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Vivien Lee MD FAAN Profile picture
Sep 15, 2020 7 tweets 3 min read Read on X
A #stroke #tweetorial. Inferior division MCA infarct often gets mistaken for PCA territory. Sometimes it can be quite difficult to distinguish MCA vs PCA territory infarcts (especially near the borderzone). #neurotwitter #medtwitter #medstudenttwitter
1/ Reminder of topography: MCA (yellow) and PCA (green) territory. Inferior division MCA (near the borderzone of PCA) involves the occipital lobe
3/ This is an example of a patchy MCA territory infarct. Note that the inferior division MCA affects the partieto-occipital lobe (except for the very medial portion of the occipital lobe, which we already stated is PCA). Red line indicates the borderzone between MCA/PCA
4/ Why does it matter? Confusing the territory of the infarct can mislead the clinician to the wrong mechanism/subtype. Also, infarct territory is relevant for purposes of designating a carotid stenosis symptomatic (which requires urgent intervention) vs asymptomatic stenosis.
5/ A patient has a small parieto occipital infarct on MRI DWI (arrow) and a high-grade left carotid stenosis. This infarct (arrow) is actually inferior division MCA and the carotid stenosis is symptomatic (There are also other MCA infarcts visible in this case)
6/ Also keep in mind, the territory maps show you averages, and there is variation in individuals on the territory distributions. The image below denotes maximum, usual, and minimum territory for MCA (and there can be quite a bit of variability in the spread)
2/ This is an example of a full PCA territory infarct on MRI DWI in a patient with a PCA occlusion. PCA infarct affects the very medial occipital lobe. In a very proximal PCA occlusion, thalamus/midbrain can also be affected.

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More from @VivienHLee

May 28, 2021
🧵For those of you using @viz_ai CT brain perfusion automated software for #stroke, here's a tip to avoid the pitfall of under-calling perfusion defect. This educational tip was helpful to our teams.

#MedTwitter #neurotwitter #tweetorial 🧠
1) Example Case. 60yo F with acute right hemiplegia, LKN 12 hours ago, NIHSS 10. Noncontrast CT brain is negative. @viz_ai CTA autodetection goes off to alert for LVO and you can see left M1 occlusion below. Image
2) @viz_ai CTP software reports CBF 0cc/Tmax >6sec =6 cc indicating small penumbra (green). This CTP does not make sense with known LVO and clinical deficits. Something is not right. So what now?

Scroll to 2nd page by clicking arrow (red circle) Image
Read 6 tweets
Oct 3, 2020
1) @realDonaldTrump likely was infected with #COVID19 at the @WhiteHouse superspreader event for Amy Coney Barrett, based upon the timeline of events and what we know about COVID transmission

First, reviewing the evidence on #COVID19 transmission... Image
2) The average incubation of #COVID19 is ~ 5 days (median 5.1, mean 5.5). Fewer than 2.5% of those infected show symptoms within 2.2 days of exposure, and symptom onset will occur within 11.5 days for 97.5% of those infected
acpjournals.org/doi/10.7326/M2… Image
3) Timeline of events:
- Sat 9/26 @WhiteHouse Superspreader event (180 people, no mandatory masking, lack of social distancing precautions)
- Tues 9/26 Debates (Trump party arrives late and skips testing by Cleveland Clinic)
- Thurs 10/1 Trump tweets late evening he has#COVID19
Read 12 tweets

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