- First published: January 19, 2025
- Page modified: September 17, 2025
“What has rehabilitation to do with people with a prolonged disorder of consciousness (PDOC)? Surely, there is nothing you can do to help them?” These questions may not be asked often, but many people will ask themselves, which is unsurprising. The questions partially reflect a narrow view of rehabilitation as something that “helps disabled people get better.” Others who better understand rehabilitation’s scope worry about resources devoted to a few people or do not appreciate the satisfaction and stimulation one can gain. There is also the practical answer: no one else accepts any responsibility for this needy population, and rehabilitation has responded by taking responsibility. Not all rehabilitation professionals agree. In this introduction and history page, I will explore some issues and expound on some benefits that will be covered later.
Table of Contents
PDOC: introduction and history
The official UK definition of a prolonged disorder of consciousness is “Patients with PDOC are those who remain in a state of wakefulness but absent or reduced awareness (i.e. in a vegetative or minimally conscious state) for more than 4 weeks.”. Many people are more familiar with other terms such as the minimally conscious state, the vegetative state, coma, unresponsive wakefulness, and other less frequently used terms. All refer to a person with a prolonged disorder of consciousness.
Prolonged disorder of consciousness, abbreviated to PODC, is a better term because it acknowledges that (un)consciousness encompasses a range of behaviours and degrees of arousal. It also avoids time-wasting confusion arising from invalid distinctions that detract from more significant issues.
The National Guideline also introduces a category of Terminal Disorder of Consciousness for people who become unconscious before dying. This is not very helpful because almost everyone becomes unconscious before all signs of life end, and many people with dementia, Huntington’s Disease, Parkinson’s Disease, etc, may be unconscious for years before dying.
The focus on defining states and different types of disorders of consciousness arises for historical reasons. History also explains many other managements that, looked at dispassionately, seem irrational or inexplicable.
Therefore, this introductory page will review the development of an interest in patients with a prolonged disorder of consciousness. The review will touch on many issues, which will be covered in more detail later.
PDOC: history – origins. (pre-1972)
This part mainly draws on two texts:
- The historical origins of the vegetative state: Received wisdom and the utility of the text, by Zoe Adams and Joseph Fins 2016. It is also accessible here.
- Disorders of Consciousness Classification and Taxonomy, by Katerine Golden et al. (2024)
Aristotle (400 BCE) distinguished between two aspects of human function: the vegetative faculty, which is essential and likened to the nutritive faculty of plants, and other aspects of the psyche, including sensation, movement, and thought.
This distinction was further developed in 1800 AD by Xavier Bichate in a manuscript entitled Recherches Physiologiques sur la vie et la Mort. In it, he refers to the brain’s animalic (vie de relation) and vegetative (vie de nutrition) functions.
In vegetative bodily functions, he did not only refer to the brain; he also included digestive, respiratory, and other systems. Animal life was considered responsible for intellectual acts that required understanding. Walter Timme developed the idea of vegetative functions in 1928 to account for autonomic nervous actions outside conscious control.
The term the apallic syndrome was used in 1940 by E Kretschmer to describe people who were awake (i.e. opened their eyes with a diurnal sleep-wake rhythm) but were unresponsive. In 1963, M Arnaud and colleagues published Etats frontières entre la vie et la mort en neuro-traumatologie and referred to the vegetative of people who were still unconscious after brain trauma but were opening their eyes.
Last, in 1972, Bryan Jennett and Fred Plum published the seminal paper, “Persistent vegetative state after brain damage: a syndrome in search of a name.” This paper described a group of patients who were awake but not conscious.
In summary, a distinction between the many bodily functions that were not under conscious control and higher-order mental functions has existed for over 200 years. As medical practice improved, a group of people survived severe brain injury but did not regain consciousness. The apallic syndrome was perhaps the first specific term used for this group of patients. Still, the term vegetative predated its use and was eventually strongly associated with the condition in 1972.
PDOC: terminological explosion. 1972-2020
About 538 million years ago, the Cambrian evolutionary explosion occurred when life suddenly could adapt to a new environment.
