Ancillary tests in Neurology (1Q) Flashcards
Preferred imaging to rule out subarachnoid hemorrhage?
CT (no contrast)
Preferred imaging to look for ischmemic or hemorrhagic infarction in brain:
CT or MRI
Preferred imaging to look for mass lesion in brain:
MRI + Contrast
Preferred imaging to look for signs of demyelinating disease in brain:
MRI with or without contrast. Contrast will enhance active lesions.
Imaging used after head trauma:
CT (noncontrast)
Screening used after first seizure with no focal neurologic deficits:
CT, may add contrast
When is MRI preferred to CT in imaging suspected spinal cord lesions?
When focal neurologic defects/signs are present.
What must always be done before administering IV contrast for CT?
Get eGFR and consider alternatives if it is below 30-60. Obv worried about contrast nephropathy.
T1W images are more sensitive to…
subacute hemorrhage and fat-containing structures
T2W images are more sensitive to…
edema, demyelination, infarction, and chronic hemhorrage
FLAIR images are more sensitive to…
water-containing lesions or edema. FLAIR sequence basically suppresses normally intense CSF.
Does Gadolinium contrast cross the BBB?
Very slowly. It is also useful for visualizing lesions in areas that lack a BBB (pituitary, choroid plexus)
Should you worry about reduced renal function in patients receiving gadalinium contrast?
Yes, but less so than with CT contrast. Be cautions if eGFR is <45.
How are perfusion (perfusion MRI) and diffusion (DWI) EPI techniques used?
Used for early detection of ischemic injury of the brain and infarction. Diffusion-weighting shows infarction (low fluid-flow).
Perfusion studies require a bolus of gadolinium contrast and show perfusion problems and be used to assess brain tumors.
Magnetic resonance Neurography
MRN is a T2 weighted MR technique that increases signal of inflamed or irritated peripheral nerves. Useful in radiculopathy that is not seen on conventional MR., or if entrapment suspected.
