Lea Alhilali, MD Profile picture
May 27, 2022 6 tweets 4 min read Read on X
1/Kids now out of school? Headache already?? Usually neuroimaging doesn’t add much in headaches, but in occipital neuralgia MR neurography can add a lot.

A🧵about the use of MR neurography in occipital neuralgia
#MedTwitter #MedEd #neurorad #FOAMed #Headache #occipitalneuralgia Image
2/ There are actually 3 occipital nerves:greater, lesser and least. They arise from the upper cervical nerves and innervate various areas of the dorsal scalp. The greater occipital nerve is the only one large enough to image and it arises from C2 Image
3/The greater occipital nerve is the largest cutaneous nerve in the body and can be traced from its origin at the dorsal ramus of C2 along the scalp in MR neurography Image
4/Many pathologies can affect the greater occipital nerve, but most commonly, it is compression between muscles, resulting in occipital neuralgia. This is the basis behind Botox treatment for occipital neuralgia. Decompressive surgery can also be used to provide relief Image
5/Where is it compressed? Usually between the multifidus and semispinalis capitis. We can use MR neurography to rule out other pathologies of the nerve and confirm compressive injury Image
6/MR neurography can confirm unilateral dz preop or post op neuromas w/persistent pain. This is a pt w/unilateral right dz w/a brighter larger right nerve, indicating Sunderland 1 injury from compression

Not all headaches have to be a diagnostic headache with MR neurography 😉 Image

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More from @teachplaygrub

Jul 15
1/Ready for a throw down?

MMA fights get a lot of attention, but MMA (middle meningeal art) doesn’t get the attention it deserves!

This month’s @theAJNR SCANtastic tells you all you need to know!

ajnr.org/content/47/6/1…Image
@TheAJNR 2/Everyone knows brain blood.

Circle of Willis anatomy is king, while the vascular anatomy of the blood supply to the dura is the poor, wicked step child of vascular anatomy that is often forgotten Image
@TheAJNR 3/But dural vascular anatomy & supply are important, especially now that MMA embolizations are commonly for chronic recurrent subdurals.

It is also important for dural arteriovenous fistulas. Image
Read 18 tweets
Jul 10
1/Nothing strikes fear into the heart of a radiologist like the question,“Is it safe to do an MRI on this pt w/an implanted device?”

Do questions about pacemakers & MRIs send your heart racing?

Never fear again! Here’s a thread on how to navigate implanted devices & MRI! Image
2/MRI & CT are like nuclear & coal power, respectively. Everyone knows CT is worse for you & usually MRI is very safe & better for your body

But like nuclear power, when things go bad in MRI, they can go very wrong. Flying chairs into the magnet wrong. So, people are afraid. Image
3/The trouble is from the magnetic attractive forces. There are 3 ways these attractions can wreak havoc. First is translation.

Magnet literally pulls an object, like a chair, towards itself. This is the strongest attraction—like two lovers who literally can’t stay apart. Image
Read 19 tweets
Jun 29
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 Image
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 Image
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 Image
Read 21 tweets
Jun 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
Jun 1
1/Having trouble remembering how to differentiate dementias on imaging?

Is looking at dementia PET scans one of your PET peeves?

Here’s a thread to show you how to remember the imaging findings in dementia & never forget! Image
2/The most common functional imaging used in dementia is FDG PET. And the most common dementia is Alzheimer’s disease (AD).

On PET, AD demonstrates a typical Nike swoosh pattern—with decreased metabolism in the parietal & temporal regions Image
3/The swoosh rapidly tapers anteriorly—& so does hypometabolism in AD in the temporal lobe. It usually spares the anterior temporal poles.

So in AD look for a rapidly tapering Nike swoosh, w/hypometabolism in the parietal/temporal regions—sparing the anterior temporal pole Image
Read 16 tweets
May 1
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. Image
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 Image
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. Image
Read 20 tweets

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