Following severe brain injury patients may progress through stages of coma, vegetative state and minimally conscious state and eventually emerge into a state of awareness. Some, however, remain in a vegetative state or minimally conscious state for a prolonged period or for the rest of their life.
The vegetative state is a term which describes a situation where there is no evidence of:
- Awareness of self or interaction with others.
- Sustained purposeful or voluntary behaviours either spontaneously or in response to stimuli.
- Language, comprehension or meaningful communication.
The following clinical features are usually present:
- Eye opening and closing cycles (as in a sleep-wake cycle).
- Spontaneous respiration and circulation.
The minimally conscious state is a term which is applied when there is very limited but clear evidence that the person has some awareness of self or their environment. They exhibit inconsistent but reproducible behaviours including:
- Episodes of crying/smiling in response to speech or visual stimuli of an emotional nature.
- Vocalisation or gesture in response to speech.
- Touching or holding objects.
- Eye movement following a stimulus.
As a person emerges from the minimally conscious state their responses become more consistent and reproducible, they begin to show functional interactive communication or use of objects.
Locked-in syndrome is a rare disorder distinct from but occasionally confused with prolonged disorders of consciousness. In this condition damage to the front (anterior) part of the brainstem disrupts control of voluntary movement but the arousal system and brain remain intact. The patient is both aware and awake but cannot speak or move their limbs. They may be able to communicate with limited eye movements only. It is described by the journalist Jean-Dominique Bauby in “The Diving Bell and the Butterfly”.