Consciousness Flashcards
consciousness
an active process often defined as awareness of the self and the environment
2 components:
arousal (wakefulness)
awareness (content)
arousal (wakefulness)
level of alertness
result of information arising from the reticular activating system
Other structures included: rostral pontine, mesencephalic tegmentum, midline, and intralaminar thalamic nuclei
awareness (content)
requires an intact cerebral cortex and its connections to other subcortical structures
cognition
- involves attention, sensation/perception, explicit memory, executive function and motivation
- depends on cerebral cortical activity
physiological vs. pathological unconsciousness
sleep is reversible with stimulation
pathological unconsciousness is due to structural or functional disturbances
ascending reticular activating system (ARAS)
- rostral brainstem tegmentum and diencephalon and associated cortical projections.
- signals related to level of arousal and awareness pass through the ARAS, are carried to the two thalami bilaterally, and then ascend to the rest of the cortex.
- signals are important for sleep- wake transitions and attention.
somnolence
drowsiness/near-sleep
lethargy
extreme fatigue or drowsiness
obtundation
mild to moderate reduction in alertness, w/ a lesser interest in environment
stupor
condition of deep sleep or similar behavioral unresponsiveness from which subject can be aroused only w/ vigorous and continuous stimulation
responds to VOICE, PAIN
coma
- unresponsive, sleep-like (but no cycles) state lacking arousal/awareness for 1+ hour
- movements=pathologic or do not exist
encephalopathy
- syndrome of global brain dysfunction
- states of altered consciousness caused by damage or suppression of the ARAS or of both cerebral hemispheres
Persistent Vegetative State:
+30days of complete unawareness with no localizing motor activity, no ability to follow commands (cortex NOT functioning)
- intact circulatory, brainstem, and respiratory function, normal sleep-wake cycles
- may spontaneously open eyes to stimuli but without recognition.
- often follows a pd of coma
Non-traumatic vegatative state 1+ month = _____ chance of recovery beyond severe disability.
Non-traumatic vegatative state 1+ month = NO chance of recovery beyond severe disability.
Traumatic state 1-6 months = _____ chance of recovery of good-moderate disability.
Traumatic state 1-6 months = 25% chance of recovery of good-moderate disability.
Minimally Conscious State (MCS)
- between PVS and normal consciousness
- can follow simple commands (yes/no responses via gestures or verbally)
- intelligible verbalization
- purposeful behavior (rather than reflexive)
which type of coma presents w/ NO eye movements
subcortical coma
brainstem is working but cortex is not –> which disturbance of consciousness?
persistent vegetative state
After TBI, MCS or PVS has a greater recovery?
MCS
locked-in syndrome
state of selective “de-effrentiation” of all 4 extremities and lower CN
- pt is awake, can hear
- NO movement and speech
- vertical eye movements/blinking possible (oculomotor spared)
- ventral pontine lesion
possible sites of lesions that compress the ARAS (compressive)
cerebral: bilateral subdural hematomas
diencephalon: thalamus (hemorrhage), hypothalamus (tumor)
brainstem: uncal herniation, cerebellum
possible sites of lesions that directly damage the ARAS (destructive)
cortex (acute anoxia)
subcortical (delayed anoxia)
diencephalon (thalamus infarct)
brainstem (midbrain, pons stroke)
multifocal and diffuse disease that may also lead to coma
Ischemia or hypoxia glucose disorders organ system diseases intoxication ionic or acid/base imbalances thermoregulation disorders infections cerebral vasculitis other (prion...)
how does intracranial HTN lead to altered consciousness?
elevated ICP –> decreases global cerebral blood flow –> compartmental changes in pressure –> herniation syndromes –> anatomical distortion of adjacent structures OR compression of vasculature causing infarcts
