USMLE Neurology 20 Neuro Pathology: Herniations

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/ lymed Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day.
Follow along with First Aid, or with my notes which can be found here:
www.dropbox.com/sh/8uams03zbp...
We are all done with neuro anatomy! Can you believe it? Well now that you understand the anatomy of the nervous system, we can discuss neuropathology. We start our first video on neuro pathology on a discussion of herniations.
The skull is a confined space and too much pressure can push structures and displace them. This is called herniation. There are there main structures that the brain can go through, including the falx cerebri, tentorium cerebelli, and the foramen magnum. This results in herniations including:
Cingulate (or subfalcine) herniation : herniation under the falx cerebri, which can compress the anterior cerebral artery.
Downward transtentorial (central) and uncal herniations: these deal with herniation through the tentorium cerebrelli. Downward herniations push the brainstem downward, which can cause Duret hemorrhages. Uncal herniations cause a myriad of symptoms, including CN III palsy (down and out), affect the ipsilateral PCA.
The last one is cerebellar tonsillar herniation, in which the cerebellar tonsils go through the foramen magnum. This again can compress the brain stem and cause death.

[@LYMedVids]

Thanks for watching! If you found these videos helpful, please consider supporting me at www.patreon.com/LYMED
Much love, -Mike

[@Nooberschannel]

Great video but I believe this is what happens during an uncal herniation:
Herniation of the uncus compresses the ipsilateral CN III (which we know is located both near the PCA and is in the brainstem) which gives you a dilated pupil, CNIII palsy and contralateral hemianopia from PCA involvment. The uncus compresses the contalateral crus cerebri (which transmits corticiobulbar and corticospinal tracts which have not decussated yet as this occurs lower in the medulla ) against the kernohan notch which produces paralysis on the side IPSILATERAL to the side of herniation hence false localization as usually brain lesions give contralateral symptoms.

[@zeuskraken7804]

U r a person of up to point .no blah blah only high yield .keep on going

[@abdullahnoor3465]

Really enjoyed it Michael!!:) Cant believe I know you look like in person :)

[@sanjalebi]

Thanks, the way you broke it down made it easy to understand!

[@LYMedVids]

Thank you! I'm glad you enjoyed it.

[@lourdesdunlap5642]

Thanks! Easy to understand brain herniation.

[@samiamahmud5306]

Great video!

[@ED-ez8yd]

awesome video :)

[@missiongamer4494]

Thanks great explanation

[@kiprasmisiunas5052]

Which cerebellar peduncle (superior, inferior or middle) does it press on uncal herniaton?

[@LYMedVids]

Commonly the superior, but it can affect multiple peduncles. I don't believe the distinction is not made on the USMLE.

[@shivani4546]

Cerebral peduncle is compressed not cerebellar. Cerebral peduncle is crus cerebri part part of midbrain.

[@kiprasmisiunas5052]

BTW it is a very nice video

[@saintsam7397]

Why is there contralateral hemiperesis?

[@hariskhan-xj4wk]

there will be ipsilateral paresis...he is wrong

[@shivani4546]

The opposite CEREBRAL peduncle which has the corticospinal tract is compressed in uncal herniation..not CEREBELLAR peduncle

[@jaygarlo9712]

Chill

[@Nooberschannel]

drove me mad going back through my notes