The vegetative state.

The vegetative state may develop suddenly (as a consequence of traumatic or non-traumatic brain injury, such as hypoxia or anoxia; infection; or haemorrhage) or gradually (in the course of a neurodegenerative disorder, such as Alzheimer’s disease). Although uncommon, the condition is perplexing because there is an apparent dissociation between the two cardinal elements of consciousness: awareness and wakefulness. Patients in a vegetative state appear to be awake but lack any sign of awareness of themselves or their environment. Large retrospective clinical audits have shown that as many as 40% of patients with a diagnosis of vegetative state may in fact retain some level of consciousness. Misdiagnosis has many implications for a patient’s care—such as day to day management, access to early interventions, and quality of life—and has ethical and legal ramifications pertaining to decisions on the discontinuation of life supporting therapies. w2-w4 Overall, our understanding of the vegetative state is incomplete. Although we know quite a lot about the neuropathology underlying the vegetative state, our ability to assess (un)consciousness and cognitive function in the clinic is extremely limited, as highlighted by the high rate of misdiagnosis. What is the vegetative state and what is it not? The 2003 guidance from the UK’s Royal College of Physicians on diagnosing and managing the permanent vegetative state defines it as “a clinical condition of unawareness of self and environment in which the patient breathes spontaneously, has a stable circulation, and shows cycles of eye closure and opening which may simulate sleep and waking.” Three main clinical features define the vegetative state: (a) cycles of eye opening and closing, giving the appearance of sleep-wake cycles (whether the presence of eye opening and closing cycles actually reflects the presence of circadian rhythms is unclear ); (b) complete lack of awareness of the self or the environment; and (c) complete or partial preservation of hypothalamic and brain stem autonomic functions. 4 The guidelines from the Royal College of Physicians consider a vegetative state to be persistent when it lasts longer than a month and permanent when it lasts longer than six months for nontraumatic brain injuries and one year for traumatic brain injuries. Guidelines published in the United States, however, consider that for non-traumatic brain injury a permanent vegetative state exists after only three months. Although both the persistent and the permanent vegetative states are often abbreviated to “PVS,” authors of a letter in the BMJ in 2000 suggested that to avoid confusion the abbreviation should be used exclusively to indicate a permanent vegetative state. The American Congress of Rehabilitation Medicine suggested that the cause of injury (traumatic, anoxic) as well as the time elapsed since onset of the condition should be documented, as both are important for prognosis. Experts have suggested that the vegetative state should be seen as part of a continuous spectrum of conditions, often referred to as disorders of consciousness, in which someone’s wakefulness and/or awareness are impaired after severe brain injury (figure, table 1). 6 This suggestion is consistent with the idea that awareness and unawareness are part of a continuum, and it highlights the SUMMARY POINTS