Gill-Thwaites & Elliott Consultants Ltd


Prolonged Disorders of Consciousness (PDOC) is a collective term for a spectrum of conditions where the individual has no or very limited levels of awareness. PDOCs are caused by severe damage to the brain through trauma such as a road traffic accident or non-traumatic injury, for example, anaesthetic accident, heart attack or asthma attack. There are three key diagnoses that would be considered:

Prolonged Disorders Of Consciousness (PDOC)

Individuals with PDOC are those who remain in a state of wakefulness but absent or reduced awareness (i.e. vegetative or minimally conscious state) for more than 4 weeks. A state of VS or MCS lasting for more than 4 weeks post-injury is classified as “continuing” VS/MCS. “Chronic” VS/MCS, which can only be confirmed through appropriate specialist assessment, occurs if this state persists for more than 9 months for anoxic or other metabolic brain injury or more than 18 months for traumatic brain injury. Permanent VS or MCS can only be confirmed when there have been no further changes in trajectory for 6 months (as measured by serial standardised PDOC assessment).


Coma is a state of complete unawareness, which occurs in the acute stages of brain trauma. It will usually last for no more than six weeks, by which time there will be either signs of emerging awareness towards recovery or a continued state of unawareness such as VS.

Vegetative State

An individual in VS will have no awareness of themselves or the environment around them.

However, VS is quite different from coma as the individual will often have spontaneous movements, some of which may form quite complex patterns; the eyes are open and may move and there may be evidence of moaning or grunting. To a casual observer, the individual can appear to be aware although profoundly disabled, but the key to all of these behaviours is that they are inconsistent and are unconnected to any meaningful interaction (Giacino 2001). The features are present as a result of impairment of the brain stem and cerebral cortex, but with an intact arousal mechanism hence the apparent sleep–wake pattern (Jennett 1993).

An individual in VS has no evidence of awareness at any time, no meaningful response to visual, auditory, tactile or noxious stimuli, and no evidence of comprehension of language or meaningful expression.

Diagnosis of Vegetative State

At present, there is no medical test available to diagnose VS. Therefore, clinical diagnosis must be established from observation of behaviour, compatible with the clinical features of the diagnosis, to ascertain the individual’s awareness of self and the environment, and potential for communication (Royal College of Physicians 2020). Misdiagnosis has been identified in a number of studies at a rate of up to 43% of cases reviewed. It is, therefore, suggested that thorough, standardised assessments are completed by expert assessors in this field.

Treatment of Individuals in Vegetative State

There is some evidence that those individuals in VS have a chance of recovery in the early stages. It is, therefore, important that the individual should be maintained in the best physical state, which will prevent secondary complications (Jennett 1997). Andrews (1999) specified that prerequisites of assessment are for the patient to be medically stable, to have sound nutritional status, controlled posture, and minimised complications due to neurological imbalance.

Physical management procedures are used to maximise motor functioning, prevent contractures, and promote the optimum position to prevent masking of functional ability. Sensory programmes are used to regulate stimulation and provide opportunity for the individual to respond.

Once the individual is diagnosed as being in a permanent VS (six months following non-traumatic injury and 12 months following traumatic injury), the treatment options are reduced and will generally convert to creating a programme of care that is more palliative than rehabilitative, focusing on symptom control and management. However, it should be recognised that later changes in this condition have been documented and so it is recommended that a regular review and assessment of the diagnosis are carried out within the long-term setting.

Minimally Conscious State Minus

Bruno et al (2012) further characterised MCS-, at the lower end of the MCS spectrum as demonstrating:

Minimally Conscious State Plus

These individuals show, in addition, some evidence of language processing/communication such as following simple commands, intelligible verbalisation or intentional communication albeit inconsistently.

Minimally Conscious State

MCS has developed as a syndrome in its own right following a greater understanding of the parameters of consciousness of the VS patient. The improved understanding of VS enabled clinicians to identify a group of patients who were outside the clinical definition of VS but were displaying signs that could neither be described as VS nor fully conscious. MCS is defined as:

“…a condition of severely altered consciousness in which the person demonstrates minimal but definite behavioural evidence of self or environmental awareness.” (Giacino et al 1997)

The nationally recognised clinical features of MCS, of which just one needs to be present within an individual, are:

MCS can be a transient state from VS to fully conscious or can become permanent (Jennett 2002). There is, as yet, no certainty that can be provided to the individual or their family, as to the future course of their condition on this continuum of Prolonged Disorders of Consciousness.

Diagnosis of Minimally Conscious State

As with VS, the diagnosis of MCS is reliant on careful assessment of observable behaviours. In order to be diagnosed in MCS, a standardised assessment such as SMART is used to establish whether there is reliable and consistent evidence of either interactive communication or functional use of objects. Due to the nature of this condition, it is important that the assessment is conducted by experienced assessors to enable the individual to respond, in whichever way possible, and that it is carried out over time in order to capture consistent patterns of behaviour.

Intervention for an Individual in Minimally Conscious State

Once a diagnosis is reached, the optimum conditions for responding are established within the individual’s environment. A structured programme, which will increase the quality and consistency of responses and so enable greater communication and interaction with the environment, is the primary focus to increase the functional ability of the individual.

Emergence From Minimally Conscious State

Emergence from MCS is signalled by the recovery of reliable and consistent responses. The RCP 2020 defined the operational parameters as follows:
Functional use of objects: Intelligent use of at least two different objects on two consecutive evaluations (with or without instructions) e.g. writes or draws.
Consistent discriminatory choice making. Consistently indicates the correct choice from two pictures on 6/6 trials on two consecutive occasions (use at least three different picture pairs).

Functional Interactive Communication

Evidence of awareness of self: Gives correct yes/no responses to 6/6 autobiographical questions on two consecutive evaluations.
Evidence of awareness of self: Gives correct yes/no responses to 6/6 basic situational questions on two consecutive evaluations.


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Bruno, M.A., Majerus. S., Boly, M., et al. Functional neuroanatomy underlying the clinical subcategorization of minimally conscious state patients.

J Neurol 2021; Jun: 259(6): 1087-98.

Giacino, J.T., Zasler, N.D., Katz, D.I., Kelly, J.P., Rosenberg, J.H. and Filley, C.M. (1997) Development of practice guidelines for assessment and management of the vegetative and minimally conscious states.

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Cambridge: Cambridge University Press.

Royal College of Physicians (2020) Prolonged disorders of consciousness following sudden onset brain injury, National clinical guidelines.

London: Royal College of Physicians Publications.