NBME 7 - Doubt ?

[MegaKleos]

To the mods/admins: In line with the SDN policy on NBME questions.. this question is not violating copyright of NBME as i have not posted any direct info.. its indirectly asking a question that was on NBME 7.. Hence please do not remove this post.. it falls under "fair use" of the copyright act.

A man is brought with features of: Severe Headache + Weakness on Lt side - 3 hrs after falling from a ladder and hit his head on the road below.
There was a brief period of unconsciousness but currently the patient is awake.
BP: 160/110

Rt pupil : Dilated
Lt Pupil : Normal

Lt Upper and lower extremity weakness

What would CT show:

1. Brain Stem Hemorrhage
2. Cerebeller Tonsil herniation
3. Cingullate gyrus herniation
4. Uncus herniation
5. SAH


The key says its an UNCUS herniation.. But i disagree..


In uncus herniation following features are seen:

- Ipsilateral 3rd CN palsy - Ipsilateral eye down & out + mydriasis + ptosis
- Ipsilateral PCA involvement - Contralateral Homonymous Hemianopia with Macular Sparing
- Duret Hemorrhage because of paramedian artery rupture in pons
- Contralateral Kernohan's notch impingement with contralateral crus cerebri involvement leading to ipsilateral spastic paralysis of the upper and lower limbs. --> This is the false localizing sign


So in uncal herniation causes : ipsilateral pupillary dilation + ipsilateral UMN paralysis..

But the question says contralateral paralysis and hence i believe it should be Brainstem hemorrhage..

Please pitch in.. Thanks..

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[Scrubs101]

I don’t believe contralateral kernohans notch always has to happen in uncal herniation. Think thats only after severe growth of the hematoma.

Also this is an external compression on cn3 so no motor deficits are necessary if its not severe.

I think theyre going for epidural hematoma cause by blunt force trauma with the description of the injury. Brain stem hemorrhage would be someone w hypertension, afib diabetes, etc though they can be caused by trauma as well. The stem seems much more pathopneumonic for epidural hematoma, however the high BP of this patient makes it confusing. Also for a brainstem hemorrhage to cause this it would be right medial midbrain, and from what ive read brainstem hemorrhages are most common in the pons.

With neuro i feel like theres 1000 possible presentations for even the smallest lesion (medial midbrain can benedikt syndrome and alternating oculomotor hemiplegia, corticobulbar signs etc)

I feel like with these questions were its really possible to be both you just have to go with what the test maker wants you to choose and hope theyre not tricking you and based on that id go with epidural hematoma -> uncal herniation.

Sorry if this isnt much help just kinda listed how i thought it through/some quick “most likely” facts i looked up just now


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[MegaKleos]

I dont agree with a few things you wrote..
Following is factually inaccurate:
Wallenberg aka Lat Medullary syndrome is the MC brainstem stroke NOT pons..

Also, if it is uncal herniation what would account for the ipsilateral paralysis of the body ?

 

[Scrubs101]

Brainstem hemorrhage

"Brainstem hemorrhage, in order of frequency, is seen in the pons, midbrain, and medulla."

I read it as ipsilateral CN3 parasymp dysfunction, contralateral paralysis and so I'm assuming the hematoma is on right side, unless i missed something.

 

[roupeeg92]

An uncal herniation is usually associated with an ipsilateral mass effect with contralateral motor signs. The contralateral Kernohan's notch impingement (with ipsilateral motor signs) is listed as something relatively unique to uncal herniation but it only happens in around 20-25% of cases (think sensitive not specific).

Furthermore, the history and clinical presentation are inconsistent with a brainstem hemorrhage.