Lecture 11: Consciousness in Clinical Cases

Question 1

What is meant by a disorder of consciousness?

Answer 1

A disorder of consciousness, or impaired consciousness, is a state where consciousness has been affected by damage to brain.

Question 2

Where is the brain damage in disorders of consciousness?

Answer 2

The damage can be very local as well as more global, it can be to subcortical regions or brainstem regions. It can also be to the cortical regions.

It might be at the ARAS (ascending reticular activating system) for example. A set of connected nuclei in the brains that are responsible for regulating wakefulness and sleep- wake transitions. Many neurotransmitters are involved and damage to this area leads to coma or even death.

Question 3

What is the typical procedure when someone first receives brain damage that results in a disorder of consciousness?

Answer 3

Acute brain injury causes coma, and this coma is often temporary. It can sure a few days, or weeks. Then people progress towards one of the several states.

Question 4

What two main types of injury may a patient have?

Answer 4

Non-traumatic brain injury and traumatic brain injury

Question 5

What two main types of non-traumatic brain injury are there?

Answer 5

Anoxic brain injuries: caused by complete lack of oxygen provided to the brain. Results in the death of brain cells after approximately four minutes of oxygen deprivation (e.g. heart attack, drowning).

Hypoxic brain injuries: brain injuries due to a restriction of the oxygen supplied to the brain. Results in the gradual death and impairment of brain cells.

Question 6

Give another name to traumatic brain injury and define it

Answer 6

Also known as an intracranial injury, is an injury to the brain caused by an external force.

Question 7

How is damage caused by traumatic injury often different to that of non-traumatic injury?

Answer 7

All conditions often lead to relatively local brain damage and cell death, contrary to the non-traumatic ones.

Question 8

What typically causes a stroke?

Answer 8

A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or ruptures.

Question 9

What does a tumour refer to?

Answer 9

Tumours relate to abnormal cells form within the brain.

Question 10

Describe typical characteristics of a coma

Answer 10

> A person shows no signs of being awake and no signs of being aware.

> Eyes closed and no response to the environment, voices or pain.

> A coma usually lasts for less than 2 to 4 weeks.

> At some point the person may wake up or progress into a VS or MCS.

> Many types of problems can cause coma (damage to reticular activating system in the brainstem, damage to cortex).

Question 11

WHy may a coma be induced in someone?

Answer 11

“Induced comas” are used to protect the brain during major neurosurgery.

Question 12

Can people in a coma breathe by themselves?

Answer 12

Some comatose patients breathe on their own, others may require a machine to help them breathe.

Question 13

Describe typical characteristics of brain death

Answer 13

Worst outcome would be the person doesn’t survive the coma.

> Total absence of brainstem reflexes.
Flat EEG and an inability to initiate breathing.
PET and other measures such as Doppler ultrasonography show that cortical metabolism and the perfusion of blood to the brain are annihilated.
Once hypothermia (body core temperature below 35) is excluded, and effects of pharmacological/toxic substances, diagnosis of brain death can be established within a day.
Cortical and thalamic neurons quickly degenerate.

Question 14

Describe symptoms of vegetative state/unresponsive wakefulness syndrome

Answer 14

Notes from Victor’s course: sleep wake cycle, breathing, autonomous reactions, eye movements, orienting (sometimes), no reaction or communication. It’s very different than coma because we can see patients make movements or look around. They also have sleep and wake cycles. BUT they don’t respond to outside stimuli, although they have basic reflexes. It is usually followed by coma.

> Wakefulness
No awareness of self or the environment
No sustained, reproducible, purposeful behavioural responses to external stimuli
No language comprehension or expression
Relatively preserved hypothalamic and brain stem autonomic functions
Bowel and bladder incontinence
Variably preserved cranial-nerve and spinal reflexes

Question 15

Describe the characteristics of the minimally conscious state

Answer 15

Wakefulness.
>Fluctuation awareness with reproducible, purposeful behavioral responses to external stimuli.

Minus: Visual pursuit, reaching for objects, orientation to noxious (painful) stimulation and continent behavior.
Plus: Following commands, intentional communication and intelligible verbalisation.

Emergence from minimally conscious state: Functional communication, functional object use.

Question 16

Describe the characteristics of locked in syndrome

Answer 16

This isn’t a disorder of consciousness because the patient is awake and fully aware. Only the body is fully paralysed except for the eyes. Also preserved cognitive abilities.

Typical cause is damage to the brain stem (the pons).

Question 17

What is meant by total locked in syndrome?

Answer 17

Total locked-in syndrome is a version of locked-in syndrome in which the eyes are also paralysed.

Question 18

How does prognosis depend on the brain damage?

Answer 18

Prognosis is worse for non-traumatic injury, so global (like loss of oxygen) than traumatic injury, so local (like head injury).

Question 19

What theory of consciousness can this difference in type of brain damage be linked to? Explain

Answer 19

This can be linked to the global workspace. Global workspace puts together inputs from many areas of the brain. So when there’s damage to only one area, a local damage, the workspace isn’t really affected. However if there is a more global damage to the brain, this will influence so many inputs that come to the global workspace, and interfere more.

Question 20

Comment on the accuracy of diagnosis in disorders of consciousness

Answer 20

One very influential paper showed that some 43% of the patients who have been diagnosed with vegetative state before, actually had minimal consciousness. So a high error rate on diagnoses.

Question 21

What 2 main reasons are there for this high error rate in diagnosis?

Answer 21

1. An inability to move and speak is a frequent outcome of chronic brain injury and does not necessarily imply a lack of awareness. So we can have consciousness but no way of outputting it. The extreme case of it is the locked in syndrome.
2. The behavioural assessment is highly subjective: Behaviours such as smiling and crying are typically reflexive and automatic, but in certain contexts they may be the only means of communication available to a patient and therefore reflect a wilful, volitional act of intention.

Question 22

What diagnosis tools can be used to improve the diagnosis?

Answer 22

Glasgow coma scale

JFK coma recovery scale revised