Brain Imaging Flashcards by Louise Emerson

what is the first line for brain imaging

CT (with/ without contrast)

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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

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do you xray head

never usually

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what are the cistern in the brain

suprasellar and quadrigeminal

CSF spaces

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what will a T1 MRI look like

fluid will be black -good for anatomy and structure

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what will a T2 MRI look like

fluid will be white - good for seeing pathology

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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

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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

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what area is affected by a stroke causing face, leg, arm weakness

parietal lobes- MCA territory

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what area is affected by a stroke causing executive dysfuntion

frontal lobe (ACA, MCA)

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what area is affected by a stroke causing vision problems

posterior circulation - occipital lobe

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how long a window for thrombolysis

4.5-6 hours

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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)

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how do you image acute stroke

non contrast CT

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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)

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what part of brain looses structure fastest when infarcted

insula

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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

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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

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what can white things on a CT brain be

calcium
blood
melanoma mets

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damage to which vessels causes a subdural haemorrhage

bridging veins (blood between dural and arachonoid)

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what colour in blood on unenhanced CT scan

white

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what is intra/extra axial

intra axial- within brain substance

extra axial- outwith brain parenchyma but inside the skull

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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

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

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