Consciousness (Lecture 19) Flashcards
4 major components of brainstem
cranial nerve nuclei & related structures
long tracts
cerebellar circuitry
reticular formation and related structures
long tracts
dorsal column medial lemniscal pathway
lateral corticospinal tract
spinothalamic
clinical consequences of damage to CN nuclei and related structures
cranial nerve abnormalities
clinical consequences of damage to long tracts
hemiparesis and/or hemianesthesia
clinical consequences of damage to cerebellar circuitry
ataxia
clinical consequences of damage to reticular formation and related structures
impaired level of consciousness
impairment in autonomic functions (BP, HR)
what is the reticular formation
core of cell bodies loosely grouped into nuclei that run throughout the entire length of the brainstem tegmentum (above the basis)
function of reticular formation
rostral 1/2: maintenance of alert, consciousl state in the cerebrum
caudal 1/2: autonomic reflexes (HR, BP, respiration, digestion), motor (origin of reticulospinal tract), reflexes involving the head (coughing, sneezing, swallowing, sucking, etc)
where is rostral 1/2 of reticular formation found
midbrain and rostral pons
where caudal 1/2 of reticular formation found
caudal pons and medulla; continuous with grey matter of spinal cord
purpose of reticular activating system
sends info from pontomesencephalic reticular formation to the thalamus and finally the cerebral cortex
requirements of consciousness
alertness (RAS)
attention (RAS, limbic system, frontal & parietal lobes)
awareness of surroundings (primary sensory cortices and sensory association cortex)
Coma
unarousable unresponsiveness
- pt lies with eyes closed
- brainstem reflexes still present
- no sleep wake cycles
brainstem reflexes
blink to threat pupillary light response oculocephalic reflex corneal reflex gag reflex
how to test blink to threat (CN II, VII)
hold eyes open and come toward pt with hand. both eyes should blink
how to test pupillary light response (CN II, III)
shine light in eye, pupil constricts
how to test oculocephalic reflex (CN VIII, III, VI)
hold eyes open, turn head to left, eyes should move right
how to test corneal reflex (CN V, VII)
touch cornea with wisp of cotton, both eyes should blink
how to test gag reflex (CN IX, X)
touch back of throat with tongue depressor, pt should gag
continuum between consciousness and coma
awake and alert drowsy stuporous comatose brain death
glasgow coma scale
helps determine progonsis in TBI, measures level of consciousness
highest possible score on glasgow coma scale
15
worst possible score on glasgow coma scale
3
what score on the glasgow coma scale indicates a good prognosis
8 or higher
bilateral damage to these structures leads to a permanent comatose state
cerebral hemispheres
medial aspect of thalami bilaterally
reticular formation of the pons and midbrain
how to perform neurologic exam with someone with decreased level of consciousness
cranial nerve reflexes
observe for motor activity
reflexes
response to pain (sternal rub, nail bed pressure)
decorticate posture
LE extended, UE flexed
rubrospinal tract
decerebrate posture
UE and LE ext
reticulospinal tract/vestibulospinal tract
most common general cause of decreased level of consciousness
bilateral cerebral hemisphere dysfunction (due to trauma or toxic/metabolic causes)
what can cause bilateral cerebral hemisphere dysfunction
medications illicit drugs liver failure kidney failure hypoxia trauma
why do pts with a decreased LOC often require an imaging study of the brain
determine if there is anything that can be fixed
Which of the following are present in brain death? purposeful response to stimuli sleep-wake cycles cranial nerve reflexes cortical electrical activity cortical blood flow
purposeful response to stimuli- no sleep-wake cycles- no cranial nerve reflexes- no cortical electrical activity- no cortical blood flow- no
Which of the following are present in coma purposeful response to stimuli sleep-wake cycles cranial nerve reflexes cortical electrical activity cortical blood flow
purposeful response to stimuli- no sleep-wake cycles- no cranial nerve reflexes- yes cortical electrical activity-abnormal cortical blood flow-yes
Which of the following are present in persistent vegetative state? purposeful response to stimuli sleep-wake cycles cranial nerve reflexes cortical electrical activity cortical blood flow
purposeful response to stimuli- no sleep-wake cycles- yes cranial nerve reflexes- yes cortical electrical activity- yes cortical blood flow- yes
Which of the following are present in minimally conscious state purposeful response to stimuli sleep-wake cycles cranial nerve reflexes cortical electrical activity cortical blood flow
purposeful response to stimuli- inconsistent sleep-wake cycles- yes cranial nerve reflexes- some cortical electrical activity- yes cortical blood flow- yes
criteria for brain death
no purposeful response to painful stimuli no CN reflexed no spontaneous respirations no reversible cause for coma EEG or angiogram 2 separate exams required
difference between persistent vegetative state and minimally conscious state
they are the same except minimally conscious state my intermittently and inconsistently perform any of the following:
- visual tracking
- follow simple commands
- signal yes/no
- intelligible verbalizations
- restricted purposeful behavior
what causes locked-in syndrome
bilateral damage to basis of pons (typically bilateral infarct)
symptoms of brain ischemia
- face motor/sensory loss on one side and body motor/sensory loss on the other side
- eye movement abnormalities
- pupillary abnormalities
- nystagmus
lateral medullary syndrome caused by
PICA thrombosis
