Lecture 10.2: Assessment of Consciousness Flashcards
What is Consciousness?
- Your awareness of external events
- Your awareness of internal sensations
- Your awareness of yourself as a unique being
having experiences - Your awareness of your thoughts about these
experiences
Theories on the Origins of Consciousness (4)
- Creation: God’s gift.
- None: consciousness is mythical, like demons.
- By-product of evolution of cognitive complexity.
- Evolution by natural selection: increases ability to
survive and reproduce.
Levels of Awareness (6)
- Awake
- Sleep
- Anaesthesia
- Coma
- Persistent Vegetative State
- Death
What is Brain Death?
- Total unawareness of externally applied stimuli
- No movements or breathing during a period of at
least one hour - No reflexes
- Flat EEG (no brain waves)
What does Anaesthesia do to consciousness?
- Anaesthetics inhibit neuronal activity
- As anaesthetic dose is increased, metabolic
activity in the brain decreases - At some point, consciousness is abruptly lost
- Activity in high order association areas is reduced
- Significant decrease in thalamic activity
What is the Reticular Activating System?
Diverse spread of interconnected nuclei in the brainstem that send projections to a range of cortical and spinal regions
What is Coma?
- A sleep like state with no purposeful response
from which the patient cannot be aroused - Due to disturbance in function of brainstem,
reticular activating system or both hemispheres
What is Stupor?
State of reduced consciousness where patient may show poorly directed reflexes to physical stimuli
What can cause altered consciousness? (10)
- Abnormal Glucose Levels
- Trauma
- Renal Failure
- CO Poisoning
- Infection
- Hepatic Failure
- Hypoxia
- Drugs
- Seizures
- Abscess
What is a Extra/Epidural Haemorrhage?
Haemotoma between between inner table of skull and dura
What is the most common source of bleeding in an Extra/Epidural Haemorrhage?
A torn middle meningeal artery (90%)
What is the less common source of bleeding in an Extra/Epidural Haemorrhage?
Venous EDH from dural venous sinus
What is the most common cause of a EDH?
Typically young patient following sport or RTA
How does a EDH present?
- May or may not lose consciousness
- Lucid interval
- Ongoing headache
- Collapse few hours later
- Urgent neurosurgical input
What is the shape of an EDH?
Typically biconvex in shape and can cause a mass effect
What is the shape of a Subdural Haemorrhage?
- Typically crescentic (crescent moonshaped)
- More extensive than EDH
- Internal margin paralleling the cortical margin of
the adjacent brain
What is the source of bleeding in a Subdural Haemorrhage?
Venous: torn bridging veins that cross the Dural sinuses
How do Subarachnoid Haemorrhages present?
- Patients typically present with a thunderclap.
headache - Usually the worst headache of their lives
- It is associated with collapse and loss of
consciousness
What can cause a Subarachnoid Haemorrhages? (2)
- Trauma (with associated cerebral contusion)
- Spontaneous: ruptured berry aneurysm (85%)
Base of Skull Fracture Signs (6)
- Raccoon Eyes
- CSF Rhinorrhea
- CSF otorrhea
- Battle Sign (bruising over the mastoid process)
- Haemotympanum
- Bump
Signs of a Skull Fractures (11)
- Bleeding
- Bruising
- Altered Consciousness
- Neurological Signs
- Battle’s Sign
- Racoon Eyes
- CSF Rhinorrhoea
- Cranial Nerve Palsy
- Hemotympanum
- Deafness
- Nystagmus
What can cause raised ICP? (3)
- Mass – intrinsic = tumour, extrinsic = haematoma
- Diffuse brain swelling
- Impaired circulation/absorption of CSF
What is Cushing’s Triad? (3)
- Hypertension
- Bradycardia
- Decreased Respirations
What can raised ICP cause to happen to the brain?
Herniations
What is Cingulate Herniation Under Falx?
- Aka midline shift hernia
- The most common type of cerebral hernia
- Generally caused by unilateral frontal, parietal, or
temporal lobe disease that creates a mass effect
with medial direction, pushing the ipsilateral
cingulate gyrus down and under the falx cerebri
What is Tentoral Herniation (symmetrical)? Symptoms?
- The movement of brain tissue from one intracranial
compartment to another - Compresses midbrain
- Bilateral dilated pupils
- Coma & tetraparesis
What is Uncal Herniation Over Tentoral? Symptoms?
- Subtype of descending transtentorial herniation
that involves the uncus, caused by raised ICP - Asymmetrical
- Unilateral 3rd nerve palsy
- Tetraparesis
What is Tetraparesis?
A condition in which the patient’s four limbs suffer from muscle weakness
What is Cerebellar Tonsil Herniation?
- Descent of the cerebellar tonsils through the
foramen magnum - This compresses the medulla against the clivus/
odontoid process - Leads to Death
ABCDD
- Airway (catastrophic haemorrhage)
- Breathing
- Circulation
- Disability - baseline observations, pupils, BM, AVPU,
GCS - DontEverForgetGlucose
