Neuro Other Flashcards
(23 cards)
What is first choice imaging for ENT?
CT
What imaging modality may be used in the setting of trauma and is commonly used regarding degenerative issues of the spine?
radiography
the selection of what shades of gray in an examination are viewed on the computer monitor at any one time is called…
windowing
radiographic densities on a CT are described as attenuation and different attenuations are measured in what units?
Hounsfield units
What has a Hounsfield unit of 0?
water
Average of brain tissue in Hounsfield units would be about what?
+35
In the body, on one CT, what could the span of Hounsfield units be?
2000 units - potentially 2000 shades of gray
How many shades of gray can the human eye detect?
20-70 shades
What four windows do we most often use when interpreting a head CT?
- brain window
- bone window
- blood or subdural window
- soft tissue window
The window level selected is usually…
the middle value from the Hounsfield units that the tissue you want to see, has
The width of the window you select needs to be…
wide enough to include all of the Hounsfield units that that particular tissue may have
All tissues with Hounsfield units lower than what is included in your window will appear…
black
A subdural window is ideal for observing…
a subdural hematoma, but would probably obseer most any intracranial hemorrhage.
Generally, does grey or white matter have more attenuation? Why?
grey has greater attenuation because it has more blood and less myelin
cytotoxic edema is normally thought of in ischemia and acute stroke. On the cellular physiology level, what is happening?
What is seen on CT?
ATP Na-K pump can no longer function so Na increases inside the cell, drawing in extracellular water, causing the cell to swell
on CT as a loss of the grey-white distinction
What is the main difference between cytotoxic edema and vasogenic edema?
cytotoxic edema has the BBB still intact and in vasogenic edema, BBB is not intact
How can you tell the difference on CT of vasogenic edema v cytotoxic edema?
cytotoxic edema - grey matter becomes less attenuated, becoming more like white and losing the grey white junction
vasogenic edema - attenuation of white matter goes down, making the grey white junction exaggerated
intra-axial means that the location of something is…
within the spinal cord or brain
What does an epidural hematoma look like? What kind of bleed usually causes it?
lens shape or biconvex
does not cross suture lines
usually arterial bleed, such as middle meningeal artery
pt is younger, has had head trauma, and might have skull fx, what kind of bleed?
epidural hematoma
pt is older, may or may not have known trauma, pt has a …
subdural hematoma
What shape is a subdural hematoma? What kind of bleed is it usually from? Can they cross suture lines?
cresecent
venous, subdural vein bleed
can cross suture lines
What kind of bleed may be spontaneous, from a ruptured cerebral aneurysm?
subarachnoid hemorrhage
