "Chronic disorders of consciousness". Lancet 367 (9517): 1181–1192. doi:10.1016/S0140-6736(06)68508-5. PMID 16616561. 
  2. ^ Bernat JL (20 Jul 2010). "The natural history of chronic disorders of consciousness". Neurol 75 (3): 206–207. doi:10.1212/WNL.0b013e3181e8e960. PMID 20554939. 
  3. ^ Coleman MR, Davis MH, Rodd JM, Robson T, Ali A, Owen AM, Pickard JD (Sep 2009). "Towards the routine use of brain imaging to aid the clinical diagnosis of disorders of consciousness". Brain 132 (9): 2541–2552. doi:10.1093/brain/awp183. PMID 19710182. 
  4. ^ Monti MM, Vanhaudenhuyse A, Coleman MR, Boly M, Pickard JD, Tshibanda L, Owen AM, Laureys S (18 Feb 2010). "Willful modulation of brain activity in disorders of consciousness". N Engl J Med 362 (7): 579–589. doi:10.1056/NEJMoa0905370. PMID 20130250. 
  5. ^ Seel RT, Sherer M, Whyte J, Katz DI, Giacino JT, Rosenbaum AM, Hammond FM, Kalmar K, Pape TL et al. (Dec 2010). "Assessment scales for disorders of consciousness: evidence-based recommendations for clinical practice and research". Arch Phys Med Rehabil 91 (12): 1795–1813. doi:10.1016/j.apmr.2011.01.002. PMID 21112421. 
  6. ^ Bauer, G. and Gerstenbrand, F. and Rumpl, E. (1979). "Varieties of the locked-in syndrome". Journal of Neurology 221 (2): 77–91. doi:10.1007/BF00313105. PMID 92545.