Flashcards in Quiz 1 - definitions, substrates, evaluation of consciousness Deck (53):
- cannot be aroused
- deep vs light - in light reflex motor response can be aroused by noxious stimulus
- reduced consciousness
- can be aroused with intense or purposeful stimulation
range of stupor
drowsiness to deep stupor
- active and reversible state of consciousness
hysterical coma definition, how differentiated?
- feigned or subconsciously assumed depression of consciousness
- will have normal EEG, nystagmus on irrigation of auditory canal, no abnormal neurologic signs
explain the base of the pons exception
- most of the time when someone is conscious yet unresponsive it is obvious what (GB syndrome, MG, porphyria)
- damage to base of pons - patient becomes acutely unresponsive but will keep vertical and convergent eye movement, sight, and hearing
- LOCKED IN syndrome
reticular vs hemispheric involvement in depression of consciousness
- reticular involves mass lesions above or below the tentorium affecting reticular function (less common)
- hemispheric involvement is almost always metabolic and depresses the reticular formation indirectly
importance of cortical hemispheres in consciousness
- anything causing diffuse dysfunction of the cortex, whether destruction or encephalopathy, will cause stupor and/or coma
relationship between cortex and rostral reticular formation
- rostral reticular formation is termed the reticular activating system and the cortex can't function without it
- reticular activating system can work without cortex and maintain a crude sleep-wake vegetative state
- cortex is much more sensitive to toxic stimuli
common causes of direct damage to reticular formation
what part of the temporal lobe usually herniates the tentorial notch?
what pattern of deterioration is caused by tentorial notch herniation
order of brain deterioration in rostrocaudal process
evaluation of coma is primarily to differentiate between which two things?
- coma caused by diffuse cortical damage vs that caused by damage for reticular activating system
components of neuro eval of coma patient
- resp pattern
- pupil size
- oculomotor vestibular function
- motor function
what does drowsy look like?
opens eyes to stimulation but goes back to eyes closed when not stimulated
what does deep stupor look like?
needs vigorous stimulation to get response
what does deep coma look like?
no reaction even to noxious stimuli
if best motor response is withdrawal or posturing...
patient is not conscious
respiration in diffuse cerebral cortical dysfunction
- drowsiness, sighing respirations, yawning
when is a Cheyne Stokes resp pattern seen?
- damage to diencephalon or mesencephalon
- sometimes in diffuse cerebral cortical dysfunction
what is Cheyne Stokes respiration?
- crescendo-decrescendo pattern
- periods of apnea of variable length
when is Cheyne Stokes respiration most apparent?
respiration in damage to lower mesencephalon/upper pons
- central neurogenic hyperventilation, 20-40 rpm
- danger of respiratory alkalosis
- deep breathing
respiration in damage to lower pons
- irregularly irregular breathing
- inconstantly varying rhythm and rate
- may be hyperventilation
- may be apneustic breaths (hold after inspiration)
respiration in damage to medulla
- depression and ultimately apnea
pupils in isolated damage or diffuse damage to cerebral cortex
pupils in damage to diencephalon and why?
- constricted pupils because damage to thalamic pathways that carry sympathetic dilators
- still reactive to light
pupils in damage to caudal diencephalon/upper mesencephalon
- pupils sluggish in reacting to light
pupils in mesencephalon damage
- CNIII damage (loss of parasympathetics)
- pupils widely dilated (7-9mm)
- no reaction to light
pupils in damage to caudal levels of midbrain
- CNIII damage as in mesencephalon
- added damage to sympathetics
- pupils midsized (4-7mm)
- no reaction to light
pupils in damage to pons/medulla
- same as midbrain
- midsize and fixed
pupils in isolated pons or isolated medulla damage with maintained integrity of midbrain
- only loss of sympathetics
- very constricted pupils (1mm or less)
pupils in suppression of brainstem by drugs
- loss of light reflex
what happens in auditory ice water test if reticular formation is functional but there is diffuse cerebral damage?
- eyes go toward ice water side and stay there for minutes
- no nystagmus
in terms of eye movement, diffuse damage to cerebral cortex results in loss of.....
- fast component of vestibulo-ocular reflex (nystagmus)
- degree of suppression is proportionate to degree of damage
eye movements in damage to midbrain
dysconjugate eye movements
tonic conjugate deviation of the eyes during caloric stimulation indicates that....
the brainstem/reticular activating system is still intact
eye movement in damage to brainstem through the pons
- no reaction at all to caloric stimulation
- no corneal reflex
how will a lightly stuporous patient react to noxious stimuli?
- localize it
- knock it away or grab it
how will a deep stupor patient react to noxious stimuli?
- withdrawal (stereotyped)
noxious stimulation reaction of a comatose patient with damage to diencephalon
elements of decorticate posturing
- flexion of arms, wrists, fingers
- extension of lower limps
- may be asymmetric at first, appearing first on side of greater damage
noxious stimulation reaction of a comatose patient with damage to mesencephalon or upper pons
elements of decerebrate posturing
extension and internal rotation of arms and legs
what motor response is usually seen in pontine and medullary damage?
last reflex that can still be detected as metabolic dysfunction progresses
5 categories of metabolic dysfunction
examples of toxic metabolic dysfunction
endogenous - liver, kidney failure
exogenous - drug overdose
CNS - meningitis, encephalitis
what is most commonly the cause of depressed consciousness in a demented patient?
- demented patient's remaining cortical function is much more sensitive to stressors such as renal dysfunction, infections, drugs...
two major causes of vegetative state
- hypoxic ischemia
- shear force from trauma
are those in vegetative state conscious? aware?
no and no