Arousal Coma And Unconsciousness Flashcards
Define arousal
State of wakefulness - self aware and can communicate
Define consciousness
Arousal and content
Awareness of both self and the external environment determined by a motor response to internal or external stimuli
Define coma
Total absence of awareness of both self and the external environment
Severest impairment of arousal is the inability to
- obey commands
- speak
- open eyes to pain
GCS 3-8
Sleep like but cannot be roused
What is the lowest GCS
3
What are the three parameters assessed in the GCS
Eye opening
Best verbal response
Best motor response
Eye opening types and equate to what number
Spontaneous 4
To speech 3
To pain 2
Non 1
Best verbal response types and number
Orientated 5 Confused 4 inappropriate 3 Incomprehensible sounds 2 None 1
Best motor response and number
Obeys commands 6 Localised pain 5 Flexion to pain 4 Flexion abnormal 3 Extension 2 None 1
What does consciousness depend on
Functioning reticular activating system in Thalamus - works as a relay station - connects to cortex without is in for cannot come in and out the brain
Functioning cortex -brain not damaged
Arousal and awareness require …
… an intact reticular activating system
Cognition and consciousness require …
… intact cerebral cortex
What is the main component of the ascending reticular activating system
Tegmental tract
Receives - info from the surrounding neural tissue
Conveys - impulses through multineuronal, polysynaptic pathways to hypothalamus and thalamus and thence to the cerebral cortex
Altered states of consciousness - acute
- clouding of consciousness - attention lack, slow thinking, confusion, memory loss, drowsiness - alcohol
- delirium - as above + disorientation and hallucinations
- stupor- sleep like state, rousable with vigorous stimulation unlike a coma
Can be caused by drugs or lack of oxygen
Altered states of consciousness - chronic
Dementia - mental function, memory, comprehension and speech
Hypersomnia - excesssive drowsiness intermittent wakeming
Vegetative state - after severe brain injury awake but no evidence of conscious intelligence
Causes of a coma
Lesions causing diffuse brain dysfunction
Supratentorial mass lesions causing brain stem compression- cerebral
Infratentorial lesions causing brain stem compression - cerebellar and brain stem
Intrinsic lesions of the brain stem itself
Psychiatric states that may mimic comatose states - drugs
How do you know the conscious state of the lesion causing coma ?
- pupillary signs
- oculicephalic and oculovestibular signs
- motor response to painful stimulus
- respiratory system
Pupil size and reaction contorted by
PS pupillary constrictor - runs with the occulomotor nerve from the EW nucleus innervate ciliary constructed causes the pupil to constrict
S pupillary dilator - nerve arise from the post sympathetic nerves arising from the superior cervical ganglion
Parasympathetic pathway
Retina -> optic N -> optic tract -> lateral geniculate nucleus -> 90% to occipital cortex -> 10% to EW nuclei -> PS Pre G with III -> ciliary ganglion -> PS post G -> short ciliary nerve -> constrictor muscle -> constrict
Sympathetic pathway
Hypothalamus -> via brainstem and cervical spinal cord -> thoracic 1 -> via ventral roots and sympathetic chain -> Sup Cervial Gang -> via carotid artery and cranial cavity -> III -> levator palp superioris + nasocilary/ciliary G BV of eye and nasociliary and long ciliary pupil
What are the metabolic causes of fixed dilated pupils
Anoxic encephalopathy
Anticholinergics - atropine
Botulism
Oculocephalic reflex
Conscious - eyes move with head
Unconscious - rotate head to one side and eyes remain in original position and slowly relate to mid position
Oculovestibular reflex -
Head to 30 degrees
Cold water in ear - normal: slow deviation to side and then fast opposite
Comatose: patient tonic deviation to cooled side
No reaction indicates severely damaged brain stem
Metabolic coma can show normal or depresses
Other patterns associated with damage
Motor reflexes
Abnormal patterns of breathing
Automatic breathing
Causes of coma
Diffuse brain dysfunction
Supratentorial lesion
Uncal / tentorial herniation
Subtentorial lesions
