Hi #MedTwitter #MedStudentTwitter #neurotwitter #MedEd #FOAMed! It's been too long since my last #EndNeurophobia #tweetorial so here's an introduction to brain imaging–thanks @sarrovasta for the request!🧠❤️
cc:@CPSolvers @rabihmgeha @DxRxEdu @AvrahamCooperMD @caseyalbin
Let's start w/CT. I'll focus on brain (and not bone or soft tissue). First:

* Identify normal structures and any abnormalities in:
- Size
- Shape
- Symmetry
(note *symmetric* abnormalities such as ventriculomegaly or diffuse cerebral edema may not be obvious w/o experience)


* Identify abnormalities
- Hypodensity
- Hyperdensity


• Hypodensity:
- Ischemia
- Inflammation
- Infection
- Neoplasm

• Hyperdensity:
- Blood
- Calcification
- Hyperdense tumors (e.g. lymphoma)
- Thrombus in vessel
- Contrast enhancement

Hypodensities= BROAD DDx. Distinguishing infl v infxn v neoplasm requires clinical context & more imaging.

Distinguishing stroke v the rest: if hypodensity respects gray-white junction= likely NOT stroke. Stroke close to cortical surface =affects both gray & white matter...
Which one is the stroke?
Clinical context would help but, radiologically...

⬆️The left one = hypodensity NOT respecting gray-white junction= ischemic stroke

The right one = respects G-W junction = tumor v infection v inflammation (in this case was toxo but no way to tell from non-con CT alone (let alone no clinical context)

Hyperdensities: blood v calcification v hypercellular mass v IV contrast. Clinical context usually makes distinction obvious. When in doubt, Hounsfield units can distinguish

Here's an intracerebral hemorrhage (left) and neurocysticercosis (right)

Now on to MRI. Here was also look for size/shape/symmetry of normal structures and abnormalities of these or presence of hypointensity or hyperintensity.

But the significance of hypo v hyper depends on the sequence....

T1: Gray matter dark, white matter brighter
T2: Gray matter bright, white matter dark (like a photographic ‘negative’ of T1)

FLAIR: T2 with CSF signal subtracted (makes it easier to see periventricular white matter lesions).

T2 on L, FLAIR on R. Can you see the lesion adjacent to the frontal horn of the right lateral ventricle on the T2? Nope! That's how FLAIR helps!

Blood has different signal characteristics on T1 v T2 depending on age. See this table.
Mnemonic (I = iso, B= bright, D= dark)

DWI/ADC: looks for decreased diffusion of water molecules through tissue (bright on DWI/dark on ADC):
- cytotoxic edema (acute ischemic stroke, ongoing seizure activity)
- tightly packed cells (abscess, lymphoma)
- in cortical ribbon and basal ganglia in CJD

Here: MCA stroke
GRE/SWI: blood and calcium are dark

Here: multiple microhemorrhages in a patient with cerebral amyloid angiopathy (see and by @a_charidimou )
So where to start?
1. As w/CT, look at size/shape/symmetry of structures (often done on T1)

2. FLAIR: look for hyperintensities=pathology

3. T1 pre vs post: look for whether lesions enhance (= blood brain barrier breakdown: inflammation/tumor/infection/subacute stroke)

4. DWI/ADC: look for hyperintense DWI with corresponding hypointense ADC (and remember not all that restricts is stroke; see above)

5. GRE/SWI: look for hypointensities (blood or calcium)

Still don't know the answer with the history, exam, labs and MRI....? Depending on context....
- Consider more imaging (MR Spectroscopy, PET, MR/CT perfusion)
- Consider CSF analysis
- Consider brain biopsy

Want tons of CT and MRI examples of classic and rare diseases? Look up my book on AccessMedicine through your school's digital library for free access!
Want more #Neurology tweetorials?

What should I cover next?


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More from @AaronLBerkowitz

Feb 22
Paul Farmer changed my life before I ever met him. I'm a cliche: I read Mountains Beyond Mountains as a student, my worldview changed, and I decided I wanted to follow in his footsteps and pursue global health equity when I grew up.

But an atypical version of the cliche...
I was a med school dropout/grad student in music when I read MbM! Here's the story, a portrait of Paul at the bedside, an attempt to capture two of the most meaningful moments in my life, a small homage to Paul from one of the countless lives he touched and shaped.💔 2/
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Feb 13
Yes, @Tracey1milligan! How do I #LoveNeurology let me count the ways! 🧠❤️
A 🧵
Below is from a presentation where we each gave a pitch to students why our specialty was the best. All due respect to admired colleagues in other specialties, roasting/humor was encouraged😀
So when trying to choose a specialty, your advisor may ask you what’s your favorite organ?

You’ve heard the arguments:
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Oct 2, 2021
The pupils can constrict (miosis) and dilate (mydriasis)
Mydriasis = bigger word = bigger pupil.

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Dilation is a SYMPATHETIC function (eyes wide with fear)
Pupils constrict in response to LIGHT and NEAR

Pupils dilate in response to DARKNESS and ADRENERGIC TONE

Drugs can also affect the pupils as can prior trauma/surgery
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Aug 22, 2021
Hi #medtwitter #neurotwitter #medstudenttwitter #meded #FOAMed

It's been too long since my last #EndNeurophobia #tweetorial. As requested by @sukritibanthiya here is a tweetorial on MUSCLE DISEASE (MYOPATHY)

Let me know what you think and what I should cover next!
Classic pattern of weakness in myopathy is PROXIMAL symmetric weakness of the limbs, though there are exceptions.

There should be NO sensory findings (unless there is concurrent neuropathy) and reflexes are often spared until the patient is extremely weak.
Difficulty rising from a chair (hip girdle musculature), washing hair (shoulder girdle musculature)

CK is often elevated but not always

EMG can demonstrate myopathic pattern (though can be normal eg statin myopathy)

Definitive Dx may require muscle biopsy and/or genetic test
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I have been asked where to donate for #earthquake response efforts in #Haiti. I donated to @PIH & @StBonifaceHaiti Both partner with local communities and govt to provide healthcare to those in greatest need. #haitiearthquake #globalhealth 💔 cc: @CPSolvers @DxRxEdu @rabihmgeha
@StBonifaceHaiti is probably the best-resourced hospital in the affected region. I visited in 2012 and what was already an extraordinary facility and group of talented dedicated staff has only grown.

@PIH has collaborated with rural communities and the Ministry of Health in Haiti for over 30 years. They were an integral part of the response to the 2010 earthquake, subsequent cholera outbreak, and rebuilding efforts.
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Apr 19, 2021
Excited to attend health equity symposium #AANAM @AANMember supported by Cheryl Jay Endowment. Dr. Jay made incredible contributions to our neurology training program in Haiti and I'll never forget how she took all the applicants out to lunch when I interviewed @neurores_ucsf Image
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Reminds me of one my favorite quotes from Paul Farmer @PIH "History didn't begin when you arrived..." Image
Read 6 tweets

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