Cerebral Perfusion and Intracranial Pressure Flashcards
what is vasogenic oedema?
when there is disruption of the blood brain barrier
what oedema is caused by membrane failure?
cytotoxic oedema influx of Ca creating cellular swelling
what are some secondary effects of raised ICP?
> herniation syndromes
> decreased cerebral perfusion
what is the munro kellie doctrine?
(brain + blood + CSF) volume = intracranial space. this must remain constant
in the adult brain how much of the cardiac output does the brain receive?
15%
what is the myogenic mechanism?
auto-regulation where vascular smooth muscle constricts in response to an increase in wall tension
what does a subfalcine herniation affect?
medial motor cortex
what may an uncal herniation affect?
> CN 3
ipsilateral corticospinal tracts
what sort of herniation would cause brain stem damage?
foramen magnum herniation
what management may a patient with raised ICP receive in ITU?
> 30 degree head position > no impediment of venous drainage > CO2 maintained below normal range > intermittent boluses of mannitol when ICP raised > fully sedated and paralysed
what surgical interventions can be carried out to reduced inter-cranial pressure?
> craniotomy and evacuation of clot
external ventricular drainage
decompressive craniectomy
list some common indications to perform a CT scan
> Head trauma > acute stroke > headache (sub arachnoid haemorrhage) > cancer > post surgical
what would indicate a MRI?
> demyelination > CNS tumours > suspected disc prolapse > TIA > epilepsy > paediatric neurology > headache > cancers
state some contraindications to perform a MRI
> cardiac pacemakers/cochlear implants
programmable shunts/insulin pumps (relative)
moveable metallic implants
for what can angiography be used?
diagnosis and treatment of vascular abnormalities: > aneurysm > arteriovenous malformation > carotidocavernous fistula > unstoppable epistaxis
define perfusion
the volume of blood passing through a defined volume of tissue per unit time
what are the units in CT perfusion?
ml blood/ 100g tissue/ min
name a disorder where there would be decreased perfusion
stroke
name a disorder where there would be increased cerebral perfusion
tumour: angiogenesis and a more aggressive tumour
what does PET scan map out?
glucose usage
where can increased metabolism be seen?
> tumour
inflammation
infection
in a CT is bone white?
yes
what type of MRI has white CSF?
T2
what colour is skull on an MRI?
black
what are the advantages of a plain radiograph?
> universal availability
fast
sequential images in subtraction angiography
what is the disadvantage of a plain radiograph?
lacks soft tissue detail
what are the advantages of ultrasound?
> no radiation
less expensive
movement tolerant
what are the disadvantages of ultrasound?
> requires a wide enough open frontanelle
> quality and interpretation is based on the operator
what are the advantages of a CT scan?
> rapid
metal tolerant
good at acute haemorrhage
what are the disadvantages of the CT scan?
> radiation 2mSv
> expensive and cumbersome equipment
what physiological information can radionuclide radiology give?
> glucose metabolism
perfusion
dopamine reuptake receptors
what are the disadvantages of radionuclide radiology?
> unclear anatomical information
> radiotracers can be expensive
what are the advantages of the MRI?
> no radiation
soft tissue differentiation
physiological information: blood flow, diffusion restriction and metabolite concentrations
give some disadvantages of MRI
> poor metal tolerance > electronics > little movement tolerance > slow > expensive > metal can become projectiles