A similar phenomenon occurred with the recognition of “a syndrome in search of a name”; it initiated an explosion of terms; some identified specific characteristics, others reflected the local culture, and some were similar terms used for similar states. Many terms have since died out or remain used by only a few people. I will cover a few of the terms used.
The vegetative state rapidly became the general term used for people left unconscious after trauma or disease. Within a few years, families of people left in a vegetative state began asking for treatment to be withdrawn, and the term acquired great medico-legal and ethical significance. One pivotal case in the United States was Nancy Cruzan, whose case was heard in 1990 by the US Supreme Court (see Persistent Vegetative State and the Right to Die: the United States and Britain, by Bryan Jennett and Clare Dyer).
The legal and ethical process increased clinical attention to the state of a patient’s consciousness, particularly absolute unawareness. People soon appreciated that unconsciousness varied; for example, an early document from the Royal Hospital for Neuro-disability (lead author Professor Keith Andrews) suggested four or five levels (Report, International Working Party Report on the Vegetative State).
The terms used include:
- Permanent vegetative state and persistent vegetative state; the use of persistent caused much confusion as it is descriptive in contrast to permanent, which is prognostic.
- Minimally conscious state, which was later divided into minimally conscious plus or minus, although the distinction was never widely used.
- Minimal Awareness state, minimally responsive state, and similar terms that recognise that many people show behaviours that might be evidence of consciousness.
- Unresponsive wakefulness syndrome and a wakeful unconscious state both developed because the term vegetative can be offensive to some people.
- Coma, which implies an absence of eye-opening and a sleep-wake cycle
- Hyporesponsive, reflex-responsive, and localising responsive states following the gradual return of responses as a person improves
- Transitional vegetative state, inconsistent low awareness state, and consistent low awareness state, a progression that acknowledges variability as a significant component of the person’s state.
- Cortically-mediated state, akinetic mutism, hyperkinetic mutism
- Emergence from a minimally conscious state and post-traumatic confusional state are both terms applied to people considered conscious but still severely impaired.
Several points are evident. The level of consciousness is a continuous variable –a spectrum – and may vary in a patient. Some terms mainly describe responses or behaviours, while others require interpreting the primary data to measure consciousness. Some terms encompass a prognosis, others a neurological basis. A published timeline, available here, shows a few of these terms and the body responsible.
A further recent development is the term cognitive-motor dissociation. This describes the situation when a patient shows no meaningful behaviours, but measures of cerebral function (fMRI or EEG) show responses. At least some of these cases do have evident behavioural reactions. Furthermore, the scientific significance of the findings is not yet agreed upon, and they should not determine clinical decisions.
The term prolonged disorder of consciousness emerged over many years in various guises. It became formally recognised in the 2020 UK National Clinical Guidance on the Management of People with a Prolonged Disorder of Consciousness. It is conveniently abbreviated to PDOC. It is descriptive, not prognostic, and can be used for all patients regardless of age or diagnosis.
PDOC: an introduction.
History explains why so many similar terms are used to describe people now best considered to have a prolonged disorder of consciousness. This section will cover many aspects of the condition. The MindMap below shows the proposed structure; none have been written, but they will be! These pages supplement the National Guideline, which provides much more detail.
The first two pages will particularly interest service managers. They will discuss in more detail what a prolonged disorder of consciousness means, how one judges when someone is no longer unconscious, how many people one expects to see, and the common causes? One surprise to many is that most patients are over 50 years old. Another is that traumatic brain injury is not the most common cause.
The second two pages move to more philosophical matters, considering consciousness and awareness and how one can assess them clinically, even though philosophers and neuroscientists still cannot answer what consciousness is. While you may feel this is unnecessary for a clinician, it is not. You will confront the issues personally. Crucially, the problems will concern families. Having some insights will help you communicate.
