Disorders of Consciousness Flashcards
(29 cards)
Disorders of consciousness:
Alterations in arousal and/or awareness
Disorders of consciousness: Arousal
- Arousal: physiological state of being alert and awake
Disorders of consciousness: Awareness
- Awareness: being responsive to stimuli (beyond reflexes)
4 states/examples of disorders of consciousness
- Coma
- Unresponsive wakefulness syndrome (UWS)
- Cognitive motor dissociation (CMD)
- Minimally conscious state (MCS)
What is a coma?
- Greek kōma - trance or deep sleep
- Complete absence of arousal and awareness
- No eye opening, verbal responses, motor responses (except maybe posturing to pain)
How does a coma affect the brainstem?
- Deceberate - lower brainstem
- Decorticate -> deceberate = brainstem is slowly dying DOWNWARS
Decorticate posturing
- Pointed and turned in toes
- Rigid, extended legs
- Arms bent toward center of body
- Curled wrists and balled hands against chest
Deceberate posturing
- Pointed and turned in toes
- Rigid, extended legs
- Flexed wrists
- Curled fingers
- Straight, tense arms parallel to body
Coma pathogenesis/variety of injuries possible
- Bihemispheric lesions (both sides of cortex)
- Bilateral lesions of pons
- Widespread dysfunction affecting corticothalamic system
- Other combinations of brainstem structures
Possible causes of injury resulting/leading to coma
- TBI
- Stroke (ischemic, hemorrhagic)
- Global decrease in blood flow to brain following cardiac event (hypoxic, ischemic encephalopathy)
- Seizure, sedating medication
Key component/COMMON FEATURE of injury -> coma:
- widespread downregulation of neural firing resulting in disfacilitation – resting membrane potential becoming more negative (hyperpolarizes) in cortex, thalamus, and striatum (component of basal ganglia)
Unresponsive wakefulness syndrome (PREVIOUS: vegetative stage)
- (UWS, formerly vegetative state): arousal without awareness
- Preserved physiological functions (cardiac, respiratory, sleep/wake cycles) without clear signs of awareness of the self or the environment
- Only reflexive behaviours
Cognitive Motor Dissociation
- CMD, “covert consciousness”, or “locked-in syndrome”: volitional brain activity detectable by imaging with no external behaviour
- Some amount estimated at 20% of those who appear unaware
Discovery of Cognitive motor dissociation
- 25-year-old unresponsive woman 5 months after a severe TBI
- In fMRI, instructed to perform two mental imagery tasks
- Demonstrated preserved intentionality and Awareness
Covert consciousness can be detected with..
What types of scans?
EEG or fMRI
TIMING - among patients with changes to consciousness, they received EEG after…
- 67% following TBI
- 60% following ischemic stroke
- 33% after hemorrhagic stroke
- 25% if no clear injury
Minimally conscious state
- MCS: minimal but inconsistent awareness
- Shows some oriented (environmentally contingent) behaviours not attributable to reflexes
Difference between MCS +/-
- MCS+: with language
- MCS-: without language
What scale is patient consciousness measured on?
- Glasgow Coma Scale: standardized way to evaluate the level of consciousness of patients with a brain injury
- (step 0 of the neurological exam - “make sure the person is aware”)
What 3 components of the Glasgow Coma Scale are measured?
- Eyes
- Verbal
- Motor
Eyes
What 3 components of the Glasgow Coma Scale are measured?
- Spontaneous (normal)
- To sound
- To pressure
- None
Verbal
What 3 components of the Glasgow Coma Scale are measured?
- Orientated (normal)
- Confused
- Words
- Sounds
- None
Motor
What 3 components of the Glasgow Coma Scale are measured?
- Obey command (normal)
- Localises
- Normal flexion
- Abnormal flexion
- Extension
- None
Behaviour across DoC states: COMA
Eye opening, Movement, Response to Pain, Respone to Command, Verbalization
- Eye opening: NONE
- Movement: NONE
- Response to Pain: NONE/POSTURING
- Respone to Command: NONE
- Verbalization: NONE
