1/ “You don’t get points for having your needle in the right place if you don’t get a diagnosis.” When we biopsy the skullbase we work to get a diagnosis.
A sort of #tweetorial but more like a 🧵about our skullbase biopsy system. #FOAMed#medtwitter#neurosurgery#neurotwitter
2/ Unless the lesion is difficult to diagnosis w/FNA (ie, schwannoma), we begin by FNA w/an 18g draw needle & a 22g Quincke needle. We do not aspirate, b/c the skullbase is very vascular, & too much blood will be drawn up, making it difficult to tell if the sample is diagnostic.
3/ However, if we are not getting a diagnosis with FNA, we will move to a core. If it is a deep lesion, we will use the Biopince system, beginning with a 17g, 7 cm introducer. This is an example of IgG4 disease of the trigeminal nerve that failed FNA and required a core
4/ Through the 17g introducer, the 18g Biopince needle is inserted for biopsy. You need about 3.5cm of tissue depth to the lesion to support this system. If there is less tissue, there is not enough purchase to hold the introducer in place and it will sag.
5/ For superficial lesions, we change the introducer to a 16g Angiocath IV needle. It has a internal metal stylet, making it easy to steer. This a deep parotid lesion invading the masticator space requiring a core, but was too superficial to support the normal Biopince system.
6/ The Biopince needle fits perfectly into the 16g Angiocath. The tip of the Angiocath stops the Biopince from advancing further, so you will begin the throw for your core immediately from end of your introducer.
7/ The most important thing is to get the patient a diagnosis. I tell the pathologist "I can do this all day." We biopsy lesions until we are told samples are diagnostic. To prove a negative (ie infection not tumor), we sample at least 10 times to avoid undersampling.
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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