Lec 48 Disorders of Consciousness Flashcards
What is arousal vs awareness?
arousal = level of consciousness – are the lights on
awareness = content of consciousness – is anyone home
What structures mediate arousal?
ascending reticular activating system (ARAS) [in ponto-mesencephalic junction]
thalamus
thalamo-cortical relays
What happens to level of arousal and EEG if you transect the medulla? midbrain?
medulla = normal midbrain = loss of arousal, desynchronized EEG
Where are the source nuclei of the ARAS located? their NT?
nuclei in ponto-mesencephalic junction
NT = ACh
What structures mediate awareness?
cerebral cortex
What are the 6 states of conciousness?
Awake = full wakefulness
Drowsy = able to stimulate full arousal by non-noxious stimuli [saying their name]
lethargic = responds to non-noxious stimuli but unable to be brought to full arousal [say name]
obtunded = respond to non-noxious stimuli but more depressed level of consciousness
stuporous = noxious stimuli needed to raise level of arousal
coma = unresponsive to all stimuli
What is the glasgow coma scale?
to asses arousal
assess eye opening, verbal responsivity, and motor responsitivity
score from 3 to 15 with 15 = fully awake 3 = coma or death
What 3 principal features used to localize source of arousal dysfunction?
- respiratory pattern
- eye function
- motor responsitivity
“when you don’t know the where and whys, listen to breathing and look at the eyes”
Match the type of respiratory pattern with the location of dysfunction
- diffuse forebrain dysfunction
- midbrain injury
- rostral pons
- caudal pons
- medulla
A. ataxia B. apneusis C. hyperventilation D. respiratory arrest E. Cheyne-Stokes respiration
- diffuse forebrain dysfunction
- – E. Cheyne Stokes respiration [crescendo then decrescendo pattern] - midbrain injury
- – C. hyperventilation - rostral pons
- – B. apneusis [extended periods of apnea] - caudal pons
- – A. ataxia [disorganized arrhythmic pattern] - medulla
- - D. respiratory arrest
What happens to the eyes in a thalamic lesion?
small, reactive, symmetric pupils
What happens to the eyes in a pretectal lesion?
fixed, dilated pupils
What happens to the eyes in a pontine lesion?
pinpoint pupils
What happens to the eyes in a midbrain lesion?
fixed, mid size pupils
What happens to the eyes in a herniation lesion?
- 1 fixed, dilated pupil
suggests mass effect = emergency
What are afferent and efferent of corneal reflex?
afferent = V1 branch of CN V [CN V main nucleus in pons]
efferent = CN VII to orbicularis oculi [CN 7 nucleus in pon]
What should you think if you see one fixed dilated pupil?
herniation! it might be an emergency
What happens if you inject cold water into right ear canal?
eyes both turn to right with nystagmus to left
What happens if you inject warm water into right ear canal?
eyes both move to left side with nystagmus to the right
What happens if you have a lateral pontine lesion? to VOR function? when cold water injected in ipsilateral or contralateral side?
PPRF on side of lesion can’t function –> VOR not intact when head turned to contralateral side
ie. left lateral pons lesion. eyes do not move when head turned right
cold water in ipsilateral: no horizontal eye move
cold water in contralateral: normal eye move
If you have a cortex lesion will you have VOR?
yes! –> you will have VOR but you won’t be able to control it
[in normal you have dolls eyes but can override it if you want to look in the direction of head turn. if no cortex can’t override so always have dolls eyes]
If you have no cortex or brainstem will you have dolls eyes reflex?
nope!
What happens if you have a bilateral midbrain lesion? to VOR function? when cold water injected in ipsilateral or contralateral side?
bilateral CN 3 nuclei can’t function so can’t use medial rectus to adduct
If you have a right lateral pontine lesion what happens if:
- turn head to right
- turn head to left
- cold water into right ear
- cold water into left ear
- turn head to right –> both eyes shift left
- turn head to left –> eyes don’t move
- cold water into right ear –> eyes don’t move
- cold water into left ear –> eyes drift left
If you have a bilateral midbrain lesion what happens if:
- turn head to right
- turn head to left
- tilt head back or forward
- cold water into right ear
- cold water into left ear
- turn head to right –> left eye goes, right eye doesn’t move
- turn head to left –> right eye goes, left eye doesn’t move
- tilt head back or forward: eyes do not move
- cold water into right ear –> right eye to right, left eye doesn’t move
- cold water into left ear –> left eye to left, right eye doesn’t move
symptoms are bc CN 3 nucleus disrupted and vertical movements regulated also in midbrain
What happens to motor responsitivity in large cortical lesion?
lack of contralateral purposeful movement
What happens to motor responsitivity in upper midbrain lesion?
decorticate/flexion posturing = abnormal stiff posturing with bent arms, clenched fists, legs out straight, arms bent in toward body and wrists and fingers bent and held on chest, can be unilateral or bilateral
What happens to motor responsitivity in upper pontine damage?
decerebrate/extensor posturing = abnormal body posture w/ arms and legs straight out, toes pointed down, head and neck arched back, muscles held rigidly, can be unilateral or biltaeral
What causes locked-in syndrome? clinical features?
cause: structural/functional brainstem transection just below mid-pons. ARAS above mid-pons = intact so preserved consciousness but disruption efferent paths
clinical: conscious, mute, quadriplegic, no conjugate lateral eye movements, preserved midbrain mediate movements (voluntary opening, vertical movement, convergence)
Is there arousal in vegetative state? awareness?
arousal = variable, can be full awareness = none
How does minimally conscious state differ from vegetative?
both can have variable or full arousal
vegetative = no awareness; minimally conscious has partial/variable awareness
What are characteristics of coma?
- complete awareness failure
- complete arousal failure
- eyes closed
What are characteristics of vegetative state?
preserved capacity for arousal (spontaneous or stimulation induced)
sleep wake cycle
no awareness
What are characteristics of minimally conscious state?
- preserved arousal and partial awareness
- see eye movements (tracking, stimulus fixation), ability to follow simple commands, and purposeful behavior
What does brain death mean? signs?
no evidence of brain stem function
– absent midbrain reflexes = no pupillary reactivity
- absent pontine reflexes = no VOR or corneal reflex
- absent medullary reflexes = apnea
