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.
What are PET scans most useful for?
Picking up regional changes in glucose activity, including in Alzheimer’s and when looking for extracranial metastatic disease.