2/The first step is to insert the endoscope into the nasal cavity.
The first two structures encountered are the nasal septum and the inferior turbinate.
3/So on every sinus CT you read, the first question is whether there is enough room to insert the scope. Will it go in smoothly or will it be a tight fit?
4/Prominent nasal septal deviation or enlarged turbinates can make it difficult. It is important to alert the surgeon to these. This may require a septoplasty or turbinate reduction in addition to the FESS, and you want them to be aware ahead of time
5/Next step is advancing the endoscope to the middle turbinate. It is an important landmark in FESS. Previously, FESS would often fail b/c of adhesions occurring after surgery between the mid turbinate & lateral nasal cavity wall—causing a new obstruction
6/So now, to prevent this, the middle turbinate is medialized.
A suture used to tie the turbinate to the nasal septum—keeping it medial, like a seat belt holding you in place.
Eventually, scar will make the positioning permanent.
7/Next step is an uncinectomy. This step is used to open up the drainage pathway of the maxillary sinus—like popping the cork off champagne to open it up.
To understand how this works, you have to understand how the maxillary sinus drains
8/Maxillary sinus cavity is the antrum.
Think of the movement of mucus like the movement of travelers.
Antrum is like the airport—where all the people congregate, waiting to move out to their final destination. Mucus needs to leave the antrum
9/The first door to exit the antrum is the ostium. Think of it like the airport gate to enter a plane. It lets you out of the airport—but you aren’t on the plane yet.
10/Just like an airport gate leads you out of the airport into a long hallway—the jetway—the ostium opens to a hallway-like structure called the infundibulum. Just how you must walk down a jetway to get to the plane, you must go through the infundibulum before you can truly leave
11/The end of the infundibulum is the hiatus semilunaris—just like how the jetway ends in the door of the plane.
This is the exit that finally allows you to leave the maxillary sinus drainage pathway—just how entering the airplane finally allows you to take off.
12/The hiatus semilunaris opens into the middle meatus—a space in the nasal cavity that is a common meeting point for many drainage pathways. Think of it like the jet plane. People from many different places come together on one plane & now can head off to their final destination
13/Here is a summary of the maxillary sinus drainage—from the airport (antrum), you exit through the gate (ostium), before traversing down a jetway (infundibulum) to go through the jet door (hiatus semilunaris), that lets you join your fellow travelers on the jet (middle meatus)
14/Uncinate process is the wall helping to create this drainage pathway. It must be taken off to expose, or open up, the door of the natural maxillary ostium
15/Taking down the uncinate process exposes the natural maxillary ostium
You must be careful to alert the surgeon to findings that would increase the risk of violating the orbit when they take down the uncinate, such as an atelectactic uncinate process against the orbit
16/The ostium is the natural endpoint for the mucociliary flow in the maxillary sinus.
Mucus will be propelled towards the ostium—so if the ostium is opened up, more mucus flow can get through.
How much to open it up?
17/Minimum is a uncinectomy (just taking down the uncinate).
This can further be enlarged front to back in a type 1 sinusotomy—or enlarged both front to back & up and down for a type 2 sinosotomy.
Largest is a type 3 sinosotomy—usually for polyposis
18/Next is an ethmoidectomy.
Anterior ethmoid air cells have to be cleared all the way to the skull base.
So mention any findings that could increase risk of perforation of the skull base, such as a deep cribiform plate.
19/If the disease is only involving the anterior drainage, these four steps make up the steps of FESS.
Posterior disease requires more extensive surgery, but that’s for another tweetorial, I must conFESS!
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@TheAJNR 2/In the lumbar spine, it is all about the degree of canal narrowing & room for nerve roots.
In the cervical spine, we have another factor to think about—the cord.
Cord integrity is key. No matter the degree of stenosis, if the cord isn’t happy, the patient won’t be either
@TheAJNR 3/Cord flattening, even w/o canal stenosis, can cause myelopathy.
No one is quite sure why.
Some say it’s b/c mass effect on static imaging may be much worse dynamically, some say repetitive microtrauma, & some say micro-ischemia from compression of perforators
1/Do radiologists sound like they are speaking a different language when they talk about MRI?
T1 shortening what? T2 prolongation who?
Here’s a translation w/an introductory thread to MRI.
2/Let’s start w/T1—it is #1 after all! T1 is for anatomy
Since it’s anatomic, brain structures will reflect the same color as real life
So gray matter is gray on T1 & white matter is white on T1
So if you see an image where gray is gray & white is white—you know it’s a T1
3/T1 is also for contrast
Contrast material helps us to see masses
Contrast can’t get into normal brain & spine bc of the blood brain barrier—but masses don’t have a blood brain barrier, so when you give contrast, masses will take it up & light up, making them easier to see.
1/Asking “How old are you?” can be dicey—both in real life & on MRI! Do you know how to tell the age of blood on MRI?
Here’s a thread on how to date blood on MRI so that the next time you see a hemorrhage, your guess on when it happened will always be in the right vein!
2/If you ask someone how to date blood on MRI, they’ll spit out a crazy mnemonic about babies that tells you what signal blood should be on T1 & T2 imaging by age.
But mnemonics are crutch—they help you memorize, but not understand. If you understand, you don’t need to memorize
3/If you look at the mnemonic, you will notice one thing—the T1 signal is all you need to tell if blood is acute, subacute or chronic.
T2 signal will tell if it is early or late in each of those time periods—but that type of detail isn’t needed in real life
Here's a little help on how to do it yourself w/a thread on how to read a head CT!
2/In bread & butter neuroimaging—CT is the bread—maybe a little bland, not super exciting—but necessary & you can get a lot of nutrition out of it
MRI is like the butter—everyone loves it, it makes everything better, & it packs a lot of calories. Today, we start w/the bread!
3/The most important thing to look for on a head CT is blood.
Blood is Bright on a head CT—both start w/B.
Blood is bright bc for all it’s Nobel prizes, all CT is is a density measurement—and blood is denser (thicker) than water & denser things are brighter on CT
MMA fights get a lot of attention, but MMA (middle meningeal art) & dural blood supply doesn’t get the attention it deserves.
A thread on dural vascular anatomy!
2/Everyone knows about the blood supply to the brain.
Circle of Willis anatomy is king and loved by everyone, while the vascular anatomy of the blood supply to the dura is the poor, wicked step child of vascular anatomy that is often forgotten
3/But dural vascular anatomy & supply are important, especially now that MMA embolizations are commonly for chronic recurrent subdurals.
It also important for understanding dural arteriovenous fistulas as well.