1/Kids now out of school? Headache already?? Usually neuroimaging doesn’t add much in headaches, but in occipital neuralgia MR neurography can add a lot.
2/ There are actually 3 occipital nerves:greater, lesser and least. They arise from the upper cervical nerves and innervate various areas of the dorsal scalp. The greater occipital nerve is the only one large enough to image and it arises from C2
3/The greater occipital nerve is the largest cutaneous nerve in the body and can be traced from its origin at the dorsal ramus of C2 along the scalp in MR neurography
4/Many pathologies can affect the greater occipital nerve, but most commonly, it is compression between muscles, resulting in occipital neuralgia. This is the basis behind Botox treatment for occipital neuralgia. Decompressive surgery can also be used to provide relief
5/Where is it compressed? Usually between the multifidus and semispinalis capitis. We can use MR neurography to rule out other pathologies of the nerve and confirm compressive injury
6/MR neurography can confirm unilateral dz preop or post op neuromas w/persistent pain. This is a pt w/unilateral right dz w/a brighter larger right nerve, indicating Sunderland 1 injury from compression
Not all headaches have to be a diagnostic headache with MR neurography 😉
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Brain MRI anatomy is best understood in terms of both form & function.
Here’s a short thread to help you to remember important functional brain anatomy--so you truly can clinically correlate!
2/Let’s start at the top. At the vertex is the superior frontal gyrus. This is easy to remember, bc it’s at the top—and being at the top is superior. It’s like the superior king at the top of the vertex.
3/It is also easy to recognize on imaging. It looks like a big thumb pointing straight up out of the brain. I always look for that thumbs up when I am looking for the superior frontal gyrus (SFG)
@TheAJNR 2/Everyone knows about the spot sign for intracranial hemorrhage
It’s when arterial contrast is seen within a hematoma on CTA, indicating active
extravasation of contrast into the hematoma.
But what if you want to know before the CTA?
@TheAJNR 3/Turns out there are non-contrast head CT signs that a hematoma may expand that perform similarly to the spot sign—and together can be very accurate.
1/My hardest thread yet! Are you up for the challenge?
How stroke perfusion imaging works!
Ever wonder why it’s Tmax & not Tmin?
Do you not question & let RAPID read the perfusion for you? Not anymore!
2/Perfusion imaging is based on one principle: When you inject CT or MR intravenous contrast, the contrast flows w/blood & so contrast can be a surrogate marker for blood.
This is key, b/c we can track contrast—it changes CT density or MR signal so we can see where it goes.
3/So if we can track how contrast gets to the tissue (by changes in CT density or MR signal), then we can approximate how BLOOD is getting to the tissue.
And how much blood is getting to the tissue is what perfusion imaging is all about.