L56 Consciousness

Question 1

define consciousness

Answer 1

the ability to be aware of oneself and ones place in the environment

the ability to respond appropriately to environmental stimuli

*easy to define, but no one knows how it works

Question 2

what does consciousness depend on?

Answer 2

synchronization of cortical neurons that fire around 40Hz

Question 3

what does consciousness result from?

Answer 3

important functions of brain activity

• memory
• learning
• distinguishing self from non-self
• re-entry

Question 4

define re-entry

Answer 4

the recursive comparison of info by different brain regions

Question 5

where is the re-entry mechanism located?

Answer 5

in circuits of the thalamocortical system

Question 6

define coma

Answer 6

nonsleep, loss of consciousness that (unlike syncope) lasts for an extended period of time

Question 7

what are the levels of unconsciousness?

Answer 7

• lethargic
• obtunded
• stuperous
• comatose

Question 8

define lethargic

Answer 8

pt can be fully aroused

Question 9

define obtunded

Answer 9

pt cannot be fully aroused

Question 10

define stuporous

Answer 10

sleep like status

Question 11

define comatose

Answer 11

no purposeful response to stimuli

Question 12

what does the brainstem play an important role in?

Answer 12

condition of consciousness
attentive vigilance
wake-sleep rhythm

Question 13

lesions to what can impair consciousness?

Answer 13

thalamus
midbrain
or both cerebral hemispheres

Question 14

describe the brainstem and its link to consciousness

Answer 14

1. Cells of the midbrain (reticular formation) receive ascending info from the spinothalamic track and other
2. They are projected via 2 branches to higher cortical centers
   - To the thalamus→ activating and modulating
   thalamic relay nuclei and intralaminar nuclei
   - To the lateral hypothalamic area→ which is joined by ascending output from hypothalamic and basal forebrain cells

Question 15

define the transmission mode

Answer 15

• resting potential is near firing threshold
• cholinergic input from pons and basal forebrain is present
• EEG shows DEsynchronized pattern - LOW voltage, HIGH frequency

wakefulness and awareness

Question 16

define Burst mode

Answer 16

• neurons hyper polarized by inhibitory GABA from reticular formation input
• EEG shows Synchronized wave patterns - HIGH voltage, LOW frequency

deep sleep and coma

Question 17

what is coma?

Answer 17

A deep state of unconsciousness; unable to move or respond to environmental stimuli

Raw definition→ not opening eyes, not obeying commands and not uttering understandable words

Question 18

what are the common causes of coma?

Answer 18

Commonly caused by head injury or complications to another disease (ie: brain tumor or ↑ICP)

Question 19

what brain structure is involved in Vegetative state?

Answer 19

cortex/higher centers

Question 20

Describe Vegetative state

Answer 20

-A complete loss of higher brain function (cortex) however maintain breathing and circulatory functions
-Spontaneous movements can occur such as eye opening to painful external stimuli but are unable to
respond to commands, to speak or respond meaningfully to environmental stimuli
-Pt may cry, grimace or laugh but this is not the result of them interpreting and responding meaningfully.

Question 21

what brain structure is involved in brain death?

Answer 21

all brain including the brainstem

Question 22

describe brain death

Answer 22

Denotes the irreversible loss of all brain functions
determined by
-No electrical brain activity (isoelectric EEG)
-Absence of brain→ no movement, response to stimuli, breathing or brainstem reflexes

Question 23

what are common causes of brain death?

Answer 23

• Anoxia (suffocation; can be drug, respiratory disease, etc)
• Ischemia (vascular occlusion)
• Intracranial Hemorrhage
• Trauma
• Brain Tumors
• ↑ICP and uncal herniation

Question 24

what brain structure is involved in Locked-in-syndrome

Answer 24

pons

Question 25

describe Locked-in-syndrome

Answer 25

- Blockage of basilar artery causing massive infarction to pons - Causes total paralysis of voluntary muscle except for vertical eye movement muscles and opening lid - Pts are fully aware but cant move and communicate via vertical eye movements and opening the eyelid

Question 26

what causes loss of consciousness?

