Term
| How does Myelography work? |
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Definition
- Interventional procedure where contrast is injected in thecal sac during lumbar puncture.
- Done to distinguish pathology of spinal cord from that of surrounding structures. |
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Term
| How does Angiography work and why is it used in Neurology? |
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Definition
- Catheter inserted into femoral artery and snaked through arterial system into cranial arteries, at which point contrast is injected and CR images are taken.
- Overlying bones are subtracted from image with DSA (6 images per second for flow dynamics).
- Used to evaluate inner lumina of blood vessels |
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Term
| How does PET work and why is it applied by Neurologists. |
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Definition
Functional imaging technique that measures glucose metabolism (tumors metabolize glucose but not scars!).
Poor spatial resolution overcome by PET-CT! |
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Term
| How does Ultrasound work and why is it used in Neurology? |
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Definition
Imaging modality (complicated by presence of bones).
Can be used in pediatric neurology because of fontanelles! |
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Term
When should you use each of the following modalities?
1) CT
2) MR
3) Myelography
4) PET (PET-CT) |
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Definition
1) Screening- cheap and good bone detail
2) Subtle differences in soft tissue- safe and no plane restriction ($$ and in demand!)
3) Bone detail (surgical planning, except for spinal chord or degenerative disease, where MR is used).
4) Source of seizures, tumor vs. scar. PET-CT to stage cancer patients, to evaluate success of therapy to to find hidden primary tumors when metastases are present. |
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Term
| Which neuroradiological modalities utilize contrast? |
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Definition
Some tissues have greater blood supply and take up more of the agent (look for BBB damage as well).
1) Radiodense dyes that block X-rays- CT, CR, Myelography, Angioraphy
2) Paramagnetic agents to distort MF- MRI |
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Term
| What toxicities are associated with use of contrast? |
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Definition
1) Iodinated contrast (CT, Angio, CR, Myelography) is toxic to kidneys (if escapes from chelate) and can cause anaphylaxis if allergic.
2) Patients in heart failures should not be given these agents because it is hyperosmolic (fluid bolus) |
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Term
| How does CT work and why is it used in Neurology? |
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Definition
- Measure differential absorption of X-rays (produced when high-energy electrons bombard metallic surface)
- Bone is set as white and air as black (absorptive properties) |
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Term
How does MR work and why is it used in Neurology?
What is the difference between T1, T2 and FLAIR sequences? |
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Definition
- When H nuclei are subjected to strong MF and then bombarded with radiofrequency pulses, they reflect back characteristic radiofrequency pulse of their own.
- The nature of this pulse depends upon surrounding molecules and on the type of frequency patterns (i.e. T1 vs. T2 gives white vs. dark fat and water is bright on T2, dim on T1 and dark on Flair)
- T1 is useful to clarify anatomy
- FLAIR sequence uses inversion recovery to get rid of free water signal (T2 variant used to detect pathology) |
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Term
| What type of pathology presents as a circumferential small lesion penetrating the BBB (i.e. contrast goes through on CT and MRI) in patients with HIV? |
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Definition
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Term
| Whys is it important to know a patient's age when interpreting their radiological images? |
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Definition
There is a large amount of normal atrophy that occurs in the aging brain, which would be abnormal in a young child (and vice versa).
If you see larger sulci and ventricles in an older patient, don't worry. However, if the Ventricle:sulci ratio becomes very high, you are looking at pathology (probably Hydrocephalus). |
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Term
| Why has catheter-based radiology not been totally replaced by CT or MR-angiography? |
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Definition
Catheters are required for
1) Intervention
2) Small vessel resolution. |
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Term
| Which artery is seen in angiography as coming off of the Carotid siphon? |
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Definition
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Term
| What kind of pathology presents as a lentiform (convex in and out) clot, and how should you respond if you see it? |
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Definition
This is an epidural hemorrhage (since this is a high pressure system, the inner and outer walls are forced to expand, forming the lentiform shape).
Rush to the ER before brain tissue is crushed! |
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Term
| What kind of pathology presents as a Crescentic clot (Convex out and concave in) and how should you respond if you see it? |
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Definition
This sounds like a Subdural hemorrhage.
It is not as dangerous as an epidural hemmorhage, but should be watched closely!
These also occur along the falx cerebelli and tentorium cerebelli. |
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Term
| What kind of pathology presents with finger-like projections into the brain on MRI? |
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Definition
Sounds like a subarachnoid hemhorage, where the subarachnoid is following the pia mater into the gyri and sulci of the brain.
These are likely due to ruptured Aneurysms, where blood is leaking into CSF territory in the ventricles.
They require |
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Term
| What pathology manifests with a high ventricle:sulci enlargement ratio? |
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Definition
This asymmetry is seen in Hydrocephalus and should be distinguished from normal aging (would show symmetrical growth).
You also see "caps" of fluid on the periphery of ventricles |
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Term
| When do you see "straight lines" separating normal and abnormal brain tissue on CT/MRI? |
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Definition
These suggest edema in a region supplied by a singular artery (such of the PCA or the MCA).
It arises because without a glucose supply, Na/K pumps cannot function and Na+ runs into cells, causing them to swell and lyse. |
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Term
| What are watershed infarctions? |
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Definition
| They occur where two arterial systems meet and manifest in a less well-defined manner as singular-supply infarctions. |
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Term
| What are Lacunar infarctions? |
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Definition
| Microvascular occlusions. |
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Term
| A patient presents with a blown left pupil and you rush them to the OR. What could be going on? |
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Definition
Herniation!
Possibly Uncal herniation, where the uncus is forced through the tentorium cerebelli. |
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Term
| Why would you use a CT vs. an MRI and vice versa? |
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Definition
1) MR is better for soft tissue, there is no harmful radiation, it is not restricted to the axial plane, and there are multiple pulse sequences available.
2) CT is cheaper, better at resolving bone and ubiquitous. |
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Term
| Why might you use a Myelography instead of an MRI? |
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Definition
| Better resolution of bone! |
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