Disability Flashcards
What are examples of primary head injuries?
- Skull fractures
- Focal brain injuries
- Contusions
- Extradural haematomas
- Diffuse brain injury
What are examples of secondary head injuries?
- Hypercapnia
- Hypoxia
- Hyper/hypoglycaemia
If someone is hypotensive, how does this have an impact on cerebral perfusion in someone with increased ICP?
ICP needs to rise less to decrease CPP - Moratlity is twice that of normotensive patients
What is the Munro-Kellie Doctrine?
States that the cranial compartment is incompressible and that the volume inside the cranium is fixed. The cranium and its constituents (blood, CSF, and brain tissue) create a state of volume equilibrium, such that any increase in volume of one of the cranial constituents must be compensated by a decrease in volume of another.
Vcsf+Vblood+Vbrain+Vother = Vintracranial space = constant
How would you calculate cerebral perfusion pressure?
CPP = MAP - ICP
How do you calculate mean arterial pressure?
Diastolic BP + 1/3 pulse pressure
What are signs of raised ICP?
- Abnormal posturing
- Decreased consciousness level
- Vomiting - due to vomit centre compression
- Headache
- CN III palsy
- CN VI palsy
What are late features of raised ICP?
Cushing’s triad:
- Hypertension
- Bradycardia
- Irregular breathing
How would you assess disability?
- AVPU/GCS
- Pupillary size/symmetry/reaction
- Blood glucose
- Signs of base of skull fracture
- Focused neuro exam
Why do individuals with raised ICP develop bradycardia as a late sign?
As part of Cushing’s Triad/Reflex:
- Increase in systolic and pulse pressure
- Bradycardia
- Irregular respiration
Baroreceptors in the aortic arch detect the initial increase in blood pressure and trigger a parasympathetic response - induces bradycardia, which signifies the second stage of the reflex
Why do those raised ICP develop Hypertension as a late sign?
As part of Cushing’s Reflex
- Disturbed repiratory pattern
- Bradycardia
- Hypertension
In response to raised ICP, the body attempt to restore adequate perfusion to the ischaemic brain, as raised ICP reduces flow of blood into the brain
Why can those with raised ICP develop irregular/depressed breathing?
As part of Cushing’s Reflex
- Disturbed repiratory pattern
- Bradycardia
- Hypertension
Distortion and/or increased pressure on the brainstem causes an irregular respiratory pattern and/or apnea
What are the different criteria for an eye score in GCS?
- 4 - opens voluntarily
- 3 - opens to voice
- 2 - opens eyes to pain
- 1 - does not open eyes
What are the different criteria for the verbal scoring of GCS?
- 5 - Speaking normally
- 4 - confused
- 3 - abnormal words/ incomplete sentences
- 2 - mumbling/noises
- 1 - no sound
What are the criteria for scoring the motor score for GCS?
- 6 - following commands
- 5 - localising to pain
- 4 - normal flexing to pain
- 3 - Abnormal (decorticate) flexion to pain
- 2 - Abnormal (decerebrate) extension to pain
- 1 - No movement
What are the components to decroticate posturing?
- Facilitation of the rubrospinal tract and medullary reticulospinal tracts - leads to biased flexion of upper extremities as tone from these tracts outweighs the medial and lateral vestibulospinal and pontine reticulospinal tract which facilitates extension in the upper extremities.
- Disruption of lateral corticospinal tract - reduces motor neuron activity in the lower spinal cord supplying flexor muscles of the lower extremities. The pontine reticulospinal and the medial and lateral vestibulospinal biased extension tracts greatly overwhelm the medullary reticulospinal biased flexion tract.
The effects on these two tracts (disruption of corticospinal and facilitation of rubrospinal) by lesions above the red nucleus is what leads to the characteristic flexion posturing of the upper extremities and extensor posturing of the lower extremities.
Why does decerebrate posturing occur?
Lesions below the red nucleus cause disruption of supply to flexors. However, vestibulospinal tracts are unaffected, meaning that extensors predominate. This leads to the arms and legs being extended and rotated internally. The patient is rigid, with the teeth clenched.
What does decorticate posturing indicate?
There may be damage to areas including the cerebral hemispheres, the internal capsule, and the thalamus. It may also indicate damage to the midbrain
Where is the red nucleus?
Located in the tegmentum of the midbrain next to the substantia nigra and comprises caudal magnocellular and rostral parvocellular components
What does decerebrate postuing indicate?
