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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/074/a_image_thumb.png?1474760408)
optic chiasm glioma
suprasellar cistern looks huge
actually seeing a tumor of the optic chiasm
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/226/a_image_thumb.png?1474760642)
Chiari I malformation
hindbrain malformation
- cerebellar tonsillar herniation through foramen magnum
- blocks csf flow → syrinx in cervical cord → headaches in young patients
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/337/a_image_thumb.png?1474760809)
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/427/a_image_thumb.png?1474760838)
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/533/a_image_thumb.png?1474760980)
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/604/a_image_thumb.png?1474761160)
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/754/a_image_thumb.png?1474761350)
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/197/341/791/a_image_thumb.png?1474761603)