Persistent Vegetative State - Classification

Classification

There are several definitions that vary by technical versus laymen's usage, and by legal implications in different countries.

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.

The 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 irrevocable 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 'persistent vegetative state' 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 definition of a permanent vegetative state can be made if, after exhaustive testing and a customary 12 months of observation, a medical diagnosis 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.

Note that in common usage, the "permanent" and "persistent" definitions are sometimes conflated and used interchangeably. However, the initialism "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 most recent book The Vegetative State. This is one for purposes of precision, on the grounds 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.