persistent vegetative state persistent vegetative state a persistent vegetative state (pvs) or post-coma unresponsiveness (pcu) is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. after four weeks in a vegetative state (vs), the patient is classified as being in a persistent vegetative state. this diagnosis is classified as a permanent vegetative state some months (three in the us and six in the uk) after a non-traumatic brain injury or one year after a traumatic injury. the term unresponsive wakefulness syndrome may be alternatively used, as "vegetative state" has some negative connotations among the public. persistent vegetative statespecialtyneurology definition there are several definitions that vary by technical versus layman's usage. there are different legal implications in different countries. medical definition per the british royal college of physicians of london, a persistent vegetative state is "a wakeful unconscious state that lasts longer than a few weeks is referred to as a persistent (or 'continuing') vegetative state". "vegetative state" the vegetative state is a chronic or long-term condition. this condition differs from a coma: a coma is a state that lacks both awareness and wakefulness. patients in a vegetative state may have awoken from a coma, but still have not regained awareness. in the vegetative state patients can open their eyelids occasionally and demonstrate sleep-wake cycles, but completely lack cognitive function. the vegetative state is also called a "coma vigil". the chances of regaining awareness diminish considerably as the time spent in the vegetative state increases. "persistent vegetative state" persistent vegetative state is the standard usage (except in the uk) for a medical diagnosis, made after numerous neurological and other tests, that due to extensive and irreversible brain damage a patient is highly unlikely ever to achieve higher functions above a vegetative state. this diagnosis does not mean that a doctor has diagnosed improvement as impossible, but does open the possibility, in the us, for a judicial request to end life support. informal guidelines hold that this diagnosis can be made after four weeks in a vegetative state. us caselaw has shown that successful petitions for termination have been made after a diagnosis of a persistent vegetative state, although in some cases, such as that of terri schiavo, such rulings have generated widespread controversy. in the uk, the term is discouraged in favor of two more precisely defined terms that have been strongly recommended by the royal college of physicians (rcp). these guidelines recommend using a continuous vegetative state for patients in a vegetative state for more than four weeks. a medical determination of a permanent vegetative state can be made if, after exhaustive testing and a customary 12 months of observation, a medical diagnosis is made that it is impossible by any informed medical expectations that the mental condition will ever improve. hence, a "continuous vegetative state" in the uk may remain the diagnosis in cases that would be called "persistent" in the us or elsewhere. while the actual testing criteria for a diagnosis of "permanent" in the uk are quite similar to the criteria for a diagnosis of "persistent" in the us, the semantic difference imparts in the uk a legal presumption that is commonly used in court applications for ending life support. the uk diagnosis is generally only made after 12 months of observing a static vegetative state. a diagnosis of a persistent vegetative state in the us usually still requires a petitioner to prove in court that recovery is impossible by informed medical opinion, while in the uk the "permanent" diagnosis already gives the petitioner this presumption and may make the legal process less time-consuming. in common usage, the "permanent" and "persistent" definitions are sometimes conflated and used interchangeably. however, the acronym "pvs" is intended to define a "persistent vegetative state", without necessarily the connotations of permanence, and is used as such throughout this article. bryan jennett, who originally coined the term "persistent vegetative state", has now recommended using the uk division between continuous and permanent in his book the vegetative state, arguing that "the 'persistent' component of this term ... may seem to suggest irreversibility". the australian national health and medical research council has suggested "post coma unresponsiveness" as an alternative term for "vegetative state" in general. lack of legal clarity unlike brain death, permanent vegetative state (pvs) is recognized by statute law as death in only a very few legal systems. in the us, courts have required petitions before termination of life support that demonstrate that any recovery of cognitive functions above a vegetative state is assessed as impossible by authoritative medical opinion. in england, wales and scotland, the legal precedent for withdrawal of clinically assisted nutrition and hydration in cases of patients in a pvs was set in 1993 in the case of tony bland, who sustained catastrophic anoxic brain injury in the 1989 hillsborough disaster. an application to the court of protection is no longer required before nutrition and hydration can be withdrawn or withheld from pvs (or 'minimally conscious' – mcs) patients. this legal grey area has led to vocal advocates that those in pvs should be allowed to die. others are equally determined that, if recovery is at all possible, care should continue. the existence of a small number of diagnosed pvs cases that have eventually resulted in improvement makes defining recovery as "impossible" particularly difficult in a legal sense. this legal and ethical issue raises questions about autonomy, quality of life, appropriate use of resources, the wishes of family members, and professional responsibilities. signs and symptoms most pvs patients are unresponsive to external stimuli and their conditions are associated with different levels of consciousness. some level of consciousness means a person can still respond, in varying degrees, to stimulation. a person in a coma, however, cannot. in addition, pvs patients often open their eyes in response to feeding, which has to be done by others; they are capable of swallowing, whereas patients in a coma subsist with their eyes closed. cerebral cortical function (e.g. communication, thinking, purposeful movement, etc.) is lost while brainstem functions (e.g. breathing, maintaining circulation and hemodynamic stability, etc.) are preserved. non-cognitive upper brainstem functions such as eye-opening, occasional vocalizations (e.g. crying, laughing), maintaining normal sleep patterns, and spontaneous non-purposeful movements often remain intact. pvs patients' eyes might be in a relatively fixed position, or track