Lea Alhilali, MD Profile picture
Jan 10, 2023 19 tweets 9 min read Read on X
1/Talk about twisting your back! Do spine vascular lesions make your brain feel tangled like the dilated vessels you see?

Here’s a #tweetorial on #spine vascular #anatomy & dural arteriovenous fistulas (dAVF)

#medtwitter #meded #FOAMed #neurotwitter #neurosurgery #neurorad Image
2/To understand spinal dural AVFs, you need to understand basic spinal vascular anatomy.

The spine is LONG—to get blood from the top of the cord to the bottom is like going through the length of a marathon course Image
3/So we will need to tackle it like you tackle running a marathon.

When you run a marathon, you replenish yourself at aid/water stations along the way so you can make it all the way through.

Same w/spinal arterial vasculature—it needs to be replenished on the way down. Image
4/The aid stations that replenish the spinal arteries on the way down are the radiculomedullary arteries. They arise from the radicular arteries (radiculo-) and go to the cord (-medullary). They give a boost to the anterior & posterior spinal arteries on their way down the spine Image
5/Initially, in the fetus, the spinal arteries are replenished at every level.

But slowly, some radiculomedullary arteries regress, leaving only the radicular arteries from which they came.

Other hypertrophy to compensate, so there’s only replenishment at certain levels Image
6/It is kind of like training for a marathon.

Early, you need to stop at every water station to replenish.

But as you grow & get stronger, you learn how to get more out of every aid station & you only have to use a few to replenish Image
7/Largest of the radiculomedullary arteries that hypertrophied & remains is called the Artery of Adamkiewcz. It has a classic “hairpin” turn.

Other radiculomedullary arteries also can have such a turn, but Adamkiewcz will be the largest. Remember Adam was important & strong! Image
8/Radicular arteries supplying the radiculomedullary vessels live in the dura of the nerve root sleeve (nerves give you RADICULAR pain--so by the nerves is RADICULAR artery)

Radicular veins are here too, draining this region into the perimedullary venous plexus along the cord Image
9/In addition to giving off branches that supply or drain to the cord, radicular arteries and veins also supply/drain the adjacent pedicle and nerve root in this region Image
10/The fistula forms in the nerve root sleeve. No one knows exactly why. Some think the Glomerulus of Manelfe, which regulates venous pressures here, causes fistulas.

Regardless, increased pressure in the arterialized radicular vein backs up into the perimedullary plexus Image
11/So the dilated vessels you see on MR & angiograms IN THE CANAL, are NOT the fistula

Rather, these are the dilated perimedullary plexus--resulting from high arterial flow in the radicular vein backing up into the perimedullary plexus Image
12/The fistula itself is not in the canal, but in the nerve root sleeve

But it is connected to all of the dilated perimedullary venous plexus vessels in the canal we see on imaging and associate with spinal dural AVFs Image
13/On an MRA for spinal dAVF, you won’t usually see the fistula—it’s too small. But you'll see the dilated, arterialized radicular vein draining into the dilated perimedullary plexus.

So it’s your job to find the level of the dilated radicular vein—b/c that’s the fistula level! Image
14/The fistula causes damage b/c the perimedullary plexus isn’t made to carry arterial volume. It’s like drinking from a slow faucet & then suddenly having it turned on all the way—you’ll choke!

Fistulas cause veins to be overloaded, get wall thickening, & eventually shut down Image
15/Arterialized venous pressure & veins shutting down from overload causes venous congestion in the cord.

Even though the radicular vein itself doesn’t drain the cord, it drains to the perimedullary plexus, which drains the cord

So perimedullary hypertension affects the cord Image
16/It’s like an accident on a freeway exit ramp. Even if you aren’t on the exit ramp, the exit ramp backup eventually backs onto the highway—so even cars not using that exit are affected

Even though the cord doesn’t drain through the radicular vein, the venous backup affects it Image
17/ B/c there is a pressure gradient in the upright position & the cspine has better venous drainage, congestion is most pronounced caudally, even if the fistula is higher.

So you cannot use the location of veins or cord edema to localize the fistula! Image
18/Venous cord congestion causes the classic Foix-Alajounine syndrome. Venous hypertension from the fistula causes veins to overload & shut down. This causes more HTN & more shutdown.

This feed forward loop causes slowly greater venous cord edema & slowly progressive myelopathy Image
19/So now you understand the anatomy and pathology behind spinal dural arteriovenous fistulas!

