Disorders of Consciousness Flashcards
Arousal
Level of consciousness, are the lights on?
Awareness
Content of consciousness, is anyone home
Is there a change in arousal with a transected medulla?
No, normal EEG. Only loss of arousal with transected mesencephlon (desynchronized EEG)
ARAS location and transmitter
Ascending reticular activating system, at the pontomesencephalic junction, acetylcholine
Neural correlates of arousal vs awareness?
Arousal: ARAS, thalamus, thalamo-cortical relays
Awareness: Cerebral cortex
Epidural hematoma causing disruptions in consciousness
Causes uncal herniation, which presses on the arousal centers in the brainstem
Thalamic Ischemia and consciousness
Disrupts
Cortical disruptions of consciousness
CJD causing spongiform encephalopathy
Levels of consciousness
Awake, drowsy, lethargic, obtunded, stuporous, comatose
What indicators are rated in the glasgow coma scale?
Verbal responsiveness, eye opening, motor responsivity
When you don’t know the where’s and why’s…
Listen to the breathing and look at the eyes.
Cheyne-Stokes Respiration
Caused by diffuse forebrain dysfunction, periodic non breathing, followed by crescendo breathing
Midbrain injury effect on breathing
Hyperventilation
Rostral Pons injury effect on breathing
Apneusis: Breaths followed by pauses, followed by shallow release
Caudal pons injury effect on breathing
Ataxic breathing, totally erratic
Medullary injury effect on breathing
Respiratory arrest
Control of pupillary sphincter
Light hits retinal cell, info transmitted to both edinger westphal nuclei. Via posterior commissure. Construction due to 3rd nerve
Carotid dissection
Can cause miosis because sympathetics going to eye ascend on internal carotid.
Thalamic pupils
Small reactive
Pretectal Pupil
Fixed Dilated
Herniation Pupil
One fixed dilated pupil
Pontine pupil
Pinpoint
Midbrain pupil
Fixed mid-size
Corneal Reflex
Afferent Limb: V1- CNV main nucleus in pons
Efferent Limb: CN VII orbicularis oculi – CNVII nucleus in pons
Doll’s Eye Reflex
If eyes don’t move when head is turning, the brainstem is not intact. Right side (PPRF) affected, can’t look right
Other test of brainstem function other than dolls eye?
Calorics
Upper midbrain damage effect on motor system
Decorticate posture – Flexors dominate
Upper pons damage effect on motor system?
Decerebrate Posture- extensors dominate
What looks like consciousness impairment, but isn’t?
Locked-in syndrome: Structural/functional brainstem transection just below mid-pons. ARAS - lies right above mid pons is responsible for preserved consciousness, but disruption of descending efferent pathways.
What can locked in people do?
Look up and down, convergence.
Vegetative state arousal vs consciousness
Arousal, no awareness
Coma/sleep/anesthesia arousal vs consciousness
No arousal, no awareness. Eyes closed
Minimally conscious state
Arousal, varying levels of awareness
Two types of vegetative states
Persistent vs permanent
Brain death
Absent midbrain reflexes (pupillary reactivity), absent pontine reflexes (VOR, corneal reflex), absent medullary reflexes (apnea)
