23. Persistant vegetative states Flashcards
Define consciousness
State of awareness of the self and one’s relationship to the environment
What are the different components making up consciousness?
Arousal - sleep/wake cycle
And the total sum of our interactions with the environment
What is ‘locked-in syndrome’?
This is a state of full body paralysis but the patient is still conscious
There is complete paralysis of the voluntary muscles (sometimes but often apart from the eyes) so the patient cannot move or communicate but they are aware and cognitively functioning
Often occurs due to a lesion in the region of the pons
What is the Glasgow coma scale and what is it used for?
Neurological scale to give a reliable and objective way to record the conscious state of an individual
It is used to asses the level of consciousness by first responders, nurses, doctors and also in intensive care
Records the level of eye, verbal and motor responses
Which region of the brain is responsible for consciousness?
There are a group of neurones in the core of the brainstem i.e. in the midbrain and pons and these are responsible for consciousness - damage to these will result in the patient going into a chronic coma and they will never wake up
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Where do these neurones project to?
These project to variable regions within the brain - subthalamus, hypothalamus, thalamus, basal forebrain
What neurotransmitters do these neurones use?
These neurones are heterotropic i.e. they use different neurotransmitters
They may be cholinergic, noradrenergic and orexinergic
What is meant by ‘wakefulness’?
This is the most basic form of consciousness - if you are wakeful and aware, then you are conscious
What is the vegetative state?
This is a complex neurological condition in which the patient appears to be awake but shows no signs of awareness of themselves or their environment
Describe the state of a vegetative patient
These patients have full arousal but they do not have any wakefulness
SO their eyes can be open and they look like they are awake but they are not aware of their surroundings and no not interact - there are no small or minimal motor movements
What is the minimal consciousness state?
This is a level of wakefulness accompanied by inconsistent but reproducible signs of awareness
Describe the state of a patient in a minimal consciousness state
These patients will have some degree of awareness - will have a slight response to sensory stimulus e.g. may be able to move their hand, smile, cry, mumble etc
The most common motor movement in these patients is eye tracking - tracking people that are in the room
What is akinetic mutism and how does it occur?
This is where there is damage to the cingulate gyrus in the frontal lobe i.e. the white matter
In this case, people lack the motivation to respond to anything - can talk or move normally if it is imperative but otherwise lack the motivation to do so
Describe the progression from a coma to a permanent vegetative state
Coma - temporary state of unconsciousness lasting for 2/3 weeks
Vegetative state - if have been in a coma for longer than 2/3 weeks
Persistent vegetative state - if been in a vegetative state for more than a month
Permanent vegetative state - if been in a persistent vegetative state for more than 6 months (or 12 months if suffered major trauma)
What is the significance of being in a permanent vegetative state?
In this instance, it is very unlikely that the patient will recover from this state especially the longer that they have been in this state for
What is the cause for vegetative states?
There are a wide range of causes
Generally this occurs due to some form of trauma but may also occur due to a level of chronic neurodegeneration
Give the anatomical structures in which damage could result in a patient being in a vegetative state
Medial prefrontal cortex
Thalamus (especially central thalamus)
Inferior parietal lobe (especially where it meets the temporal lobe)
Basal ganglia
How is the vegetative state diagnosed?
History
Imaging
Electrophysiology (lesser degree)
Use examinations to assess all of the senses - visual, olfactory, auditory, tactile or noxious
To also get a sense of the their comprehension of language or expression
What is the diagnostic criteria for a vegetative state?
Cycles of eye opening and closing giving the appearance of a sleep wake cycle
Complete lack of self or environment
Complete or partial preservation of hypothalamic and brainstem autonomic functions
What types of imaging is used to assess a vegetative state?
Electophysiology
MRI
How is electrophysiology used to asses a vegetative state?
EEG - electrodes on head, measure the electrical activity of the brain
Event related potentials (ERP) - put headphones onto the patient, they listen to sounds and you look for responses from the patient
How is MRI used to asses a vegetative state?
MRI used for anatomical imaging to look at any abnormal calcifications or neuronal swellings/extracellular swellings
OR used for functional imaging - can see which area of the brain is activated in particular as the metabolism increases
What are the different factors that can affect the recovery of a patient in a vegetative state?
Time spent in this state - the longer you spend in this state, the less likely you are to recover
Age - younger patients are more likely to recover as they have a much greater level of neuronal plasticity
The type of brain injury that has occurred - hypoxic brain injuries do not tend to do well
