studies have shown the identification of residual cognitive function in persistent vegetative state. that is, an external stimulation, such as a painful stimulus, still activates "primary" sensory cortices in these patients but these areas are functionally disconnected from "higher order" associative areas needed for awareness. these results show that parts of the cortex are indeed still functioning in "vegetative" patients. in addition, other pet studies have revealed preserved and consistent responses in predicted regions of auditory cortex in response to intelligible speech stimuli. moreover, a preliminary fmri examination revealed partially intact responses to semantically ambiguous stimuli, which are known to tap higher aspects of speech comprehension. furthermore, several studies have used pet to assess the central processing of noxious somatosensory stimuli in patients in pvs. noxious somatosensory stimulation activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every pvs patient, even in the absence of detectable cortical evoked potentials. in conclusion, somatosensory stimulation of pvs patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. however, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices. also, there is evidence of partially functional cerebral regions in catastrophically injured brains. to study five patients in pvs with different behavioral features, researchers employed pet, mri and magnetoencephalographic (meg) responses to sensory stimulation. in three of the five patients, co-registered pet/mri correlate areas of relatively preserved brain metabolism with isolated fragments of behavior. two patients had had anoxic injuries and demonstrated marked decreases in overall cerebral metabolism to 30–40% of normal. two other patients with non-anoxic, multifocal brain injuries demonstrated several isolated brain regions with higher metabolic rates, that ranged up to 50–80% of normal. nevertheless, their global metabolic rates remained <50% of normal. meg recordings from three pvs patients provide clear evidence for the absence, abnormality or reduction of evoked responses. despite major abnormalities, however, these data also provide evidence for localized residual activity at the cortical level. each patient partially preserved restricted sensory representations, as evidenced by slow evoked magnetic fields and gamma band activity. in two patients, these activations correlate with isolated behavioral patterns and metabolic activity. remaining active regions identified in the three pvs patients with behavioral fragments appear to consist of segregated corticothalamic networks that retain connectivity and partial functional integrity. a single patient who sustained severe injury to the tegmental mesencephalon and paramedian thalamus showed widely preserved cortical metabolism, and a global average metabolic rate of 65% of normal. the relatively high preservation of cortical metabolism in this patient defines the first functional correlate of clinical–pathological reports associating permanent unconsciousness with structural damage to these regions. the specific patterns of preserved metabolic activity identified in these patients reflect novel evidence of the modular nature of individual functional networks that underlie conscious brain function. the variations in cerebral metabolism in chronic pvs patients indicate that some cerebral regions can retain partial function in catastrophically injured brains. misdiagnoses statistical pvs misdiagnosis is common. an example study with 40 patients in the united kingdom reported 43% of their patients classified as pvs were believed so and another 33% had recovered whilst the study was underway. some pvs cases may actually be a misdiagnosis of patients being in an undiagnosed minimally conscious state. since the exact diagnostic criteria of the minimally conscious state were only formulated in 2002, there may be chronic patients diagnosed as pvs before the secondary notion of the minimally conscious state became known. whether or not there is any conscious awareness with a patient's vegetative state is a prominent issue. three completely different aspects of this should be distinguished. first, some patients can be conscious simply because they are misdiagnosed (see above). in fact, they are not in vegetative states. second, sometimes a patient was correctly diagnosed but is then examined during the early stages of recovery. third, perhaps some day the notion itself of vegetative states will change so to include elements of conscious awareness. inability to disentangle these three example cases causes confusion. an example of such confusion is the response to an experiment using functional magnetic resonance imaging which revealed that a woman diagnosed with pvs was able to activate predictable portions of her brain in response to the tester's requests that she imagine herself playing tennis or moving from room to room in her house. the brain activity in response to these instructions was indistinguishable from those of healthy patients. in 2010, martin monti and fellow researchers, working at the mrc cognition and brain sciences unit at the university of cambridge, reported in an article in the new england journal of medicine that some patients in persistent vegetative states responded to verbal instructions by displaying different patterns of brain activity on fmri scans. five out of a total of 54 diagnosed patients were apparently able to respond when instructed to think about one of two different physical activities. one of these five was also able to "answer" yes or no questions, again by imagining one of these two activities. it is unclear, however, whether the fact that portions of the patients' brains light up on fmri could help these patients assume their own medical decision making. in november 2011, a publication in the lancet presented bedside eeg apparatus