Coma

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Overview

In medicine, a coma (from the Greek Template:Polytonic koma, meaning deep sleep) is a profound state of unconsciousness. A comatose patient cannot be awakened, fails to respond normally to pain or light, does not have sleep-wake cycles, and does not take voluntary actions. Coma may result from a variety of conditions, including intoxication, metabolic abnormalities, central nervous system diseases, acute neurologic injuries such as stroke, and hypoxia. It may also be deliberately induced by pharmaceutical agents in order to preserve higher brain function following another form of brain trauma, or to save the patient from extreme pain during healing of injuries or diseases. A coma may also result from immense head trauma caused by something like a car accident or a series of very severe concussions. The underlying cause of the coma is bilateral damage to the Reticular formation of the midbrain, which is important in regulating sleep .

Causes of Coma

• Acute hemorrhagic leukoencephalitis
• Addisonian crisis
• AEIOU-TIPS

  • Alcohol
  • Encephalitis
  • Insulin
  • Opiates
  • Uremia
  • Trauma
  • Infection
  • Psychiatric
  • Syncope

• Apallic Syndrome
• Biguanides
• Bilateral subdural hematoma
• Blood pressure disorders
• Brain abscess with edema
• Brain hemorrhage
• Brain tumor
• Carcinomatosis meningitis
• Cardiac dysrhythmias
• Catatonia
• Cerebral infarction with edema
• Cerebrovascular disease
• Concussion
• Congestive Heart Failure
• Consciousness shift
• Creutzfeldt-Jakob Disease
• Diabetes Insipidus
• Diabetic Acidosis
• Disseminated encephalomyelitis
• Drug withdrawal
• Drugs
• Eclampsia
• Endocarditis
• Epidural hematoma
• Focal seizures
• Hepatic coma
• Herpes encephalitis
• Hydrocephalus
• Hypercalcemia
• Hypercarbie
• Hyperkalemia
• Hypermagnesemia
• Hypernatremia
• Hyperosmolality
• Hyperphosphatemia
• Hypertensive encephalopathy
• Hyperthermia
• Hypocalcemia
• Hypoglycemia
• Hypokalemia
• Hypomagnesemia
• Hyponatremia
• Hypoosmolality
• Hypophosphatemia
• Hypothermia
• Hypothyroid crisis
• Hypoxia
• Hysterical coma
• Intracerebral hemorrhage
• Locked-In Syndrome
• Malaria
• Meningitis
• Migraine
• Narrowed consciousness
• Pheochromocytoma crisis
• Pituitary insufficiency
• Pneumonia
• Porphyria
• Postictal state
• Postoperative
• Postpartum
• Profound nutritional deficiency
• Progressive multifocal leukoencephalopathy
• Pulmonary causes
• Reye's Syndrome
• Rheumatic Fever
• Septicemia
• Severe drug overdose
• Subdural hematoma
• Thiamine deficiency
• Thrombotic Thrombocytopenic Purpura
• Thyrotoxic crisis
• Tumor with edema
• Typhoid Fever
• Wernicke's Encephalopathy

Severity

The severity of coma impairment 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.

Contrary to popular belief, a patient in a coma does not always lie still and quiet. They may move, talk, and perform other functions that may sometimes appear to be conscious acts but are not.

Two scales of measurement often used in TBI diagnosis to determine the level of coma are the Glasgow Coma Scale (GCS) and the Ranchos Los Amigos Scale (RLAS). The GCS is a simple 3 to 15-point scale (3 being the worst and 15 being that of a normal person) used by medical professionals to assess severity of neurologic trauma, and establish a prognosis. The RLAS is a more 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.

Outcome

Outcomes range from recovery to death. Comas generally last a few days to a few weeks. They rarely last more than 2 to 5 weeks but some have lasted as long as several years. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die. Some patients who have entered a vegetative state go on to regain a degree of awareness. Others remain in a vegetative state for years or even decades (the longest recorded period being 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.

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, 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 such as pneumonia 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, Terry Wallis spontaneously began speaking and regained awareness of his surroundings.

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 electrical 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.

Differential Diagnosis of Coma

Most Common Causes

• Cerebral masses
• Encephalitis
• Endocrine encephalopathies
• Heatstroke
• Intoxication
• Psychoses
• Subarachnoid hemorrhage
• Syncopes

See also

• Persistent vegetative state (vegetative coma), deep coma without detectable awareness
• Brain death (irreversible coma), irreversible end of all brain activity
• Process Oriented Coma Work, for an approach to working with residual consciousness in comatose patients

Additional Resources

• BIAUSA (Brain Injury Association of America), Types of Brain Injury.
• NINDS (National Institute of Neurological Diseases and Stroke), public domain information on TBI
• NINDS (National Institute of Neurological Diseases and Stroke), public domain information on coma

External links

• Waking coma patients with a sleeping pill
• Brain Injury Fact Sheets - Information on coma, and many other effects of brain injury.
• TBI Resource Guide Central source of information, services and products relating to brain injury, brain injury recovery, and post-acute rehabilitation.