Brain Imaging Flashcards
what is the first line for brain imaging
CT (with/ without contrast)
what are pros and cons for MRI brain
better soft tissue resolution grey and white matter differentiation more obvious than CT longer duration CI in some with/without contrast
do you xray head
never usually
what are the cistern in the brain
suprasellar and quadrigeminal
CSF spaces
what will a T1 MRI look like
fluid will be black -good for anatomy and structure
what will a T2 MRI look like
fluid will be white - good for seeing pathology
what does interruption of blood flow in an intracranial artery lead do
deprivation of oxygen and glucose
this initiates a cascade which if not stopped causes cell death via liquid factor necrosis
what are the causes of ischaemic stroke
embolism- cardiac (AF, ventricular aneurysm, endocarditis), paradoxical (patent foramen ovale), atherosclerotic, fat, embolism, air
thrombosis (clot)- perforator (lacunar infarct), acute plaque rupture with overlying thrombosis
arterial dissection
what area is affected by a stroke causing face, leg, arm weakness
parietal lobes- MCA territory
what area is affected by a stroke causing executive dysfuntion
frontal lobe (ACA, MCA)
what area is affected by a stroke causing vision problems
posterior circulation - occipital lobe
how long a window for thrombolysis
4.5-6 hours
why do you image the brain in acute stroke
exclude intracranial haemorrhage
confirm ischaemia
exclude stroke mimics (e.g tumour)
permit rapid treatment (thrombolysis/ mechanical thrombectomy)
how do you image acute stroke
non contrast CT
what is the early signs of an ischaemic stroke on CT
hyperdense segment of a vessel (wedge shape)
direct visualisation of the intravascular thrombus/ embolus (the clot in the vessel)
what part of brain looses structure fastest when infarcted
insula
what is seen on CT a few hours after an ischaemic stroke
loss of grey/ white matter differentiation, hypoattenuation (become less dense) of deep nuclei
cortical hypodensity with associated parenchymal swelling with resultant gyral effacement (loss of structure)
with time the hypoattenutation and swelling become more marked resulting in a significant mass effect- midline shift
what is gliosis, when does it happen and what does it look like on CT
due to liquid factor necrosis
happens following ischaemia (stroke)
appears as a region of low density with volume loss
what can white things on a CT brain be
calcium
blood
melanoma mets
damage to which vessels causes a subdural haemorrhage
bridging veins (blood between dural and arachonoid)
what colour in blood on unenhanced CT scan
white
what is intra/extra axial
intra axial- within brain substance
extra axial- outwith brain parenchyma but inside the skull
what are the subdivision of extra axial haemorrhages
extra dural (between skull and outer layer of dura mater)
subdural (between dura and arachnoid- with CSF)
subarachonoid (will follow sulci and gyri)
what is the typical appearance of a hypertensive bleed
acute haematoma in the basal ganglia (thalamus)
what are extra dural haemorrhages associated with
trauma, often have associated skull fracture
what vessels is usually damaged in an extra dural haemorrhage
usually arterial- commonly the middle meningeal artery
what shape is an extradural haemorrhage
biconvex
can cause mass effect with midline shift, herniation and sulcal effacement
limited by cranial sutures
what usually causes a subdural haemorrhage
can happen at any age- usually due to head trauma
infants- NAI
young adults- RTA
elderly- falls
what does a subdural haemorrhage look like
semilunar shape
crosses sutures
doesnt cross midline
can cause mass effect
what causes an acute on chronic subdural haematoma
people who are anticoagulated- repeated falls
how does a subdural evolve on CT from subacute to chornic
subacute brain will be isodense
chronic will be hypodense
what does an acute on chronic subdural haemorrhage look like
will see fluid level of acute blood adjacent to more chronic collection
is subarachnoid haemorrhage intra or extra axial
extra axial (blood within the subarachnoid space not within the parechyma)
what does a subarachnoid haemorrhage look like
hyperdense material commonly around the circle of willis can also go into cistern, fissures, sulci stellate sign (star)
what are subarachnoid haemorrhages associated with
85% berry aneurysm
can be traumatic/ related to other vascular malformations
what is done when a subarachoid haemorrhage is found in the asbence of trauma
CT cerebral angiography is performed
what do most people die of who have a subarachonid haemorrhage
hydrocephalus -> vasospasm -> infarction
what cancers commonly metastasise to the brain
lung, breast, melanoma, renal cell, colorectal
what are the majority of brain tumours in adults
mets
primary brain tumours more common in children
what is usually the first test for an intracranial mass
CT
what does hypo and hyper dense CT mean
hypo dense= black
hyper dense= whitw
what can contrast be used for in intracranial masses
can make lesions more conspicuous - depends on integrity of blood brain barrier
what do brain mets usually look like
usually mutliple
supra or infra tentorial
lots of oedema and mass effect
avidly enhance
what do primary brain tumours usually look like on CT
usually solitary
supra or infra tentorial
degree of oedema, mass effect and enhancement depends on grade
describe tonsilar herniation (coning)
descent of the cerebral tonsils below the foramen magnum
brainstem is compressed against the clivus - altering the vital life sustaining function of the pons and medulla
what is the spinal cord in
within spinal canal of vertebral column, within thecal sac
where is the conus medullaris
L1
what is the treatment for spinal cord compression
is a surgical emergency
prompt decompression to prevent neurological damage
what can cause spinal cord compression
intervertebral disc: disc protrusion, disc extrusion, discitis, osteomyelitis vertebral: trauma, tumour epidural space: adscess, haematoma dura: spinal meningioma intradural space: nerve sheath tumour
what are the red flags for back pain
Hx of malignancy
major trauma
thoracic/ radicular pain
constant, progressive, non mechanical pain
systemically unwell
widespread neurological signs and symptoms
urinary retention, saddle anaesthesia
what Ix for spinal cord compression
MRI spine
what does a retropulsed vertebrae mean
has been pushed backwards
what is used for thrombolysis in stroke
alteplase
when would you not thrombolyse
if patient heavily anticoagulated e.g. on warfarin
careful in Hx of previous infarct (likely to bleed)
what is seen on CT a long time after a stroke
scarring- gliosis, volume loss, ex vacuolar dilation
