Lecture 53: Disorders of consciousness Flashcards
What is the location of the source nuclei for the ascending reticular activating system (ARAS)? NT?
Ponto-mesencephalic junction; ACh
Pathway (three regions) responsible for “arousal”
ARAS –> thalamus –> thalamo-cortical relays
Brain region responsible for “awareness.” Is it easy to “knock the lights out” here?
Cortex; NO – would have to damage cortex BILATERALLY to cause loss consciousness
What type of stroke can cause mass effect? What brain region can this effect?
Epidural hematoma; brainstem
What scary transmitted disease can cause loss of consciousness at the level of the cortex?
Creutzfeld-Jacob Disease (CJD)
Levels of consciousness/arousal (6)
Awake, somnolent (full arousal by auditory/tactile), lethargic (sub-arousal by non-noxious), obtunded (depressed LOC, still responds to non-noxious), stupor (req noxious stimuli), coma (unresponsive)
Content of consciousness: levels of awareness (3)
Alert –> inattentive –> vegetative
Neurologic examination of coma features (3, if you don’t know the wheres or the whys…)
Respiratory pattern, eye function, motor responsitivity (listen to breath and look at the eyes)
Respiratory pattern w/ forebrain dysfunction
Cheyne-Stokes respiration (hyperventilation with pauses)
Respiratory pattern w/ midbrain dysfunction
Hyperventilation
Respiratory pattern w/ rostral pons dysfunction
Apneusis
Respiratory pattern w/ caudal pons dysfunction
Ataxic breathing (disorganized)
Respiratory pattern w/ medulla dysfunction
Respiratory arrest
Pupil patterns w/ thalamic dysfunction
Small reactive
Pupil patterns w/ herniation
One fixed dilated (impacting para on CN III)
Pupil patterns w/ pretectal dysfunction
Fixed dilated
Pupil patterns w/ midbrain dysfunction
Fixed mid-size
Pupil patterns w/ pontine dysfunction
Pinpoint
Corneal reflex (afferent/efferent). Lesions localize where?
Afferent: CN V; Efferent: CN VII; pons
Two clinical provocative maneuvers for VOR
Oculo-cephalic/Doll’s eyes reflex; calorics
Oculo-cephalic reflex
Tests VOR: eye tilt to provoked head movements
Oculo-cephalic reflex w/ right lateral pontine lesion
Cannot look to the right (no pontine lateral gaze function)
Cold water calorics w/ right lateral pontine lesion
No slow gaze drift to the right side
Oculo-cephalic reflex w/ bilateral midbrain lesion
Turn right: cannot adduct right eye; Turn left: cannot adduct left eye; Turn up/down: eyes stay still
Cold water calorics w/ bilateral midbrain lesion
Cannot adduct proper eye during application to either ear (no medial rectal activity in III)
In full consciousness, what happens to Doll’s eye reflex?
+ or - due to ability to inhibit it
With knocked out cortex but OK brain stem, what happens to Doll’s eye reflex?
+
With knocked out cortex AND brain stem, what happens to Doll’s eye reflex?
-
Descriptive characteristics of motor responsivity (6)
Purposeful, localize, withrdaw, decorticate, decerebrate, none
Knocked out motor cortex/thalamus…
No contralateral purposeful movement
Knocked out upper midbrain…
Flexion response/ decorticate posture (high lesion, body goes up)
Knocked out upper pons…
Extension response/ decerebrate posture (low lesion, body goes down)
What eye movements are spared in locked-in syndrome
Voluntary opening, vertical movements, covergence
Categories of consciousness impairment (3 w/ subtypes for 1)
Coma, vegetative (persistent, permanent), minimally conscious
Arousal/awareness in vegetative state
Full arousal, no awareness
Arousal/awareness in minimally conscious state. Describe.
Full arousal, fluctuating partial awareness (eye movements, simple commands, purposeful behavior)
Arousal/awareness in coma
No arousal, no awareness
T/F: Sleep wake cycles in vegetative state
True
Main point of coma prognosis
Longer the absence of key brainstem function signs (breathing, motor responsivity, eyes) = worse prognosis
Brain death
Absent midbrain reflxes (pupillary reactivity); absent pontine reflexes (VORs, corneal); absent medullary reflexes (apnea)
To determine brain death, must do…(2)
Brain stem function testing; apnea testing
