Neuroradiology, ICP and CBF, Flashcards
what are common indications for a CT scan in neurology?
- stroke
- headache (subarachnoid haemorrhage)
- tumours
- head trauma
what are contraindications for CT scans in neurology?
- epilepsy
- no significant symptoms post head trauma
what are common indications for MRI scans in neurology?
- CNS tumours
- demyelination
- spine compression (slipped disc)
- epilepsy
- TIA
- headaches
- pediatric neurology
what are contraindications for MRI scans in neurology?
- metallic pacemakers/implants/devices
- claustrophobia/pregnancy/tattoos
what do CT or MRI perfusion scans measure?
amount of blood flowing in volume of tissue in certain amount of time
what indications are cerebral angiograms carried out for in neurology?
- aneurysms
- arteriovenous abnormalities
- carotidocavernous fistula
- persistent epistaxis
what would a CT perfusion scan show in 1. tumours, and 2. stroke?
- increased perfusion - angiogenesis around tumour
2. decreased perfusion - blood vessel blocked or in spasm
what are common indications for PET scans in neurology, and what do they show?
show glucose usage by cells indications: - tumours - inflammation - infection
what are four among the common neurology emergencies which may require imaging?
- head trauma
- stroke
- subarachnoid haemorrhage
- cauda equina syndrome
what is the estimation of cerebral perfusion pressure?
55-60ml/100g/min
what is the volume of cerebral perfusion pressure below which ischaemia occurs?
less than 20ml/100g/min
what is the average volume of a normal brain?
1400g
what is the added volume of blood and CSF to the volume of an average brain?
150mg blood + 150mg CSF
what does cerebral autoregulation consist of?
the ability of maintaining a constant blood flow to brain tissue despite changes in cerebral perfusion pressure changes
above which level of cerebral perfusion pressure is autonomic regulation lost?
150mmHg or above
what equation gives the cerebral perfusion pressure (CPP)?
MAP - ICP
list the three main factors which affect cerebral blood flow
- CPP
- arterial PCO2
- arterial PO2
what are the physiological reactions to low or high CPP in the brain?
low CPP - vasodilation of arterioles to increase blood flow
high CPP - vasoconstriction of arterioles to reduce blood flow
what are the three possible types of cerebral oedema? name a cause for each
- vasogenic (tumour, late stage of infarction)
- cytotoxic (water poisoning, early infarction)
- interstitial (communicating hydrocephalus)
what is the blood brain barrier?
it’s a physical barrier between brain tissue and circulation to keep brain tissue under tight regulation
what is the blood brain barrier made up of?
tight junctions between vascular endothelial cells
tightly packed astrocytes around the brain arterioles
which nutrients can get through the BBB, and through what means?
lipids - passive diffusion
amino acids and sugars - gated channels
what does the Monro-Kellie doctrine explain?
it defines the relative compensation of brain pressure in response to a change in volume
what two concepts does the Monro-Kellie doctrine use? what are the equations for each?
compliance = volume/pressure elastance = pressure/volume
