uncal herniation findings

[cassieandcheeta]

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Hi everyone,

Could anyone please explain why the four things they said in FA happen in uncal herniation: ipsilateral dilated pupils.ptosis, contralaterla, homonymous hemanopia, ipsilateral paresis and duret hemorrhage?

thanks so much!

 

[Instatewaiter]

the thing you are going to find universally is ptosis and pupils comes from compression of CN III (note that parasymp runs w/ III so that gives you the dilation, ptosis is from III b/c it does levator palpebri)

The eye is deviated down and out (also III)

Durrets hemorrhages comes from compression of the midbrain

The homonymous hemianopsia occurs b/c the herniation compresses the PCA (post cerebral artery) causing loss of blood to the occipital lobe--> homonymous hemianopsia

The ipsi paresis is actually paradoxical. You would expect a contralateral paresis. But because the herniation compresses the opposite side you see ipsilateral.

 

[Its_MurDAH]

the thing you are going to find universally is ptosis and pupils comes from compression of CN III (note that parasymp runs w/ III so that gives you the dilation, ptosis is from III b/c it does levator palpebri)

The eye is deviated down and out (also III)

Durrets hemorrhages comes from compression of the midbrain

The homonymous hemianopsia occurs b/c the herniation compresses the PCA (post cerebral artery) causing loss of blood to the occipital lobe--> homonymous hemianopsia

The ipsi paresis is actually paradoxical. You would expect a contralateral paresis. But because the herniation compresses the opposite side you see ipsilateral.

yea it's called a "false localization" sign for the exact reason stated above. It is due to damage to the CONTRALATERAL crus cerebri. I believe the term Kernohan's notch is also used to describe this phenomenon but I could be mistaken. And the duret hemorrhages are due to damage to the paramedian arteries. The eye findings are, as explained by the previous poster, due to CN III palsy or 'stretching'.