1: Disorders Of Consciousness Flashcards
What are the four disorders of consciousness
- Locked-In
- Coma
- Persistent vegetative state
- Brainstem death
What is a coma
State of unarousable consciousness
How is a coma defined
E2
V2
M4
What is E2
Eyes open to pain
What is V2
Sounds
What is M4
Flexion (Withdraw) From Pain
What GCS indicates coma and what does this indicates
8 - requires intubation
What are the two broad etiological categories for coma
Neurological
Metabolic
Give 3 neurological causes of coma
Infection (Encephalitis, Meningitis)
Trauma
Seizures: non-convulsive SE
Give 5 metabolic causes of coma
Hypoxia CO poisoning Hypoglycaemia Hypothermia Septicaemia Addison's
Explain self-awareness in coma
No self-awareness
Explain sleep-wake cycle in coma
No sleep-wake
Explain movement in coma
No movement
Define consciousness
Awareness of self and environment, with ability to respond appropriately to stimuli
What are the two aspects of consciousness
- Awareness
- Arousal
What controls arousal
Ascending reticular activating system (RAS) in the brainstem
What controls awareness
Cortex
What causes coma
- Bilateral cortical injury (Awareness)
- Reticular Activating System - RAS Injury (Arousal)
Explain approach to someone in a coma
A-E
Intubate if GCS less than-8
Treat cause
During history of coma, what may slow shallow breathing indicate
Metabolic cause
During history of coma, what may deep rapid breathing mean
Metabolic acidosis
During history of coma, what does rapid shallow breathing indicate
Brainstem lesion
What is decorticate posture
Arms: Flexed
Legs: Extended
What does decorticate posture indicate
Damage to cerebral cortex
What is decerebrate
Arms: Extended
Legs: Extended
What does decerebrate posture indicate
Damage to brain-stem
Define brainstem death
Loss of capacity for consciousness and irreversible lock of capacity to breathe spontaneously
What are three pre-requisites for diagnosing brainstem death
- No endocrine, metabolic, effect depressant drugs or hypothermia causing it
- Known aetiology for reversible damage
- Patient being ventilated
What is step one for diagnosing brain stem death
Ensure dealing with brainstem death, this is either done by:
- History - aetiology supports diagnosis
- If unclear, use EEG
What is step 2 of confirming brainstem death
Exclude reversible cause
How is intoxication excluded
Sufficient period of time since intoxication
How is hypothermia excluded
Core T above 34
How is electrolyte abnormality excluded
Electrolytes in-range
How is acid-base balanced excluded
In-range
How is neuromuscular block excluded
Deep tendon reflexes present
What is step 3 of confirming brainstem death
Formal brain-stem testing
How many steps are there to formally diagnose brainstem death and what are they
6-steps:
- Pupils fixed, non-responsive to light
- Absent corneal reflex
- Caloric test
- No motor response
- No Gag reflex
- Apnoea test
What is the caloric test
50ml ice-cold water injected into the ear - there should be no eye-movements observed (Loss oculovestibular reflex)
Explain motor test
Pain to supra-orbital or limbs
Explain apnea test
- Ensure patient on ventilator has sufficient oxygen so PaCO2 is less than 6kPa
- Gradually reduce RR - causing pCO2 to rise to more than 6.5kPa
- Turn off the ventilator and put patient on 6L oxygen
- Wait 5-minutes to see if patient takes a breathe
- Take ABG. Rise in pCO2 is a positive test as it indicates individual has not breathed
Who can diagnose brainstem death
Two doctors experienced in diagnosing brainstem death with over 5-years postgraduate experience. One must be a consultant. Neither can be attached to transplant team
Legally what are individuals with brainstem death classified as
Legally individual is classified as dead
Define persistent vegetative state
cortex is impaired,, however, brainstem functions are preserved for more than one month
How is persistent vegetative state commonly referred to
awake but not aware
What causes persistent vegetative state
TBI
Diffuse cerebral hypoxia
What are hypoxic causes of PVS
MI
Drowning
Strangled
What usually precedes persistent vegetative state
Coma
Explain sleep-wake cycles in PVS
Present
Explain awareness in PVS
Absent
How is it known individuals with PVS are not aware
- Unable to respond to external stimuli
- Unable to communicate
- Deconjugate eye-movements
Explain reflexes in PVS
Present
What causes PVS
Bilateral diffuse damage to white matter of cerebral cortex. Reticular activating system (RAS) of the brainstem is intact
Explain how damage correlates with presentation in CVS
Cortex = awareness impaired
RAS intact = sleep-wake, reflexes, respiratory control
What is locked-in system
Bilateral damage to ventral pons
What tracts are disrupted in locked-in syndrome
Corticospinal
Corticobulbar
What is only function remaining in locked-in syndrome
Vertical gaze
What region is damaged in locked-in syndrome
Bilateral ventral pons
What are 4 causes of ventral pontine damage
- Ischaemic
- Trauma
- Demyelination
- Tumour
Occlusion of what artery causes ischaemic of ventral PONS
Vertebrobasilar arteries
What haemorrhagic cause leads to damage to ventral pons
Rupture berry aneurysm due to HTN
Describe clinical presentation of locked-in syndrome
- Quadriplegia
- CN Palsy
- Cheyne-Stokes
- Consciousness intact
Why is vertical. but not horizontal eye movement, in tact
Vertical gaze centre is located in midbrain
Horizontal gaze centre is located in PONS
Why is cutaneous sensation intact in locked-in syndrome
Spinothalamic tract runs in dorsal PONS
What investigations are ordered in locked-in
EEG - exclude brainstem death
CT- Identify cause
What two conditions can cause demyelination of the PONS
Multiple Sclerosis
Central pontine myelinolysis
What causes central pontine myelinolysis
Replacement sodium too quickly causing an osmotic demyelination
