Head injury Flashcards
What is primary brain injury?
This is when sudden acceleration, deceleration or rotation causes the brain to move so much in the skull that causes:
Tearing of nerve fibres Petechial haemorrhages within the white matter Contusions and lacerations of the cortex
Secondary brain injury is when the initial head injury causes the brain to be diffusely damaged and therefore vulnerable to 4 other insults - what are these?
-what do all four of these cause?
Arterial hypotension:
- From blood loss at the time of injury: scalp/elsewhere in body
- Hypotension and/or hypoxia can cause hypoxic-ischaemic brain damage with swelling
Arterial hypoxia:
-Due to airway obstruction/assoc. chest injury/epileptic fit
Infection:
- Head injuries by which skull fracture has occurred can allow organisms to enter the skull
- Infection causes inflammatory oedema
Intracranial haematoma:
-Force of injury may have torn a vessel inside the skull = haematoma
-Either in brain substance or meninges
= compression
These all cause further brain swelling and encourage downward cascade to brainstem failure and death
describe the pathophysiology of primary brain injury and how this can allow secondary brain injury
The release of excitatory amino-acids (glutamate/aspartate) bind to receptors (e.g.NMDA)
This causes the release of intracellular calcium and the activation of phospholipases This leads to the breakdown of cell membranes, cell swelling and activation of apoptosis
This leads to secondary brain injury from:
Loss of blood-brain-barrier Leucocyte infiltration = inflammation Loss of cerebral autoregulation of blood pressure = ischaemia Loss of cerebral autoregulation of blood flow = metabolic decoupling = even more ischaemia causing further brain oedema
What is cerebral perfusion pressure? what CPP is aimed for after brain injury?
CPP = MAP - ICP
Hypotension has a major influence on CPP Aim for CPP of > 60mmHg after head injury ie MAP > 80mmHg and keeping ICP < 20mmHg Normal adult ICP is 9-11mmHg (12 -15 cm H2O)
What clinical features are seen in a skull base fracture?
haematoma over mastoid (battle sign) – middle cranial fossa
bilateral periorbital haematoma (panda eyes) – anterior cranial fossa Subconjuctiva haematoma – blood under conjunctiva with no posterior margin indicating blood tracking forward from orbit CSF discharge from nose or ear (clear fluid) Bleedng from ear
When should a CT head be performed immediately after a brain injury?
GCS < 13 on initial assessment
GCS < 15 at 2 hours post-injury
suspected open or depressed skull fracture.
any sign of basal skull fracture (haemotympanum, ‘panda’ eyes, cerebrospinal fluid leakage from the ear or nose, Battle’s sign).
post-traumatic seizure.
focal neurological deficit.
more than 1 episode of vomiting
Taking anti-coagulants
When should a CT scan be perfomed within 8 hours of injury?
for adults with any of the following risk factors who have experienced some loss of consciousness or amnesia since the injury:
- age 65 years or older
- any history of bleeding or clotting disorders
- dangerous mechanism of injury (a pedestrian or cyclist struck by a motor vehicle, an occupant ejected from a motor vehicle or a fall from a height of greater than 1 metre or 5 stairs)
- more than 30 minutes’ retrograde amnesia of events immediately before the head injury
What methods of cerebral protection exist following brain injury?
CSF Drainage-reduces ICP
Mannitol -improves micro-perfusion
Hypertonic saline-may be better than mannitol
Hyperventilation-temporary effect (2-4 hrs)
Hypothermia -weak evidence for effect
Decompressive craniectomy – randomised trial underway
Describe the mechanism of injury and clinical features of an extradural haematoma?
Bleeding into the space between the dura mater and the skull. Often results from acceleration-deceleration trauma or a blow to the side of the head. The majority of epidural haematomas occur in the temporal region where skull fractures cause a rupture of the middle meningeal artery.
Features
features of raised intracranial pressure some patients may exhibit a lucid interval
What does an extradural haematoma look like on CT?
Convex shaped - skulls sutures where dura mater is attached to the skull constricts the haematoma
Describe the mechanism of injury and clinical features of a subdural haematoma?
Bleeding into the outermost meningeal layer. Most commonly occur around the frontal and parietal lobes.
due to stretching and tearing of bridging cortical veins as they cross the subdural space to drain into an adjacent dural sinus.
Risk factors include old age, alcoholism and anticoagulation.
Slower onset of symptoms than a epidural haematoma.
Describe the appearance of subdural haematoma on CT?
lens shaped
What is the mechanisms of injury and clinical features of a subarachnoid haemorrhage?
Usually occurs spontaneously in the context of a ruptured cerebral aneurysm but may be seen in association with other injuries when a patient has sustained a traumatic brain injury
What is the cushings reflex and is this an early or late sign of brain injury?
the Cushings reflex (hypertension and bradycardia) often occurs late and is usually a pre terminal event
SAH - what is the presentation
Sudden onset severe headache Collapse Vomiting Neck pain Photophobia