Answer 26

- damage to the reticular formation in the midbrain - damage to either branch of the ascending arousal system - impairment of thalamus - bilateral impairment of the cerebral hemispheres

Question 27

what is the Glasgow coma scale

Answer 27

scored between a 3 and 15

Question 28

what 3 parameters are evaluated in the GCS

Answer 28

best eye response best verbal response best motor response

Question 29

what is the criteria to grade best eye response?

Answer 29

``` (4) 1 - no eye opening 2 - eye opening to pain 3 - eyes opening to verbal command 4 - eyes open spontaneously ```

Question 30

what is the criteria to grade best verbal response?

Answer 30

``` (5) 1 - no verbal response 2- incomprehensible sounds 3 - inappropriate words 4 - confused 5 - orientated ```

Question 31

patients who score less than or equal to 8 on GCS are what?

Answer 31

90% in coma

Question 32

patients who score greater than or equal to 9 on GCS are what?

Answer 32

not in coma

Question 33

what is the critical score of GCS?

Answer 33

8

Question 34

what score describes moderate severity of the GCS

Answer 34

9-11

Question 35

what score describes minor injury of the GCS?

Answer 35

12-15

Question 36

where is the lesion associated with Cheyne-Stokes respirations?

Answer 36

forebrain lesions

Question 37

where is the lesion associated with apneusis (inspriatory cramps) respirations?

Answer 37

lesion in pons

Question 38

where is the lesion associated with hyperventilation respirations?

Answer 38

lesion in midbrain

Question 39

where is the lesion associated with ataxic breathing respirations?

Answer 39

lesion in lower pons/upper medulla

Question 40

what damage is associated with decorticate posturing?

Answer 40

damage to upper midbrain (bilteral)

Question 41

what damage is associated with decerebrate posturing?

Answer 41

damage to upper pons or lower midbrain (bilateral)

Question 42

with respect to the pupillary light response, what does small reactive pupils indicate?

Answer 42

- diffuse forebrain impairment (metabolic encephalopathy) - pontine injury - sedative drugs (opiates)

Question 43

with respect to the pupillary light response, what does mid positional pupils and loss of response indicate?

Answer 43

-structural injury (almost always) damage of CN III at level of midbrain

Question 44

with respect to the pupillary light response, what does unilateral pupillary dilation indicate?

Answer 44

- injury of CN III at the exit of brainstem | - unilateral compression (aneurysm of post. communicating a., tumor, increased ICP --> uncial herniation)

Question 45

with respect to the pupillary light response, what does large, unreactive pupils indicate?

Answer 45

pressure in pretectal area (pineal tumor)

Question 46

with respect to oculomotor responses, describe metabolic encephalopathy?

Answer 46

- dolls head maneuver - eyes roll counter head movement | - cool water in ear - eyes turn to same side = brainstem intact

Question 47

with respect to oculomotor responses, describe a right pontine lesion?

Answer 47

Dolls Test 1. Head  to  right→  normal  (eyes  to  left) 2. Head  to  left→  no  movement  at  all COWS 1. Cold  in  right→  no  movement 2. Cold  in  left→  normal  (eyes  to  left) gaze paralysis to the right, because right PPRF and /or right CN VI is lesioned

Question 48

with respect to oculomotor responses, describe a midbrain lesion?

Answer 48

Dolls Test 1. Head  to  left→  right  eye  normal  but  left  is  unresponsive 2. Head  to  right→  left  eye  normal  but  right  is  unresponsive COWS 1. Cold  in  right→  right  eye  normal  but  left  is  unresponsive 2. Cold  in  left→  left eye normal but right eye is unresponsive *This lesion involves both occulomotor nuclei causing loss in Medial Rectus, thus loss of aDduction