Lecture 53: Disorders of consciousness

Question 1

What is the location of the source nuclei for the ascending reticular activating system (ARAS)? NT?

Answer 1

Ponto-mesencephalic junction; ACh

Question 2

Pathway (three regions) responsible for “arousal”

Answer 2

ARAS –> thalamus –> thalamo-cortical relays

Question 3

Brain region responsible for “awareness.” Is it easy to “knock the lights out” here?

Answer 3

Cortex; NO – would have to damage cortex BILATERALLY to cause loss consciousness

Question 4

What type of stroke can cause mass effect? What brain region can this effect?

Answer 4

Epidural hematoma; brainstem

Question 5

What scary transmitted disease can cause loss of consciousness at the level of the cortex?

Answer 5

Creutzfeld-Jacob Disease (CJD)

Question 6

Levels of consciousness/arousal (6)

Answer 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)

Question 7

Content of consciousness: levels of awareness (3)

Answer 7

Alert –> inattentive –> vegetative

Question 8

Neurologic examination of coma features (3, if you don’t know the wheres or the whys…)

Answer 8

Respiratory pattern, eye function, motor responsitivity (listen to breath and look at the eyes)

Question 9

Respiratory pattern w/ forebrain dysfunction

Answer 9

Cheyne-Stokes respiration (hyperventilation with pauses)

Question 10

Respiratory pattern w/ midbrain dysfunction

Answer 10

Hyperventilation

Question 11

Respiratory pattern w/ rostral pons dysfunction

Answer 11

Apneusis

Question 12

Respiratory pattern w/ caudal pons dysfunction

Answer 12

Ataxic breathing (disorganized)

Question 13

Respiratory pattern w/ medulla dysfunction

Answer 13

Respiratory arrest

Question 14

Pupil patterns w/ thalamic dysfunction

Answer 14

Small reactive

Question 15

Pupil patterns w/ herniation

Answer 15

One fixed dilated (impacting para on CN III)

Question 16

Pupil patterns w/ pretectal dysfunction

Answer 16

Fixed dilated

Question 17

Pupil patterns w/ midbrain dysfunction

Answer 17

Fixed mid-size

Question 18

Pupil patterns w/ pontine dysfunction

Answer 18

Pinpoint

Question 19

Corneal reflex (afferent/efferent). Lesions localize where?

Answer 19

Afferent: CN V; Efferent: CN VII; pons

Question 20

Two clinical provocative maneuvers for VOR

Answer 20

Oculo-cephalic/Doll’s eyes reflex; calorics

Question 21

Oculo-cephalic reflex

Answer 21

Tests VOR: eye tilt to provoked head movements

Question 22

Oculo-cephalic reflex w/ right lateral pontine lesion

Answer 22

Cannot look to the right (no pontine lateral gaze function)

Question 23

Cold water calorics w/ right lateral pontine lesion

Answer 23

No slow gaze drift to the right side

Question 24

Oculo-cephalic reflex w/ bilateral midbrain lesion

Answer 24

Turn right: cannot adduct right eye; Turn left: cannot adduct left eye; Turn up/down: eyes stay still

Question 25

Cold water calorics w/ bilateral midbrain lesion

Answer 25

Cannot adduct proper eye during application to either ear (no medial rectal activity in III)

Question 26

In full consciousness, what happens to Doll's eye reflex?

Answer 26

+ or - due to ability to inhibit it

Question 27

With knocked out cortex but OK brain stem, what happens to Doll's eye reflex?

Answer 27

+

Question 28

With knocked out cortex AND brain stem, what happens to Doll's eye reflex?

Answer 28

-

Question 29

Descriptive characteristics of motor responsivity (6)

Answer 29

Purposeful, localize, withrdaw, decorticate, decerebrate, none

Question 30

Knocked out motor cortex/thalamus...

Answer 30

No contralateral purposeful movement

Question 31

Knocked out upper midbrain...

Answer 31

Flexion response/ decorticate posture (high lesion, body goes up)

Question 32

Knocked out upper pons...

Answer 32

Extension response/ decerebrate posture (low lesion, body goes down)

Question 33

What eye movements are spared in locked-in syndrome

Answer 33

Voluntary opening, vertical movements, covergence

Question 34

Categories of consciousness impairment (3 w/ subtypes for 1)

Answer 34

Coma, vegetative (persistent, permanent), minimally conscious

Question 35

Arousal/awareness in vegetative state

Answer 35

Full arousal, no awareness

Question 36

Arousal/awareness in minimally conscious state. Describe.

Answer 36

Full arousal, fluctuating partial awareness (eye movements, simple commands, purposeful behavior)

Question 37

Arousal/awareness in coma

Answer 37

No arousal, no awareness

Question 38

T/F: Sleep wake cycles in vegetative state

Answer 38

True

Question 39

Main point of coma prognosis

Answer 39

Longer the absence of key brainstem function signs (breathing, motor responsivity, eyes) = worse prognosis

Question 40

Brain death

Answer 40

Absent midbrain reflxes (pupillary reactivity); absent pontine reflexes (VORs, corneal); absent medullary reflexes (apnea)

Question 41

To determine brain death, must do...(2)

Answer 41

Brain stem function testing; apnea testing