see also:

• the comatose patient
• verification of brain death in the ventilated patient

• the diagnosis of persistent vegetative state is difficult and usually protracted, often taking months to confirm.
• in 2004, the National Health and Medical Research Council has released advice on this matter titled Post-coma unresponsiveness (vegetative state): a clinical framework for diagnosis (pdf)

• severe damage to the thalamus and subcortical white matter (or to the cerebral cortex) but with preservation of the brainstem and the hypothalamus, such as being due to:
  • brain trauma
  • cerebral hypoxia (eg. return of spontaneous circulation (ROSC) post-arrest)

• factors that determine outcome are the cause, extent and type of brain injury, the length of time that the person has been unresponsive, and age:
  • “the prognosis for emergence is better in cases following trauma than it is after those caused by hypoxia/anoxia (most existing guidelines specify that a longer interval be allowed for assessment of post-coma unresponsiveness [VS] when it follows trauma than when it follows anoxia);”
  • “younger patients may have a better chance of emergence than older ones (especially in post-traumatic cases);”
  • “the preceding duration in coma (ie before eye opening) may provide some indication of the likelihood of emergence from a subsequent unresponsive state.”
• most will die within the 1st month
• of those who regain consciousness, most will do so before 9 months.
• those few who fail to emerge or die by 12 months have a very poor prognosis for independent living
• “After emergence from post-coma unresponsiveness (VS), there is likely to be a varying degree of disability, resulting from irreversible brain damage and other adverse effects of prolonged unresponsiveness.”

• no evidence of responsiveness to the environment;
• no evidence of purposeful responses to stimuli;
• no evidence of language comprehension or expression;
• the presence of wake-sleep cycles; and
• preserved hypothalamic and brain-stem function sufficient to ensure the maintenance of respiration and circulation.

• brain death
• degenerative conditions such as severe dementia
• congenital neurology
• treatable causes of coma such as metabolic and endocrine causes
• locked-in syndrome (usually have lesions in the ventral pons)
  • patients may be able to communicate by some residual means of motor signal, such as eye movements, a twitching muscle, or vocal sound.
• minimally conscious state
  • criteria includes one of the following:
    • following simple commands;
    • gestural or verbal yes/no responses (regardless of accuracy);
    • intelligible verbalisation;
    • purposeful behaviour including movements or affective behaviours that occur in contingent relation to relevant environmental stimuli and are not due to reflexive activity.
• severe brain damage with expressive or receptive impairments
• akinetic mutism
  • may be due to brain trauma causing lesions around the third ventricle or bilateral lesions involving the territories supplied by the anterior cerebral arteries, with infarction of the anterior cingulate gyrus or its connections.
  • trance-like state of severe but sometimes reversible unconsciousness with periods of seeming wakefulness and periods of sleep
  • sometimes recover dramatically