Indicates brain stem damage, specifically damage below the level of the red nucleus (e.g. mid-collicular lesion). It is exhibited by people with lesions or compression in the midbrain and lesions in the cerebellum, and is commonly seen in pontine strokes
What does progression from decorticate to decrerebrate posturing indicate?
Progression from decorticate to decerebrate posturing is often indicative of uncal (transtentorial) or tonsilar brain herniation
What are signs of a base of skull fracture?
- Battle’s sign – bruising of the mastoid process of the temporal bone.
- Raccoon eyes – bruising around the eyes, i.e. “black eyes”
- CSF rhinorrhea
- CSF otorrhoea
- Cranial nerve palsy
- Bleeding (sometimes profuse) from the nose and ears
- Hemotympanum
What is regarded as a severe head injury based on GCS scoring?
<8
What would be regarded as a moderate head injury based on GCS score?
9-12
What would be regarded as a mild head injury based on GCS scoring?
13-15
What methods can be used to elicit pain in someone to assess response to pain?
- Pressure on nail bed with pencil
- Supraorbital pressure
- Jaw angle pressure
- Sternal rub
When is a patient regarded as being comatose?
GCS < 8
What do you want to assess when looking at someones pupils?
- Size
- Shape
- Equal/unequal
- Response to light
What can a unilateral fixed dilated pupil indicate?
Brainstem compression/impending herniation - due to compression of CN III
If someone had a fixed, dilated pupil, what would this indicate in terms of prognosis?
Catastrophic sign of oculomotor nerve compression due to uncal herniation. When present, mortality approaches 100% without emergent medical intervention and surgical decompression
What is Hutchison’s pupil?
Hutchinson’s pupil is a non-reactive dilated pupil caused by oculomotor nerve compression secondary to uncal herniation. Other signs of oculomotor nerve palsy (e.g. extraocular muscle weakness, ptosis) may also be present
What is the cause of a fixed dilated pupil?
Uncal herniation - results from an expanding extra-axial intracranial haematoma or mass. Increasing intracranial volume pressure result in cerebral herniation when the expanding intracranial contents (e.g. a mass) exceed the capacity of the cerebral tissue and intracranial contents to accommodate such a change.
Cerebral tissue moves in the direction of the pressure gradient (i.e. caudally towards the foramen magnum). Herniation of the medial temporal lobe and uncus may result in compression of the midbrain and oculomotor nerve, resulting in a non-reactive dilated pupil
What are focal brain injuries?
These occur at a specific site in the brain and include extradural, subdural heamatomas and parenchymal contusions.
What is diffuse axonal injury?
Due to fixation of axons to the skull base and other structures the
acceleration and deceleration leads to diffuse shearing forces transmitted throughout the axons in the brain. Under severe strain maximum elasticity of the axons is overwhelmed, causing widespread damage.
What general measures can you take pre-hospitally to manage someone with a head injury?
- Maintain patient at 30o of head elevation
- Protect airway - consider intubation/ventilation
- Two large bore IV cannulas - control hypovolaemia with fluids
-
Continuous assessment
- Pulse oximetry
- BP
- Ensure Adequate paraemters for transfer - normotensive, normoxia, normoglycaemia
What do you need to be careful of when using analgesia in the context of head injury?
Try to avoid hypotensive effects
What should you always consider testing in someone with reduced consiousness?
Blood glucose
How would you manage hypoglycaemia?
- 15-20g simple carbs - lucozade/jelly beans
- IM glucagon
- IV glucose
What is haemotypanum?
Presence of blood in the tyympanic cavity, if the eardrum has ruptured then this could be seen as bloody discharge from the ears
What is the following, and what might it indicate?
Haemotympanum - base of skull fracture
What is the following, and what might this indicate?
Battle’s sign - indicative of base of skull fracture
What is the following, and what is it indicative of?
Racoon sign - Base of skull fracture
How do focal brain injuries occur?
Produced by collision to the skull, leading to compression of the tissue underneath the site called a coup injury, or the tissue opposite the site called a countercoup injury. These occur with sudden deceleration forces, such as in a car accident
What cranial nerve controls the pupillary sphincter muscles?
Cranial nerve III - parasympathetic fibres
What nerves control dilator muscles in the pupil?
Post-synaptic neurons of the superior cervical ganglion - sympathetic control
What is the mainstay of management with a neurologically compromised patient in a pre-hospital setting?
Stabilisation and transfer
What is the general physiological outcome of diffuse axonal injury?
Oedema, causing raised the ICP and leading to death or further secondary injury.
