G05--> Consciousness Flashcards
what is consciousness?
awareness of one’s self and one’s place in the environment with the ability to respond appropriately to environmental stimuli
Consciousness results from what important functions of the brain
memory, learning, self from non self and re entry (Where mechanisms located in thalamocortical system)
what is a coma?
Non-sleep LOC lasting for extended period of time (unlike syncope)
what are the levels of unconsciousness?
- Lethargic –> patient can be fully aroused
- Obtunded –> patient can not be fully aroused
- Stuporous—> sleep like status
- Comatose –> no purposeful response
Describe the ascending reticular activating system of the ascending arousal system responsible for consciousness
Cell groups in the reticular formation of the midbrain receive collateral connections of ascending pathways (spinothalamic tract, spinal tract of V, solitary tract, vestibular and cochlear nuclei, olfactory and optic system)and project via 2 branches to higher centers of the cerebral cortex
what are the two projected branches to higher cortical centers
- To 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
What would happen to the patient if either of these pathways are lesioned?
the thalamus, midbrain or cerebral hemispheres can impair consciousness
The brainstem plays an important role for what?
condition of consciousness, attentive vigilance and wake-sleep rhythm
Thalamic relay neurons have 2 physiological states: describe each one
- Transmission Mode –> wakefulness and awareness
a. resting potential is near firing threshold
b. cholinergic input from pons and basal forebrain is present
c. EEG shows desynchronized pattern -> low voltage and high frequency
(look at the notes for the image of the EEG)
what is the second physiological state
- Burst Mode –> deep sleep and coma
a. neurons hyperpolarized by inhibitory GABA from reticular formation input
b. EEG shows synchronized wave pattern –> high voltage and low frequency
what is a coma?
a deep state of unconsciousness; unable to move or respond to environmental stimuli
what are some common causes of coma?
head injury or complications to another disease (Brain tumor or increased intracranial pressure)
Supratentorial mass lesion (epidural hemorrhage, subdural hemorrhage)
Subtentorial lesions (brain stem infarction, brain stem tumor, cerebellar hemorrhage)
Metabolic and diffuse cerebral disorders (anoxia or ischemia, concussions, infection)
always has to be on both sides!
what symptoms do you see on examination of a coma patient?
not opening eyes, not obeying commands and not uttering understandable words
Where is the lesion in a vegetative state?
cortex/higher centers
complete loss of higher brain function (cortex) however maintain breathing and circulatory functions
Can spontaneous movements occur?
yes they 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
the patient may cry, grimace or laugh what is this not a result of?
not the result of them interpreting and responding meaningfully
what is lesioned if a patient is brain dead?
all brain including brainstem
denotes the irreversible loss of all brain functions
What is required in order to pronounce someone brain dead?
no electrical brain activity (isoelectric EEG)
absence of brain –> no movement, response to stimuli, breathing or brainstem reflexes
no corneal reflex
no vestibulo ocular reflex (ice water in ear)
pupils dilated and not reactive to light
what are the possible causes for brain death?
Anoxia (suffocation; can be drug or resp disease)
Ischemia (Vascular occlusion)
Intracranial hemorrhage
trauma
brain tumors
increased intracranial pressure and uncal herniation
what are the specific brainstem reflex losses?
no response to speech/pain/etc no respirations pupils fixed/dilated no vor No corneal reflex
where is the lesion at in the locked in syndrome?
blockage of the basilar artery resulting in massive infarction of the pons
what is the main syndrome of locked in syndrome?
complete paralysis of voluntary muscles in all parts of the body except for those that control vertical eye movements.
patients with locked in syndrome are fully aware of their environment and can think but what can they not do?
unable to speak or move. communication is possible only by vertical eye movements and opening the eyelid
what are some common causes of coma?
head injury or complications to another disease (Brain tumor or increased intracranial pressure)
always has to be on both sides!
The causes of coma are in specific areas of the brain describe the areas affected and how these areas result in coma?
Supratentorial mass lesions
- epi/subdural/intracranial hemorrhage
- cerebral infarction
- brain tumor or abscess
what is the second area affected?
Subtentorial Lesion:
- Brain stem–> infarc, tumor or hemorrhage
- Cerebellar –> hemorrhage or abscess
what is the third area affected?
metabolic and diffuse cerebral disorders:
a. anoxia, ischemia, concussions, seizures, infection, subarachnoid blood
b. hypo/hyper glycemia-natriemia
c. hypothyroidism, hypocortisolism, hypercarbia
d. drugs, liver failure, sepsis
Remember the Glasgow Coma Scale (IT STALKS YOU)!!!
GCS is scored between 3 and 15 3 being the worst 15 being the best best eye response (4) CP best verbal response (5): CCWS best motor response (6): LWFE
Respiratory patterns will vary based on the lesion site: what are these patterns
- lesion in forebrain –> cheyne stokes respiration
- lesion in pons –> apneusis (inspiratory cramps)
- lesion in medulla (bilateral) –> respiratory arrest
- Lesion in midbrain –> hyperventilation
- Lesion in lower pons/upper medulla –> ataxic breathing
There are levels of arousal and motor response what are they?
response to verbal instruction
response to local painful stimulation
if upper midbrain (bilateral)–> decorticate posturing
if lower midbrain/upper pons –> decerebrate posturing
There are numerous pupillary light responses based on the impairment, each card will go through the response based on the damage
- Small reactive pupils (diencephalic)—> diffuse forebrain impairment (metabolic encephalopathy), pontine injury or sedative drugs (opiates)
2nd pupil light response
- Midposition pupils and loss of pupillary response –> structural injury (almost always) damage of III at level of midbrain
3rd pupil light response
- Unilateral pupillary dilation –> injury of III at exit of brain stem, unilateral compression (aneurysm of posterior communication artery, tumor, increased intracranial pressure –> uncal herniation)
4th pupil light response
- Large, unreactive pupils –> pressure in pretectal area (pineal tumor)
if there is a lesion in the pons, what is the pupillary light response?
pinpoint
If a patient presents with metabolic encephalopathy what tests would you perform to test the oculomotor response?
- Dolls head maneuver: eyes roll counter head movement
- Cold water in ear: eyes turn ipsilateral side –> brain stem intact (normal response)
remember COWS
If a patient has a right pontine lesion what tests would you perform to check the oculomotor function?
- Dolls head maneuver: head to the right (eyes roll counter head movement) and head to left (no eye movement relative to head movement)
- Cold water: cool water in right ear (eyes dont turn to the right), cool water in left ear (eyes turn to the left), cool water in both ears (eyes turn to the left)
Gaze paralysis to the right, because right PPRF and/or right CN VI is lesioned.
remember COWS
If a patient has a midbrain lesion what eye symptoms are seen?
this lesion involves both oculomotor nuclei causing loss of medial rectus thus loss of adduction but abduction is still possible! Vertical eye movements are usually impaired because damage to MRF which does vertical movements.
down and out presentation
How would you test a patient with a midbrain lesion for oculomotor function?
- Dolls test: head to left –> right eye normal but left is unresponsive and head to right –> left eye normal but right is unresponsive
- COWS: cold in right –> right eye normal but left is unresponsive and cold in left –> left eye normal but right eye is unresponsive.
