2/A key concept in these fxs is dental occlusion. The jaw is meant to chew. To crush food, teeth need to come as close together as possible—occlusion. Each tooth needs to meet up with its counterpart that fits with it, so no room is left for food—and food will be crushed.
3/Occlusion can be lost w/a fx. The importance of dental occlusion makes mandibular fxs different from other fxs. Usually, we want to fix a bone so that it lines up again. But for the mandible, we want to fix it so the TEETH line up again—so chewing will work.
4/Another important concept is multiplicity. It used to be taught that the mandible was a ring w/the skullbase—& you can’t break a ring in one place, so every mandible fx had to have a 2nd one. But this is only true ~50% of time—but it is still worth it to look for the 2nd fx.
5/Because of the shape of the mandible and the typical forces applied to it, mandibular fractures usually occur at the same few locations. But the names of these fxs are not always intuitive—at least not without a tweetorial to help explain them! 😉
6/Well, perhaps I lied a little. The most common fx does have an intuitive name. An angle fx starts at…wait for it…the angle and extends into socket of the 3rd molar. If you can’t remember an angle fx starts at the mandibular angle, then not even this tweetorial can help you!
7/A subcondylar fracture starts from the notch between the condyle and coronoid process, called the sigmoid notch and extends into the posterior ramus. Don’t call this a ramus fx bc a ramus fx goes straight horizontally through the ramus!
8/Here are examples of subcondylar fxs. A key finding in subcondylar fxs is that it separates the condyle from the rest of the mandible. It can be difficult to see the fx running through the sigmoid notch & ramus on 2D images—3D images can be helpful to see the fx anatomy.
9/I remember subcondylar fxs bc they separate the condyle from the rest of the mandible. If you isolate someone, you make them feel SUBpar—so SUBcondylar fxs make the condyle feel subpar bc they separate it from the rest of the mandible!
10/Condylar head/neck fxs are easy to remember—they are through, well, the condylar head or neck. These are fx/dislocations. Pterygoid muscles attach to the head & pull medially. So when the head is no longer attached to the mandible, pterygoids are unopposed & pull it medially.
11/So if you ever see a condylar head displaced medially, you know it is a condylar head or neck fracture bc this is where the pterygoids are unopposed and pull medially!
12/Body fxs are through the body of the mandible and are named for the tooth socket that they involve. So you would say “A mandibular body fx through the FILL IN THE BLANK TOOTH socket.”
13/Body fxs through the canine are given the special name “parasymphaseal” or “mental” fx bc they are near the mental foramen where the inferior alveolar nerve exits. Menton means “chin” in French, so if they are a body fx anteriorly near the chin, they are “mental” fxs
14/So now you know your mandibular fractures & you have a plan even when the patient gets punched!
• • •
Missing some Tweet in this thread? You can try to
force a refresh
1/ I always say, "Anyone can see the bright spot on diffusion images—what sets you apart is if you can tell them why it’s there!”
If you don't why a stroke happened, you can't prevent the next one!
Can YOU tell a stroke’s etiology from an MRI?
Here’s a thread to show you how!
2/First a review of the vascular territories.
I think the vascular territories look a butterfly—w/the ACA as the head/body, PCA as the butt/tail, and MCA territories spreading out like a butterfly wings.
3/Of course, it’s more complicated than that.
Medially, there are also small vessel territories—the lenticulostriates & anterior choroidal.
I think they look like little legs, coming out from between the ACA body & PCA tail.
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!
After reading this, when you see a hemorrhage, your guess on its age 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
@TheAJNR 2/Since the prehistoric days of medicine (1979!), we knew that some brain tumor patients treated w/radiation (XRT) initially declined, but then get better.
Today, we see this on imaging, where it looks worse early, but then gets better.
Now we call this pseudoprogression.
@TheAJNR 3/Why does this happen?
XRT induces a lot of inflammatory changes—from initiating the complement cascade to opening the blood brain barrier (BBB)
It’s these inflammatory changes that make the imaging look worse.