Hopefully, this tweetorial didn’t overload you & cause some information hypertension! Image

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Lea Alhilali, MD

Lea Alhilali, MD Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @teachplaygrub

Sep 15
1/Time is brain!

So you don’t have time to struggle w/that stroke alert head CT.

Here’s a thread to help you with the CT findings in acute stroke! Image
2/CT in acute stroke has 2 main purposes

(1) exclude hemorrhage (a contraindication to thrombolysis)

(2) exclude other pathologies mimicking acute stroke. But you can also see other findings to help diagnosis a stroke. Image
3/Infarct appearance depends on timing.

In first 12 hrs, the most common imaging finding is…a normal head CT

However, you may see a hyperdense artery or basal ganglia obscuration. Later, you see loss of gray white differentiation & sulcal effacement Image
Read 13 tweets
Sep 12
1/Do you feel there’s a back-log of findings in a spine MRI report?

Everyone talks about discs & facets, but not everyone talks about the endplates

Do you?

Do you need to talk about degenerative changes (Modic changes) of the endplates?

Here’s thread w/all you need to know! Image
2/Over 30 years ago, Modic et al. found there were 3 types of degenerative endplate changes:

(1) T2 bright changes (indicating edema, Modic 1)
(2) T1 bright changes (indicating fat, Modic 2)
(3) T1 & T2 dark changes (indicating sclerosis, Modic 3)

But what do they mean? Image
3/Let’s start w/Modic 1.

These are bright on T2, indicating edema

On pathology, it’s what you’d expect w/edema: inflammation, vascular granulation tissue, & high cellular turnover

Vascular granulation tissue means these can enhance on post contrast images—mimicking discitis! Image
Read 18 tweets
Sep 10
1/Are you FISHING for a way to better evaluate subarachnoid hemorrhage?

Are you hungry for a way to classify these patients?

Donut you worry!

Here’s a short thread to help you remember the modified Fisher scale for classifying subarachnoid hemorrhage. Image
2/Just think of the brain as a donut. Like a donut, it’s a bunch of stuff around a hole in the middle.

Ventricles are the hole in the middle of the brain just like there’s a hole in the middle of the dough in a donut.

Just don’t quote me to your neuroanatomy professor…. Image
3/Subarachnoid hemorrhage (SAH) added to the brain makes it less healthy, the same way adding toppings to a donut makes it less healthy.

Increasing severity of SAH is like increasingly unhealthy donut toppings. Fisher scale quantifies the vasospasm risk for increasing SAH Image
Read 8 tweets
Sep 8
1/Talk about twisting your back!

Do spine vascular lesions make your brain feel as tangled as the dilated vessels you see?

Want some more information on malformations?

Here’s a thread on spine vascular anatomy to give you durable knowledge on dural arteriovenous fistulas (dAVF)Image
2/To understand spinal dural AVFs, you need to understand basic spinal vascular anatomy.

The spine is LONG—to get blood from the top to the bottom is like going through the length of a marathon course Image
3/So we will need to tackle it like you tackle running a marathon.

When you run a marathon, you replenish yourself at aid/water stations along the way so you can make it all the way through.

Same w/spinal arterial vasculature—it needs to be replenished on the way down. Image
Read 19 tweets
Sep 3
1/Does the work up for dizziness make your head spin?

Wondering what to look for on an MR for dizziness

This month’s @theAJNR SCANtastic will tell you all you need about imaging Meniere’s disease!

ajnr.org/content/46/8/1…Image
@TheAJNR 2/The etiology for dizziness can have very diverse causes—each with very different treatments.

So it is important to try to differentiate

Meniere’s is a common cause & we can help diagnose it w/imaging! Image
@TheAJNR 3/To understand Meniere’s disease, you must know labyrinth anatomy

It has layers, like Russian nesting dolls. Outer doll is the bony labyrinth, holding perilymph & a second doll—membranous labyrinth.

Inside the membranous labyrinth is endolymph Image
Read 13 tweets
Aug 1
1/They say form follows function!

Brain MRI anatomy is best understood in terms of both form & function.

Here’s a short thread to help you to remember important functional brain anatomy--so you truly can clinically correlate! Image
2/Let’s start at the top. At the vertex is the superior frontal gyrus. This is easy to remember, bc it’s at the top—and being at the top is superior. It’s like the superior king at the top of the vertex. Image
3/It is also easy to recognize on imaging. It looks like a big thumb pointing straight up out of the brain. I always look for that thumbs up when I am looking for the superior frontal gyrus (SFG) Image
Read 12 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

:(