The third two pages will be crucial for clinicians who work with patients. They explore neurological damage, how it arises, and why it disrupts awareness. Surprisingly, to some people, the direct information needed to assess awareness is straightforward. However, it depends on your humanity; only another human can evaluate someone’s awareness. Again, contrary to received wisdom, they argue that structured assessments risk misinforming you—any lawyers.
The fourth couplet discusses prognosis and its close association with deciding a person’s best interests. Prognosis is always uncertain, so a vital skill and attribute of a clinician is explaining the limits of certainty and accepting uncertainty—which is usually tiny in contrast to the change needed to affect a decision. Decisions must be made following the Mental Capacity Act of 2005.
The last couple of pages move on to legal and ethical matters. All healthcare staff must practice following the law, so they must understand what it says. The law mainly supports good clinical standards. However, families may dispute clinical decisions, and the best way to handle this is considered. Last, in some instances, existing treatment is stopped, and this process is discussed.
Many pages and posts concern people with a prolonged disorder of consciousness. For example, all pages discussing the Mental Capacity Act will directly affect the management of someone with a prolonged disorder of consciousness.
However, some pages or posts directly consider prolonged disorders of consciousness. The table below lists the relevant posts and pages and will be updated as the site expands.
| Item/link | Title | Comment |
|---|---|---|
| Post-01 | Pain in PDOC | A post, 2021. Initiated by a case of a child ageed two, uncoonscious. Pain entered into the decision-making process. |
| Post-02 | PDOC clinical features. | A post, 2025. Reviewss the clinical phenoomena of people with PDOC. Central feauture is variation within and between patients. |
| Post-03 | Prolonged disorders of consciousness (PDOC) services | A post, 2025. Considers failure of organisations and commissioners to respect the person's rights under the Mental Capacity Act; and how to set up a register and networks to resolve this. |
| Post-04 | Being a Prolonged Disorder of Consciousness (PDOC) expert. | A post, 2025. Reflects on my rrole as an expert and how best to undertake the role, stressing the main focus must be the family. |
| Post-05 | Prolonged disorders of consciousness (PDOC); history and updates. | A post, 2021. Reviews the emergence of the vegetative state, the minimally conscious state, and the prolonged disorderr of consciousness. Consider the change in legal guidance. Focus on three common misunderstandings. |
| Post-06 | Do no harm. | A post, 2021. Stimulated by a PDOC case where no decision was made; the Mental Capactity Act was ignored. Stresses the duty to consider best interests. |
| Post-07 | Challenging clinical decisions. | A post, 2024. Four legal cases which involved challenges. The first, Case A, involved poor decision-making about continuing treeatment in someone in a PDOC. |
| Post-08 | Belieefs, capacity, and best interests. | A post, 2024. Two legal cases, the first involving someone with a PDOC where strong religious beliefs led to dispute about best interests. |
| Post-09 | Holistic best interests in court | A post, 2025. Discusses two cases, YD and PK, and whether legal best interests are entirely holistic, suggesting clinicians take a wider view. |
| Page-01 | PDOC: an introduction and history. | An introductory page in the clinical section, giving a brief history of the terminology. |
| Page-02 | PDOC service design | Considers features of PDOC and of NHS services; concludees one needs a PDOC network centred on a lead service with an outreach service. |
| Page-03 | PDOC: giving a prognosis | Discusses challenges in establishing the prognosis, emphasising its importance and the need for honesty about degrees of uncertainty. |
| Page-04 | PDOC and pain | A page in 2025 summarising a paper that considers whether people with a PDOC can experience feelings of pain. |
| Doc-01 | Table of UK court cases | The is a document with a table of relevant court cases concerning people lacking capacity and what medical treatments they should have. |
| Page-05 | PDOC: emergence | Discusses categorisation of states of unconsciousness, emegence criteria, and "useful consciousness" |
Conclusion
This brief review has raised some of the issues discussed in other pages. It has illustrated how vital law and ethics are and hinted at the relevance of technological investigations, philosophical considerations, such as the nature of consciousness, and linguistic considerations. This broad scope may daunt some people. Alternatively, it provides continuing challenges that can improve your clinical practice with all patients.
