Everything2 medical disclaimer
The National Institutes of Health defines a persistent vegetative state (PVS) as a syndrome with the following diagnostic criteria:
- No evidence of awareness of self
- No evidence of awareness of environment
- No ability to interact with others
- No evidence of sustained, reproducible, purposeful, or voluntary responses to visual, auditory, tactile, or noxious stimuli
- No evidence of language comprehension or expression
- Normal sleep patterns
- Sufficient hypothalmic function for survival with nursing care
- Sufficient autonomic function for survival with nursing care
- Bowel and bladder incontinence
- Variably preserved cranial-nerve reflexes
- Variably preserved spinal reflexes
- All symptoms last longer than a few weeks
Individuals in this state may sometimes exhibit response to stimuli. Patients may open their eyes in response to light. They may even ocacasionally grimace, cry, or laugh. As the definition requires, none of these responses can be sustained, reproducable, purposeful or seemingly voluntary.
The term "persistent vegetative state" was first proposed by Brian Jennet and Fred Plum in 1972 in their Lancet paper "A Syndrome in Search of a Name" to describe "wakefulness without awareness." These diagnostic citeria were defined by a multi-society task force in 1994, with representatives for the American Academy of Neurology, the Child Neurology Society, the American Neurological Association, the American Association of Neurological Surgeons, and the American Academy of Pediatrics.
PVS used to also be called permanent vegetative state, but this implied a hopelessness that was inappropriate as a few patients having displayed PVS for short whiles have recovered. PVS has also been known as apallic syndrome or severe traumatic dementia. The longer a patient suffers PVS the less likely he or she is to recover from it.
The criteria for diagnosis has fallen under criticism since its publication for the use of some vague terms such as "awareness." These terms are deliberately vague because of the difficulty of determining an internal mental state with no reliabale external cause and effect. Other tests (such as glucose metabolism, EEG, CT and PET scans) have been tried, hoping to find a measurable means of determining the state, but none has yet proven determinative.
PVS can be caused by traumatic injury, degenerative disease such as Alzheimer's and Parkinson's, or metabolic disease, which causes damage to the cortex of the brain. It is less likely that a patient can recover from PVS caused by degenerative disease.
As PVS is a syndrome caused by a variety of different possible causes, a single curative or preventative treatment is not available. Responsive treatment consists primarily of keeping the body healthy, free of pressure sores and infection. Physical therapy tries to minimize atrophy and orthopedic disformity.
How is it different from a coma?
A coma is a profound or deep state of unconsciousness, like a deep sleep. Patients in a coma never respond to external stimuli, even pain. PVS patients do respond occasionally, if unreliably. PVS may follow a coma.
How is it different from brain death?
In brain death not all autonomic functions are preserved. Specifically, breathing is maintained through artificial ventiliation. Brain dead patients are also totally unresponsive to all external stimuli, with no pupillary light reaction.
How is it different from catatonia?
Catatonia is a state of extreme body rigidity, uncontrolled activity, or extreme motor relaxation accompanied by a mental stupor. A catatonic patient's body is affected but his or her internal mental state is normal, as evidenced by post-catatonia patients' often excellent memory of the events that occured during the state.
This syndrome and its nuances was brought to the public attention in 2005 with the controversial euthanization arguments regarding Terri Schiavo, a Florida woman with 15 years of PVS.