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from Ancient Greek: koma - deep sleep
German: Koma

1 Definition

A coma is the most severe degree of a quantitative disturbed consciousness or loss of consciousness. Patients in a coma are not responsive, they don't show any reaction to strong external stimuli. Spontaneous breathing remains functional but shows pathological changes in patients in a severe coma.

A comatose state is distinct from a persistent vegetative state (PVS).

2 Causes

There are various causes that can result in a coma. The most common ones are:

3 Diagnosis

Patients in a coma have closed eyes and show no reaction to

  • internal stimuli (cognitive, vegetative, emotional) and/or
  • external stimuli (painful stimuli, acoustic stimuli)

In practice, a coma can sometimes be hard to diagnose due to secondary or even tertiary causes. A guideline for differential diagnosis is the "SMASHED" mnemonic:

4 Levels of coma

Level Characteristics
1 pain stimulus causes short, targeted defense reaction; conjugate gaze; no pupillary abnormalities
2 untargeted eye movement, consensual light reflex often positive
3 no defense reactions, flexor posturing, pathological vestibulo-ocular reflex
4 no motor response, possibly decerebrate rigidity, unresponsive pupils, brain stem reflexes fail from cranial to caudal

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