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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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.
1/”That’s a ninja turtle looking at me!” I exclaimed. My fellow rolled his eyes at me, “Why do I feel I’m going to see this a thread on this soon…”
He was right! A thread about one of my favorite imaging findings & pathology behind it
2/Now the ninja turtle isn’t an actual sign—yet!
But I am hoping to make it go viral as one. To understand what this ninja turtle is, you have to know the anatomy.
I have always thought the medulla looks like a 3 leaf clover in this region.
The most medial bump of the clover is the medullary pyramid (motor fibers).
Next to it is the inferior olivary nucleus (ION), & finally, the last largest leaf is the inferior cerebellar peduncle.
Now you can see that the ninja turtle eyes correspond to the ION.
3/But why are IONs large & bright in our ninja turtle?
This is hypertrophic olivary degeneration.
It is how ION degenerates when input to it is disrupted. Input to ION comes from a circuit called the triangle of Guillain & Mollaret—which sounds like a fine French wine label!
1/I always say you can tell a bad read on a spine MR if it doesn’t talk about lateral recesses.
What will I think when I see your read? Do you rate lateral recess stenosis?
Here’s a thread on lateral recess anatomy & a grading system for lateral recess stenosis
2/First anatomy.
Thecal sac is like a highway, carrying the nerve roots down the lumbar spine.
Lateral recess is part of the lateral lumbar canal, which is essentially the exit for spinal nerve roots to get off the thecal sac highway & head out into the rest of the body
3/Exits have 3 main parts.
First is the deceleration lane, where the car slows down as it starts the process of exiting.
Then there is the off ramp itself, and this leads into the service road which takes the car to the roads that it needs to get to its destination
3/At its most basic, you can think of the PPF as a room with 4 doors opening to each of these regions: one posteriorly to the skullbase, one medially to the nasal cavity, one laterally to the infratemporal fossa, and one anteriorly to the orbit