Neurosurgery Flashcards
Criteria for brain stem death testing:
- deep coma of known aetiology
- reversible causes excluded
- no sedation
- normal electrolytes
Testing for brain death:
- fixed pupils which do not respond to sharp changes of light
- no corneal reflex
- absent oculo-vestibular reflexes - no eye movements following slow injection of at least 50ml of ice cold water into each ear in turn (caloric test)
- no response supraorbital pressure
- no cough reflex to bronchial stimulation or gagging response to pharyngeal stimulation
- no observed respiratory effort
How should the brain death test be undertaken?
- two appropriately experienced doctors on two separate occasions
- both experienced and have at least 5 years post-graduate experience
- on must be consultant
- cannot be member of transplant team if organ donation contemplated
Types of brain herniation:
- subfalcine
- central
- transtentorial/uncal herniation
- tonsillar
- transcalvarial
What is subfalcine herniation?
displacement of cingulate gyrus under falx cerebri
What is central herniation?
downwards displacement of brain
What is transtentorial/uncal herniation?
- displacement of uncut of temporal lobe under tentorium cerebelli
- ispilaterl fixed, dilated pupil
- contalateral paralysis (compression of peduncle)
What is tonsillar herniation?
- cerebellar tonsils through foramen magnum
- ‘coning’
- in raised ICP, compression of cardiorespiratory centre
- chiari malformation
What is transcalvarial herniation?
- when brain is displaced through defect in skull
- fracture or craniotomy site
Where do subdural haematomas most commonly happen and what are the risk factors?
- outermost meningeal layer
- frontal and parietal lobes
- old age and alcoholism
- slower onset than extradural and fluctuating confusion/consciousness
What is diffuse axonal injury?
- mechanical shearing following deceleration
- disruption and tearing of axons
What is secondary brain injury?
- cerebral oedema
- ischemia
- infection
- tonsillar or tentorial herniation
Cushing’s reflex:
- HTN
- bradycardia
Management head injury:
- raised ICP: IV mannitol/furosemide
- diffuse oedema: decompressive craniotomy
- Burr holes and craniotomy flap
- debridement
Who should receive ICP monitoring?
- GCS 3-8 and normal CT
- mandatory if abnormal CT
What is minimum cerebral perfusion pressure in adults and children?
- adults: 70mmHg
- children: 40-70mmHg