and indicated that its signal could be used to detect awareness in three of 16 patients diagnosed in the vegetative state. treatment currently no treatment for vegetative state exists that would satisfy the efficacy criteria of evidence-based medicine. several methods have been proposed which can roughly be subdivided into four categories: pharmacological methods, surgery, physical therapy, and various stimulation techniques. pharmacological therapy mainly uses activating substances such as tricyclic antidepressants or methylphenidate. mixed results have been reported using dopaminergic drugs such as amantadine and bromocriptine and stimulants such as dextroamphetamine. surgical methods such as deep brain stimulation are used less frequently due to the invasiveness of the procedures. stimulation techniques include sensory stimulation, sensory regulation, music and musicokinetic therapy, social-tactile interaction, and cortical stimulation. zolpidem there is limited evidence that the hypnotic drug zolpidem has an effect. the results of the few scientific studies that have been published so far on the effectiveness of zolpidem have been contradictory. epidemiology in the united states, it is estimated that there may be between 15,000 and 40,000 patients who are in a persistent vegetative state, but due to poor nursing home records exact figures are hard to determine. history the syndrome was first described in 1940 by ernst kretschmer who called it apallic syndrome. the term persistent vegetative state was coined in 1972 by scottish spinal surgeon bryan jennett and american neurologist fred plum to describe a syndrome that seemed to have been made possible by medicine's increased capacities to keep patients' bodies alive. society and culture ethics and policy an ongoing debate exists as to how much care, if any, patients in a persistent vegetative state should receive in health systems plagued by limited resources. in a case before the new jersey superior court, betancourt v. trinitas hospital, a community hospital sought a ruling that dialysis and cpr for such a patient constitutes futile care. an american bioethicist, jacob m. appel, argued that any money spent treating pvs patients would be better spent on other patients with a higher likelihood of recovery. the patient died naturally prior to a decision in the case, resulting in the court finding the issue moot. in 2010, british and belgian researchers reported in an article in the new england journal of medicine that some patients in persistent vegetative states actually had enough consciousness to "answer" yes or no questions on fmri scans. however, it is unclear whether the fact that portions of the patients' brains light up on fmri will help these patient assume their own medical decision making. professor geraint rees, director of the institute of cognitive neuroscience at university college london, responded to the study by observing that, "as a clinician, it would be important to satisfy oneself that the individual that you are communicating with is competent to make those decisions. at the moment it is premature to conclude that the individual able to answer 5 out of 6 yes/no questions is fully conscious like you or i." in contrast, jacob m. appel of the mount sinai hospital told the telegraph that this development could be a welcome step toward clarifying the wishes of such patients. appel stated: "i see no reason why, if we are truly convinced such patients are communicating, society should not honour their wishes. in fact, as a physician, i think a compelling case can be made that doctors have an ethical obligation to assist such patients by removing treatment. i suspect that, if such individuals are indeed trapped in their bodies, they may be living in great torment and will request to have their care terminated or even active euthanasia." notable cases tony bland – first patient in english legal history to be allowed to die paul brophy – first american to die after court-authorization sunny von bülow – lived almost 28 years in a persistent vegetative state until her death gustavo cerati – argentine singer-songwriter, composer and producer who died after four years in a coma prichard colón – puerto rican former professional boxer and gold medal winner who spent years in a vegetative state after a bout nancy cruzan – american woman involved in a landmark united states supreme court case gary dockery – american police officer who entered, emerged and later reentered a persistent vegetative state eluana englaro – italian woman from lecco whose life was ended after a legal case after spending 17 years in a vegetative state elaine esposito – american woman who was a previous record holder for having spent 37 years in a coma lia lee – hmong person who spent 26 years in a vegetative state and was the subject of a 1997 book by anne fadiman martin pistorius south african man who is a rare example of a survivor as his state progressed to minimally conscious after 3 years, locked in syndrome after another 4 more years, and fully came out of a coma after another 5 years. he is now a web designer, developer, and author. in 2011, he wrote a book called ghost boy, in which he describes his many years of being comatose. annie shapiro canadian woman who is also another rare example of a survivor as it is known that she could not think for her first 2 years of her 29 total years of being comatose. in 1992 she awakened fully recovered and lived her last 10 years peacefully. it is the longest a person has been in a coma and woken up apart from the catatonic stupor patients described in awakenings. haleigh poutre karen ann quinlan terri schiavo rita greene aruna shanbaug – indian woman in persistent vegetative state for 42 years until her death. owing to her case, the supreme court of india allowed passive euthanasia in the country. ariel sharon chayito valdez vice vukov helga wanglie otto warmbier