Neuro - Disorders of Conciousness

Question 1

What are the main disorders of consciousness and how can they be distinguished?

Answer 1

Consciousness has two main components: wakefulness and awareness
Coma: (absent wakefulness and absent awareness)
- lasting >6 hours
- cannot be woken
- doesn’t respond to painful stimuli
- lacks normal sleep-wake cycle
- does not initiate voluntary actions

Vegetative state: (wakefulness but absent awareness)
- severe cortical damage with preservation of brainstem function
- preserved capacity for external stimulus to influence arousal: retain sleep-wake cycle, range of spontaneous behaviours
- absence of environmental awareness or awareness of self

Minimally conscious state: (wakeful and minimal awareness)- severely altered consciousness in which some evidence of environmental or self awareness exists-
- must have reproducible responses which are not solely reflex arc movements.

Locked-in syndrome: (preserved wakefulness and awareness, BUT paralysis)These states are not necessarily fixed.

Question 2

What are the causes of disordered consciousness?

Answer 2

1. Traumatic- axonal injury- bleed- vasospasm
2. Vascular- stroke (basilar infarct)- SAH
3. Infective- encephalitis- abscess- sepsis
4. Metabolic- hypo/hyperglycaemia- hyponatraemia- hepatic encephalopathy- uremic encephalopathy- hypothermia
5. Hypoxia- cardiac arrest- respiratory failure- drowning
6. Drugs- anaesthetic agents- benzodiazepines- alcohol

Question 3

How can you prognosticate after disordered consciousness and brain injury?What factors indicate a potentially favourable prognosis?

Answer 3

ERC and ESICM recommend that multiple predictors should be used to prognosticate and that prognostication should take place after a period of 72 hours of stability and optimisation.
Days 1-2:
- Controlled temperature 32-36 for at least 24hrs (avoidance of pyrexia for 72hrs)
- rewarming

After 72hrs:
- check motor score of GCS
- M<4 plus:- at least 2 of:
- absent pupil or corneal reflexes
- bilaterally absent N20 SSEPs
- highly malignant EEG (burst suppression, unreactive, status) - elevate NSE
- status myoclonus <72h - anoxic injury on CT/MRI…indicates poor prognosisA potentially favourable prognosis:- young age- traumatic aetiology- short duration of impaired consciousness