9/23 Neuroimaging II Flashcards
planes
coronal: anterior/posterior
sagittal: left/right
transverse/axial/horizontal: superior/inferior or cranial caudal
recap: main use of FLAIR
similar to T2W BUT CSF is hypointense → good for viewing demyelination around ventricles in multiple sclerosis
T1W vs T2W vs FLAIR vs DWI
terminology
diffs/uses
hyper/iso/hypoINTENSITY
T1W:
water/csf (hypo) < edema < gray matter (iso) < white matter (myelin = fat) (hyper)
T2W:
white matter (hypo) < gray matter (iso) < edema < water/csf (hyper)
FLAIR: fluid attenuation inversion recovery → pathology (MS)
similar to T2W except csf is hypointense
- good for eval of white matter adj to ventricles!
DWI: diffusion weighted image
primary seq for detection of acute/subacute infarcts up to 14d old → STROKES
- hyperintense signal = abnormal
blood products on CT
- hyperacute
- acute
- early subacute
- late subacute
- chronic
why change in signals?
stage → CT signal → time
hyperacute → high → under 6hr
acute → high → 8-72hr
early subacute → high → 3d-1wk
late subacute → isodense → 1wk-1mo
chronic → low → 1mo+
changes in density due to changes in Hb and types
summary: blood on CT starts off bright, then becomes darker
- changes start around 3d point
why might you see mixed types of blood in subdural hematoma?
subdural hematoma: usually due to tearing of bridging veins
- blood oozes out slowly
- older blood will show up isodense
- newer blood will show up hyperdense
characteristics of epidural hematoma
usually lens shaped, hyperdense (bc brain cant accomodate it the same way it might in gyri/sulci so sx become apparent/debilitating sooner)
characteristics of subarachnoid hematoma
“worst headache of life” presentation
- want to do a LP just in case you miss blood on CT
often from trauma or aneurysm
infiltrative oligodendroglioma
high signal in pons
infiltrative tumor of brainstem
optic chiasm glioma
suprasellar cistern looks huge
actually seeing a tumor of the optic chiasm
Chiari I malformation
hindbrain malformation
- cerebellar tonsillar herniation through foramen magnum
- blocks csf flow → syrinx in cervical cord → headaches in young patients
neurofibromatosis spots in globus pallidi
skin lesions and brain lesions simultaneously
- cafe au lait spots & multiple neurofibromas
prone to tumors (esp intracranial)
globus pallidus preferentially affected
pineal gland germinoma
tumor of pineal gland → pushes down on tectum (roof of 4th ventricle) → blocks flow of CSF, causing hydrocephalus
can also extend into thalamus and 3rd ventricle
pericallosal lipoma
curvilinear fatty structure above corpus callosum
present with devpt delay, incoordination, vague symptoms bc can inhibit formation of corpus callosum
can see dark fluid where body/splenium should be bc devpt of corpus callosum was inhibited
Alexander’s disease
- inborn error of metabolism
- dismyelinating disease
- present with enlarged heads, seizure, spasticity, incoordination
MRI shows tons of abnormal white matter
- disease preferentially affects white matter
vestibular Schwannoma
occurs in internal auditory canal (CN VIII)
- potential deformation of fourth ventricle
present with hearing loss
want to get an MRI!!! bc cant see with CT
