May be brief or prolonged, mild or profound.
Brief - eg fainting/syncope; Longer – eg convulsive seizure
Obtundation = reduced alertness; some unresponsiveness to touch or voice
Stupor = unresponsiveness from which can be briefly aroused to vigorous stimulus
Coma = unarousable unresponsiveness; sleep-like state of unconsciousness
Delirium & confusional states = disorientated as to place and time; confused in interpretation of sensory stimuli; may have hallucinations; short attention span; often drowsy and agitated.