Disorders of Consciousness

Question 1

What are the two main components of consciousness?

Answer 1

Wakefulness and awareness

Question 2

Draw the graph of states of consciousness with just wakefulness and awareness

Answer 2

Wakefulness vs awareness
Low w low a = Coma, general anaesthesia
High w low a = Vegetative state, epilepsy
High w middle a = minimally conscious state
Middle w middle a = sleep
High w high a = wakeful conscious and locked-in syndrome

Question 3

Define a vegetative state

Answer 3

Awake but not aware

Question 4

What are the 3 axes of consciousness?

Answer 4

Awareness
Wakefulness
Behaviour

Question 5

How can you use fMRI in minimally conscious patients? What is the problem with this?

Answer 5

fMRI - make actions into codes for yes and no
Say patients imagining different actions activates the same brain activation as healthy volunteers
Can answer questions correctly
Patients have woken up and said they are doing the task
Some patients struggle to carry out two levels of cognition - e.g. deciding if an answer is yes or no, then doing the imagining

Question 6

What movement differentiates minimally conscious patients from vegetative patients?

Answer 6

Non-reflex movements ie smooth pursuit

Question 7

What differentiates coma and vegetative state?

Answer 7

Physiologically little difference (both 40-50% of normal waking cerebral metabolism)
Consciousness

Question 8

How does recovery from vegetative state affect metabolic rate?

Answer 8

Very little increase - nowhere near back to normal (still around 40-50%)

Question 9

What is the effect of thalamic stimulation on a minimally conscious patient?

Answer 9

If stim can begin to
1. Fixate on object A when asked what is object A
More stim
2. After a few days can name object
Improves intelligible and non-intelligible responses. Reduces proportion with no response.

Question 10

What is an EEG?

Answer 10

Electroencephalogram
Non-invasive - electrodes placed on scalp
Measures voltage fluctuations resulting from ionic current within the neurons of the brain.

Question 11

How can you use an EEG? What can you use it for?

Answer 11

Create a matrix of the delta slow waves to the alpha higher frequency waves. Use graph theory to make a graph. Hubs formed which relate to different actions e.g. speech. Looking for shortest routes from one hub to another. Good way to measure between non-informative blood flow and informative use of questions. A lot of patients that later recover captured by this method but not by the question method.
Identifies patients with a low cerebral blood flow but who still create complex cerebral interactions.

Question 12

What is TMS? How can you use it when looking at sleep?

Answer 12

Transcranial magnetic stimulation
Coin creates a pulse of magnetic change. Creates a pulse of electrical current due to electrical activity in the brain. Measures waves spreading from right premotor cortex.
During wakefulness, cortical dynamics are complex and re-entrant. In slow wave sleep, you get a slow wave of perturbation.

Question 13

What does ERP stand for?

Answer 13

Event related potential

Question 14

List the different brain measures

Answer 14

EEG - direct and portable

EEG Evoked ERP-TF - uses connectivity signatures which are easy to calculate and informative