moving objects, or move in a disconjugate (i.e., completely unsynchronized) manner. they may experience sleep-wake cycles, or be in a state of chronic wakefulness. they may exhibit some behaviors that can be construed as arising from partial consciousness, such as grinding their teeth, swallowing, smiling, shedding tears, grunting, moaning, or screaming without any apparent external stimulus. individuals in pvs are seldom on any life-sustaining equipment other than a feeding tube because the brainstem, the center of vegetative functions (such as heart rate and rhythm, respiration, and gastrointestinal activity) is relatively intact. recovery many people emerge spontaneously from a vegetative state within a few weeks. the chances of recovery depend on the extent of injury to the brain and the patient's age – younger patients having a better chance of recovery than older patients. a 1994 report found that of those who were in a vegetative state a month after a trauma, 54% had regained consciousness by a year after the trauma, whereas 28% had died and 18% were still in the vegetative state. for non-traumatic injuries such as strokes, only 14% had recovered consciousness at one year, 47% had died, and 39% were still vegetative. patients who were vegetative six months after the initial event were much less likely to have recovered consciousness a year after the event than in the case of those who were simply reported vegetative at one month. a new scientist article from 2000 gives a pair of graphs showing changes of patient status during the first 12 months after head injury and after incidents depriving the brain of oxygen. after a year, the chances that a pvs patient will regain consciousness are very low and most patients who do recover consciousness experience significant disability. the longer a patient is in a pvs, the more severe the resulting disabilities are likely to be. rehabilitation can contribute to recovery, but many patients never progress to the point of being able to take care of themselves. the medical literature also includes case reports of the recovery of a small number of patients following the removal of assisted respiration with cold oxygen. the researchers found that in many nursing homes and hospitals unheated oxygen is given to non-responsive patients via tracheal intubation. this bypasses the warming of the upper respiratory tract and causes a chilling of aortic blood and chilling of the brain which the authors believe may contribute to the person's nonresponsive state. the researchers describe a small number of cases in which removal of the chilled oxygen was followed by recovery from the pvs and recommend either warming of oxygen with a heated nebulizer or removal of the assisted oxygen if it is no longer needed. the authors further recommend additional research to determine if this chilling effect may either delay recovery or even may contribute to brain damage. there are two dimensions of recovery from a persistent vegetative state: recovery of consciousness and recovery of function. recovery of consciousness can be verified by reliable evidence of awareness of self and the environment, consistent voluntary behavioral responses to visual and auditory stimuli, and interaction with others. recovery of function is characterized by communication, the ability to learn and to perform adaptive tasks, mobility, self-care, and participation in recreational or vocational activities. recovery of consciousness may occur without functional recovery, but functional recovery cannot occur without recovery of consciousness. causes there are three main causes of pvs (persistent vegetative state): acute traumatic brain injury non-traumatic: neurodegenerative disorder or metabolic disorder of the brain severe congenital abnormality of the central nervous system potential causes of pvs are: bacterial, viral, or fungal infection, including meningitis increased intracranial pressure, such as a tumor or abscess vascular pressure which causes intracranial hemorrhaging or stroke hypoxic ischemic injury (hypotension, cardiac arrest, arrhythmia, near-drowning) toxins such as uremia, ethanol, atropine, opiates, lead, dimethylmercury, endrin, parathion, and colloidal silver physical trauma: concussion, contusion, etc. seizure, both nonconvulsive status epilepticus and postconvulsive state (postictal state) electrolyte imbalance, which involves hyponatremia, hypernatremia, hypomagnesemia, hypoglycemia, hyperglycemia, hypercalcemia, and hypocalcemia postinfectious: acute disseminated encephalomyelitis (adem) endocrine disorders such as adrenal insufficiency and thyroid disorders degenerative and metabolic diseases including urea cycle disorders, reye syndrome, and mitochondrial disease systemic infection and sepsis hepatic encephalopathy in addition, these authors claim that doctors sometimes use the mnemonic device aeiou-tips to recall portions of the differential diagnosis: alcohol ingestion and acidosis, epilepsy and encephalopathy, infection, opiates, uremia, trauma, insulin overdose or inflammatory disorders, poisoning and psychogenic causes, and shock. diagnosis despite converging agreement about the definition of persistent vegetative state, recent reports have raised concerns about the accuracy of diagnosis in some patients, and the extent to which, in a selection of cases, residual cognitive functions may remain undetected and patients are diagnosed as being in a persistent vegetative state. objective assessment of residual cognitive function can be extremely difficult as motor responses may be minimal, inconsistent, and difficult to document in many patients, or may be undetectable in others because no cognitive output is possible. in recent years, a number of studies have demonstrated an important role for functional neuroimaging in the identification of residual cognitive function in persistent vegetative state; this technology is providing new insights into cerebral activity in patients with severe brain damage. such studies, when successful, may be particularly useful where there is concern about the accuracy of the diagnosis and the possibility that residual cognitive function has remained undetected. diagnostic experiments researchers have begun to use functional neuroimaging studies to study implicit cognitive processing in patients with a clinical diagnosis of persistent vegetative state. activations in response to sensory stimuli with positron emission tomography (pet), functional magnetic resonance imaging (fmri), and electrophysiological methods can provide information on the presence, degree, and location of any residual brain function. however, use of these techniques in people with severe brain damage is methodologically, clinically, and theoretically complex and needs careful quantitative analysis and interpretation. for example, pet