A persistent vegetative state describes a person who has been in a coma but also shows signs of no longer being asleep, such as opening their eyes. However, the patient still remains unconscious and unaware of their surroundings, although they may show some response to stimulation such as touch and pain (whereas coma patients remain completely unresponsive to even severe stimuli). Individuals in a vegetative state are not legally brain dead and show brain activity on their EEG. Like coma patients, patients in a vegetative state occasionally regain full consciousness, but also like coma patients the chance of recovery decreases as the amount of time in the vegetative state increases.
Several things may cause a vegetative state, such as trauma, degenerative diseases, intracranial pressure, lack of oxygen to the brain, toxins, seizures, electrolyte imbalance, metabolism disorders and sepsis.
Diagnosing a persistent vegetative state is difficult, and it often depends on unreliable indicators, such as response to stimuli. However, the functional MRI is now coming into increasing use in diagnosis to detect cognitive functions in otherwise unresponsive patients.
A minimally conscious state may be mistaken for a vegetative state, although the former is far easier to recover from.
Although many patients recover spontaneously, there is no standard accepted treatment for the condition.