Neurosurgery Flashcards
Criteria for brain stem death testing
Deep coma of known aetiology
Reversible causes excluded
No sedation
Normal electrolytes
Testing for brain death should be undertaken by whom?
two appropriately experienced doctors on two separate occasions
other should be experienced in performing brain stem death testing and have at least 5 years post-graduate experience. One of them must be a consultant.
members of transplant team cannot confirm brain stem death
true
Testing for brain death - eyes
Fixed pupils which do not respond to sharp changes in the intensity of incident light
No corneal reflex
Absent oculo-vestibular reflexes
No response to supraorbital pressure
Testing for brain death - breathing/pharynx
No cough reflex to bronchial stimulation or gagging response to pharyngeal stimulation
No observed respiratory effort in response to disconnection of the ventilator
oculo-vestibular reflexes are tested how?
slow injection of at least 50ml of ice-cold water into each ear in turn (the caloric test)
- no eye movements = absent reflexes
Describe the following type of herniation: Subfalcine
Displacement of the cingulate gyrus under the falx cerebri
Describe the following type of herniation: Central
Downwards displacement of the brain
Describe the following type of herniation: Transtentorial / uncal herniation
Displacement of the uncus of the temporal lobe under the tentorium cerebelli.
Describe the clinical consequences of uncal/transtentorial herniation
parasympathetic compression of the third cranial nerve - ipsilateral dilated pupil
ompression of the cerebral peduncle - contralateral paralysis
Describe the following type of herniation: Tonsillar
Displacement of the cerebellar tonsils through the foramen magnum
Tonsillar herniation is also called coning
true
tonsillar herniation/coning in raised ICP results in?
compression of the cardiorespiratory centre
tonsillar herniation/coning in chiari 1 malformation is seen without raised ICP
true
Describe the following type of herniation: Transcalvarial
Occurs when brain is displaced through a defect in the skull (e.g. a fracture or craniotomy site)
The brain autoregulates its blood supply
true
as ICP rises you get increasingly hypotensive systemically
false
systemic circulation will display changes to try and meet the perfusion needs of the brain. Usually this will involve hypertension.
if ICP compresses the brain what are the consequences?
cranial nerve palsies
compression of essential centres in the brain stem will occur. When the cardiac centre is involved bradycardia will often develop.
Extradural haematoma Often results from
acceleration-deceleration trauma or a blow to the side of the head
The majority of extradural haematomas occur where?
The majority of extradural haematomas occur in the temporal region where skull fractures cause a rupture of the middle meningeal artery.
Extradural haematoma may have a lucid interval
true
Subdural haematoma Most commonly occur around the
frontal and parietal lobes
subdural has a slower/faster onset of symptoms compared to extrafural haematoma
slower
Subarachnoid haemorrhage Usually occurs spontaneously in the context of
ruptured cerebral aneurysm, but may be seen in association with other injuries when a patient has sustained a traumatic brain injury.
Pathophysiology of haematoma?
Primary brain injury may be focal (contusion/ haematoma) or diffuse (diffuse axonal injury)
Diffuse axonal injury occurs as a result of mechanical shearing following deceleration, causing disruption and tearing of axons
Intra-cranial haematomas can be extradural, subdural or intracerebral, while contusions may occur adjacent to (coup) or contralateral (contre-coup) to the side of impact
Secondary brain injury occurs when cerebral oedema, ischaemia, infection, tonsillar or tentorial herniation exacerbates the original injury. The normal cerebral auto regulatory processes are disrupted following trauma rendering the brain more susceptible to blood flow changes and hypoxia
The Cushings reflex (hypertension and bradycardia) often occurs late and is usually a pre terminal event
Where there is life threatening rising ICP such as in extradural haematoma and whilst theatre is prepared or transfer arranged use of IV ? may be required.
mannitol/ frusemide
Diffuse cerebral oedema may require
decompressive craniotomy
in head injury Hyponatraemia is most likely to be due to the syndrome of inappropriate ADH secretion.
true