Lea Alhilali, MD Profile picture
Aug 18, 2022 9 tweets 6 min read Read on X
1/Does trying to figure out cochlear anatomy cause your head to spiral? Hungry for some help?
Here’s a #tweetorial to help you untwist cochlear CT anatomy w/food analogies!
#medtwitter #FOAMed #FOAMrad #medstudenttwitter #medstudent #neurorad #radres
@MedTweetorials #HNrad Image
2/On axial temporal bone CT, you cannot see the whole cochlea at once. So let’s start at the bottom. The first thing you come to is the basal turn of the cochlea (makes sense, basal=bottom). On axial images, it looks like a banana. I remember both Basal and Banana start w/B. Image
3/As you move up to the next slice, you start to see the upper turns of the cochlea coming in above the basal turn. They look like a stack of pancakes. Pancakes are the heart of any breakfast, so they are at the heart or middle of the cochlea on imaging. Image
4/On this slice showing pancakes, you can see the round window and the round window niche. I remember that this slice is where you can see the round window bc pancakes are ROUND. Image
5/As you move up, you leave the basal turn behind & see only the upper turns. These no longer look like pancakes bc cochlear scala separate them. Instead they look like a bunch of cherries. I know I’m at the cochlea top when I see cherries bc you always put a cherry on top! Image
6/Here’s an easy way to remember the order of the appearance of the cochlea. Starting at the basal turn, B is for banana & basal. Bananas can make banana pancakes, so the next slice is pancakes. Finally, you put a cherry on top of the pancakes, so top of the cochlea is cherries. Image
7/On the coronal plane, you get a sense of the spiral nature of the cochlea. It looks like the spiral of a snail’s shell. Image
8/Looking closely, you can see eyes of the snail on coronal images.Eyes are right in front of the cochlear snail shell—canal of labyrinthine facial nerve segment going anterior & canal of the tympanic segment coming back. Makes sense that the FACIAL nerve canal would be the EYES Image
9/So now you know the anatomy of the cochlea, so it won’t just look like the layered rolls of Jabba the Hutt to you. May the force of this knowledge be with you! Image

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More from @teachplaygrub

Mar 3
1/Does PTERYGOPALATINE FOSSA anatomy feel as confusing as its spelling?

Does it seem to have as many openings as letters in its name?

Are you pterrified of the pterygopalatine fossa (PPF)?

Let this thread on PPF anatomy help you out. Image
2/The PPF is a crossroads between the skullbase & the extracranial head and neck

There are 4 main regions that meet here:

(1) Skullbase itself posteriorly, (2) nasal cavity medially, (3) infratemporal fossa laterally, and (4) orbit anteriorly. Image
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 Image
Read 18 tweets
Feb 28
1/Feel like a fish out of water when it comes to water on the brain?

Read on for this month’s @Radiographics summary of what you need to know about hydrocephalus!!



@cookyscan1 @RadG_editor #RGphx doi.org/10.1148/rg.240…Image
2/To understand hydrocephalus, think of CSF like the flow of traffic

3 main ways traffic backs up:

(1) Obstruction on the road:
For hydrocephalus, this is an obstruction along CSF in the ventricle Image
3/

(2) Obstruction of an off ramp
For hydrocephalus=obstruction at its off ramp into the venous system

(3) Rush hour
For hydrocephalus=over production Image
Read 8 tweets
Feb 27
1/Do scans for dizziness make your head spin?

Need to know what to look for?

Just hear me out!

This month’s @theAJNR SCANtastic will show what to look for:

ajnr.org/content/46/2/3…Image
2/I always remember the rhyme of the big three for dizz-ee!

First, are vestibular schwannomas

These give an ice cream cone shape in the internal auditory canal! So scoop up that finding! Image
3/Next is labyrinthitis

Labyrinthitis can look like night & day, depending on the timing

Late labyrinthitis is dark—loss of bright fluid signal on FIESTA

Early labyrinthitis is bright—enhances on post-contrast Image
Read 12 tweets
Feb 26
1/Time is brain! But what time is it?

If you don’t know the time of stroke onset, are you able to deduce it from imaging?

Here’s a thread to help you date a stroke on MRI! Image
2/Strokes evolve, or grow old, the same way people evolve or grow old

The appearance of stroke on imaging mirrors the life stages of a person—you just have to change days for a stroke into years for a person

So 15 day old stroke has features of a 15 year old person, etc. Image
3/Initially (less than 4-6 hrs), the only finding is restriction (brightness) on diffusion imaging (DWI)

You can remember this bc in the first few months, a baby does nothing but be swaddled or restricted

So early/newly born stroke is like a baby, only restricted Image
Read 10 tweets
Feb 25
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! Image
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. Image
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. Image
Read 18 tweets
Feb 24
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 Image
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.Image
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! Image
Read 9 tweets

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