Coma Flashcards
Define Coma
A state of unrousable unconsciousness
Define arousal
Level of consciousness/alertness
- the function of reticular activating system in pons and midbrain and its interaction with the thalamus
Define awareness
Content of counsciousness
- awareness of self environment
- function of multiple cortical areas
What are the four general causes of coma?
Massive cortical damage
Brainstem lesion
Brainstem compression
Diffuse physiological brain dysfunction
What is massive cortical damage?
Extensive damage to the brain cerebral cortex and cortical connections
- unilateral
- bilateral
What are the causes of unilateral cortical damage?
Large expanding mass lesions which causes increased ICP
e.g. haemorrhage, large middle cerebral artery infarct
What are the causes of bilateral cortical damage?
Subarachnoid haemorrhage Encephalitis Diffuse brain injury Acute hydrocephalus Diffuse cerebral oedema Hypoxic-ischaemic encephalopathy
What is a brainstem lesion?
A structural injury to the brainstem or thalamus, e.g.
- bilateral thalamic lesions
- ischaemia
- tumour
- haemorrhage
- stroke
What is a brainstem compression?
A supratentorial mass lesion within the brain compresses the brainstem inhibiting the ascending reticular activating system
e.g. coning from a brain tumour or haemorrhage
What is diffuse physiological brain dysfunction?
Generalised severe metabolic/toxic disorders depress cortical and ARAS function, e.g.
- Hypothermia
- Sudden hypertension
- Prolonged status epilepticus
- Drugs, toxins, poisonings
- Psychiatric
- Metabolic = derranged Na, raised Ca, derranged glucose, renal failure, hepatic failure
- Endocrine = hypothyroidism, Addison’s, Pan-hypopituitarism
What are the most common causes of coma?
Metabolic disorders (35%)
Drugs and toxins (25%)
Mass lesions (20%)
Name two important coma mimicks
Locked in syndrome
Psychogenic coma
What is locked in syndrome?
De-efferented motor tracts, leads to:
Complete paralysis except blinking and vertical eye movements intact in ventral pontine infarction
Awareness and arousal retained
Describe the immediate management of coma
ABC
- intubate if necessary
- improve oxygen sats and correct BP
- warm up/cool down
Blood glucose if hypoglycaemic
Treat seizures with buccal medazolam
IV Abx if fever and meningism
Antidote if OD, or thiamine if Wernicke’s encephalopathy
Treat underlying cause
When is the neurological assessment of a coma patient not reliable?
If they:
- are metabolically derranged
- are hypothermic
- have sedative drugs in their circulation
- have an endocrine disturbance
What four specific things are involved in the neurological examination?
Meningism signs
Fundi
Brainstem function
- pupils; eye movements and position; other reflexes;
Lateralising signs
What does a dilatation of one fixed pupil mean?
Compression of CN III - surgical emergency
What does bilateral mid-point reactive pupils (normal) mean in coma?
Sedative drugs that are not opiates
What does bilateral light-fixed dilated pupils mean?
Sign of brain death
- occur in deep coma of any cause, particularly:
> barbiturate intoxication
> hypothermia
What does bilateral pinpoint, light-fixed pupils mean?
Pontine lesions (e.g. haemorrhage), or Opiates
What are dysconjugate eyes and what are they a sign of?
Divergent ocular axes
- e.g. skew deviation (one eye up, one eye down)
Sign of Brainstem lesion
What is conjugate daze deviation a sign of?
Towards the lesion in frontal lobe and the normal limbs
=> intact side pushing eyes away
Away from lesion in brainstem towards weak limbs
=> PPRF in pons controls lateral gaze ipsilaterally
What is the oculocephalic response (vestibulo-ocular reflex)?
Normally, passive head turning produces conjugate ocular deviation away from direction of rotation
Dissapears in: deep coma, brainstem lesions, brain death
What other brainstem reflexes can be tested?
Corneal reflex
Cough/gag reflex
Respiratory drive - hypercapnia
What lateralising signs can be looked out for?
Asymmetry of response to visual threat
Asymmetry of face
Asymmetry of tone
Asymmetry of decerbrate and decorticate posturing
Asymmetrical response to painful stimuli
Asymmetry of tendon reflexes and plantar response
Which form of imaging is best at revealing a midbrain/brainstem lesion, white matter disease or encephalitis?
MR
Which form of imaging is best at detecting a basillar artery thrombosis?
MR angiogram or CT angiogram
What is CT scan good at?
Quick and easy, will reveal blod or large hemisphere lesion
When is a Lumbar puncture indicated in coma?
When imaging is normal and no cause for coma
What are the outcomes of Coma?
Regain Consciousness
- Minimally conscious
- Dependant
- Good recovery
Persistent Vegatative State
Death
