In the recent update of this article, the authors provide discussion of the latest research and therapies regarding persistent vegetative state. They differentiate the definitions of coma, minimally conscious state, and persistent vegetative state. They also touch on the latest ethical dilemmas involved with this condition. They highlight the importance of the role of physicians in communicating with the public about the details of the persistent vegetative state and in clarifying incorrect misconceptions that the public may have.
Historical note and terminology
The term "vegetative" refers to a passive or involuntary existence with limited cerebral activity. The term vegetative state was first described by Kretschmer, who described it as “the apallic syndrome” (Kretschmer 1940). In 1972, Jennet and Plum described the "vegetative state" as a chronic condition following diffuse brain injury that resulted in the absence of cognitive function but with the persistence of sleep-wake cycles (Jennet and Plum 1972). Individuals could open their eyes to auditory stimuli (unlike in coma) and were autonomically stable with the maintenance of respiratory and hemodynamic function. Vegetative state is differs from brain death in that brain death involves death of the brainstem whereas the vegetative state results from loss of function of the cortex with a functioning brainstem (Jennett 2003).
A vegetative state involves a complete “unawareness” of the self and the environment (Bernat 2006). It can involve a wakeful (eyes open) unawareness, especially after a coma (Noirhomme et al 2008). Those in a vegetative state can recover to a minimally conscious state, a state of poor responsiveness with reproducible and sustained awareness (Giacino 2002). At times, it has been suggested that the term “persistent vegetative state” be abandoned as this term mixes the patient's current diagnosis with long-term prognosis (persistent). There have been recommendations to change this to “minimally conscious state,” yet the definition involves a patient with an intermittent awareness of the self and environment (Giacino 2002); the minimally conscious state involves functional recovery of verbal or nonverbal communication (Noirhomme et al 2008).
The American Neurological Association Committee on Ethical Affairs and the Quality Standards Subcommittee of the American Academy of Neurology have individually defined the vegetative state as a chronic condition that preserves the ability to maintain blood pressure, respiration, and cardiac function, but not cognitive function (American Neurological Association Committee on Ethical Affairs 1993; Quality Standards Subcommittee of the American Academy of Neurology 1995). Specifically, the individual has no consciousness of self or the environment. The patient does not possess language function and, therefore, lacks any ability to communicate. Voluntary behavior or movements are absent. Facial expressions such as smiling, frowning, and crying can occur. These are not linked to any external stimulus. Sleep-wake cycles are present, but do not necessarily reflect a specific circadian rhythm and are not associated with the environment. Although medullary brainstem functions remain intact to support cardiorespiratory functions, the presence of midbrain or pontine reflexes may be variable. Spinal reflex activity also may be present, but voluntary control, such as bowel and bladder function, is absent.
The diagnosis of vegetative state can be made once the above criteria are satisfied. This condition differs from the diagnosis of persistent vegetative state in both clinical and prognostic terms. The persistent vegetative state consists of the vegetative state that continues for a duration of 1 month or longer. Persistent vegetative state does not imply permanent disability because in some cases patients can partially recover from this condition (Levin et al 1991). It is believed that after nontraumatic injuries, permanence can be determined after 6 months; after head injuries, permanence can be declared after 12 months (Jennett 2003).
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