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
What does it mean if the pupil is unilaterally dilated and response is sluggish or fixed?
3rd nerve compression secondary to tentorial herniation
What does it mean if the pupils are bilaterally dilated and the response is sluggish or fixed?
- poor CNS perfusion
- bilateral 3rd nerve palsy
What does it mean if the pupils are unilaterally dilated or equal and the response is cross reactive (Marcus-Gunn)?
optic nerve injury
What does it mean if the pupils are bilaterally constricted and the response is difficult to assess?
- opiates
- pontine lesion
- metabolic encephalopathy
What does it mean if the pupils are unilaterally constricted and the response is preserved?
sympathetic pathway disruption
Criteria for immediate CT head:
- GCS <13 on initial
- GCS <15 at 2 hours post injury
- open or depressed fracture
- any sign basal skull fracture (harm-tympanum, panda eyes, CSF leak, Battle’s sign)
- seizure
- focal neuro deficit
- more than 1 episode vomiting
Criteria CT head within 8 hours of injury:
- > =65yo
- history bleeding or clotting disorders
- dangerous mechanism of injury
- more than 30 minutes retrograde amnesia of events immediately before injury
- warfarin
How does an intracerebral haematoma appear on CT?
hyperdense bright lesion
Risk factors intracerebral heamatoma:
- HTN
- vascular lesion
- cerebral amyloid angiopathy
- trauma
- brain tumour or infarct (particularly in stroke patients undergoing thrombolysis)
Symptoms hydrocephalus:
- headache (worse in morning, lying down and during valsalva)
- n&v
- papilloedema
- coma
Hydrocephalus appearance in children:
- skull sutures not fused
- open anterior fontanelle will bulge and become tense
- sunsetting gaze due to compression of superior colliculus in midbrain
What is obstructive hydrocephalus?
- pathology blocking flow
- dilation of ventricles seen superior to site
- tumours, acute haemorrhage, development abnormalities
What is non-obstructive hydrocephalus?
- imbalance of CSF production and absorption
- increased production: choroid plexus tumour)
- failure of reabsorption: meningitis, post-hemorrhagic
What is normal pressure hydrocephalus?
- non-obstructive
- large ventricles but normal pressure
- triad: dementia, incontinence, disturbed gait
Investigations hydrocephalus:
- CT head
- MRI
- lumbar puncture diagnostic and therapeutic
Treatment hydrocephalus:
- external ventricular drain (EVD) in acute, severe hydrocephalus and inserted into right lateral ventricle and drains into bag
- ventriculoperitoneal shunt is long term CSF diversion technique from ventricles to peritoneum
- obstructive: surgical
When must you not use lumbar puncture in hydrocephalus?
- obstructive
- difference in cranial and spinal pressure will cause brain herniation
Causes of spontaneous SAH:
- intracranial aneurysm (85%)
- arteriovenous malformation
- pituitary apoplexy
- arterial dissection
- mycotic aneurysms
- perimesencephalic (idiopathic venous bleed)
Presenting features SAH:
- headache
- n&v
- meningism
- coma
- seizures
- sudden death
- STE on ECG
Confirmation of SAH:
- CT: acute blood is hyper dense on CT typically in basal cisterns, sulci in severe cases, ventricular system
- CT can be negative
- LP: if CT negative, at least 12 hours following onset to allow development of xanthochromia
- normal or raised opening pressure in LP
- referral to neurosurgery asap when confirmed
After spontaneous SAH confirmed, investigations to identify cause:
- CT intracranial angiogram
- digital subtraction angiogram
Treatment SAH:
- most treated with coil
- minority require craniotomy and clipping
- bed rest and well controlled BP
- vasospasm prevented with 21 days of nimodipine (calcium channel inhibitor)
- treat hydrocephalus
Complications SAH:
- re bleeding (10% in first 12 hour)
- vasospasm (7-14 days post)
- hyponatraemia (SIADH)
- seizures
- hydrocephalus
- death
Predictive factors SAH:
- consciousness level
- age
- amount of blood visible on CT
