Coma is characterized by the absence of arousal and thus also of consciousness. It is a state of unarousable unresponsiveness in which the patient lies with the eyes closed and has no awareness of self and surroundings [1] . A comatose patient will never open the eyes even when intensively stimulated. The patient lacks the spontaneous periods of wakefulness and eye-opening induced by stimulation that can be observed in the vegetative state. To be clearly distinguished from syncope, concussion, or other states of transient unconsciousness, coma must persist for at least one hour.
In general, comatose patients who survive begin to awaken and recover gradually within 2 to 4 weeks. This recovery may go no further than the vegetative state or the minimally conscious state, or these may be stages (brief or prolonged) on the way to more complete recovery of consciousness.



1.         Jerome B. Posner, Clifford B. Saper, Nicholas Schiff, Fred Plum The diagnosis of stupor and coma. 4th ed. Oxford University Press 2007


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