Conciousness Flashcards
Give examples of roles that will have different views on the definition of consciousness.
Philosopher
Psychologist
Neuroscientist
Neurosurgeon
What is consciousness?
‘Awareness of Awareness’ - some suggest it is fundamentally a function of the brain with neural mechanisms involved whereas others resist reducing consciousness believing that it cannot be explained in reductionalist physical terms
Damage to what structures change a patient’s level of consciousness?
- Reticular formation
- Intralaminar thalamic nuclei (bilateral lesion)
- Cerebral hemispheres (bilateral involvement)
- Dominant hemisphere (major involvement)
- NS (generalised depression)
What is the reticular formation?
Network of reticular fibres synapsing with ascending and descending tracts beginning in medulla and extending to mid-brain with long dendrites radiating to brainstem occupying a significant portion of dorsal brainstem
What is the major role of the reticular formation?
Sleep/wake cycle
What is the reticular activating system?
A network of structures including brainstem, thalamus and neural pathways that function together to produce and maintain arousal
What is the medical perspective of consciousness?
A state of being aware of (or responsive) to the environment with the ability to perceive, physically or mentally, what is happening
What is the role of the reticular activating system?
The part of reticular formation in brainstem playing a central role in bodily and behavioural alertness (arousal)
What are causes of a decrease in conscious level?
Trauma Infection Tumour Metabolic Intoxication
What types of trauma can cause a decrease in consciousness?
Minor concussion
Cerebral contusion
Intracranial/intraparaenchymal aemorrhage
What types of infection can cause a decrease in consciousness?
Meningitis
Encephalitis
Brain abscess
Subdural empyema
What types of tumour can cause a decrease in consciousness?
Benign (e.g. meningioma and malignant (e.g. glioma) all of which can be complicated by development of surrounding oedema due to raised ICP
What types of metabolic problems can cause a decrease in consciousness?
Hypoperfusion/hypoxaemia Hypoglycaemia Hyperglycaemia/DKA Hyper/hypo-natraemia Hypercalcaemia Renal/liver failure Hypothermia
What different ways can a person become hypoperfused/hypoxaemic?
Syncope
Stroke
TIA
What types of intoxication can cause a decrease in consciousness?
Medication Illegal drugs Toxins Alcohol Narcotics
What did the old assessment of consciousness include?
Scales of different levels:
- Normal
- Obtundation (confusion)
- Stupor
- Coma (unconsciousness)
What is obtundation?
Awareness impaired but may become normal or nearly so on arousal, speech slow, voluntary movements diminished + slow, EECG mildly abnormal with some sleep pattern (GCS = 11-12/15)
What is stupor?
No real awareness, speech only in response to pain, voluntary movements minimal or there may be mass movements in response to pain, EEG abnormal but distinguishable from normal sleep pattern (GCS = 8-10/15)
What is coma?
No awareness, speech absent, movements absent or only reflex in response to pain, EEG grossly abnormal or absent (GCS 0-8/15)
What does the modern assessment of consciousness use?
Glasgow Coma Score (GCS)
What does the Glasgow Coma Score (GCS) test?
Best eye (E), verbal (V) and motor (M)response
How is best eye response (E) ranked in the Glasgow Coma Score (GCS)?
4 - eyes open spontaneously
3 - eyes open to speech
2 - eyes open to painful stimulus
1 - no eye opening
How is best verbal response (V) ranked in the Glasgow Coma Score (GCS)?
5 - fully orientated in time, place + person 4 - confused (disorientated) 3 - inappropriate words 2 - incomprehensible sounds 1 - none
How is best motor response (M) ranked in the Glasgow Coma Score (GCS)?
6 - obeys commands 5 - localises to painful stimulus 4 - withdrawal from pain 3 - abnormal flexes to pain 2 - extends to pain 1 - no motor response
What painful stimuli do you utilise when testing best motor response (M) in the Glasgow Coma Score (GCS)?
Squeeze supraoptic area
What does a score of 3 and 2 mean on the best motor response (M) scale of the Glasgow Coma Scale (GCS)?
3 = abnormal flexes to pain means the cerebral cortex is not functioning properly
2 = extends to pain so anything above the brainstem is not functioning
How do you interpret the Glasgow Coma Scale (GCS)?
15 = best possible i.e. normal 3 = worst possible
E.G. GCS 7 (E1, V2, M4)
What scores will different severity of head injury show on the Glasgow Coma Scale (GCS)?
Minor = More than 13 Moderate = GCS 9-12 Severe = GCS less than 8
What is a persistent vegetative state?
Reticular formation intact but connection with cerebral cortex non-functional so person is awake (eyes open, move around but dont fix on anything + sleep/wake cycles present) but awareness is absent along with meaningful response to verbal command or pain
What would an electroencephalography (EEG) show on a patient in a persistent vegetative state?
Contains rhythmic activity resembling sleep cycles
What is locked-in syndrome?
Sensation, reticular formation and cortical function intact so person is fully awake and aware but motor function is absent although vertical eye movements and eyelid elevation may be spared usually due to infarct in ventral pons involving CBT/CST
What is the pneumonic for cranial nerves (CNs)?
Oh Oh Oh To Touch A Fair Virgin Girls Vagina And Hymen
What are the 12 cranial nerves (CNs)?
Olfactory (I) Optic (II) Occulomotor (III) Trochlear (IV) Trigeminal (V) Abducens (VI) Facial (VII) Vestibulocochlear (VIII) Glossopharyngeal (IX) Vagus (X) Accessory (XI) Hypoglossal (XII)
What does a peripheral neurological evaluation test?
Tone (normal/hypo/hyper) Power (scoring system) Reflexes Co-ordination Sensation (dermatomes/myotomes)
What is the scoring system for tone?
1 = none 2 = move but not against gravity 3 = able to move against gravity 4 = less than normal power 5 = normal
Why do a peripheral neurological examination?
To check for UMN and/or LMN lesions
