CN IV Lesion - Pupil Position?

[DrTacoElf]

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Can anyone tell me what direction the eye will be if there is damage to CN IV.

I know CN III would be down and out
I know CN VI would be medial

But I can't seem to find a definitive answer on CN IV. Just that the patient will have problems descending stairs and will tilt their head towards the lesion if before decussation and away from lesion if after decussation.

Goljan in his audio says eye will be down and in but that makes no sense considering they have trouble descending stairs (according to yale cranial nerves site).

Based on the chart of page 419 in FA 2010 and vector resolution it seems the eye should be up and out but that contradicts Goljan so thats my confusion....

 

[username456789]

Can anyone tell me what direction the eye will be if there is damage to CN IV.

I know CN III would be down and out
I know CN VI would be medial

But I can't seem to find a definitive answer on CN IV. Just that the patient will have problems descending stairs and will tilt their head towards the lesion if before decussation and away from lesion if after decussation.

Goljan in his audio says eye will be down and in but that makes no sense considering they have trouble descending stairs (according to yale cranial nerves site).

Based on the chart of page 419 in FA 2010 and vector resolution it seems the eye should be up and out but that contradicts Goljan so thats my confusion....

FA errata state up and out.

Additionally, http://cim.ucdavis.edu/eyes/version1/eyesim.htm

 

[DrTacoElf]

FA errata state up and out.

Additionally, http://cim.ucdavis.edu/eyes/version1/eyesim.htm

Cool thanks. So that means the direction of lens dislocation in Marfans and CN IV lesion are the same direction 😀

 

[InTheMaking]

CN IV normally intropes the eye, so the eye would be extroped. The patient would tilt his/her head away from the lesioned side. Therefore a R IV lesion would have a patient tilting their head to the left.

 

[DrTacoElf]

CN IV normally extropes the eye, so the eye would be introped. The patient would tilt his/her head away from the lesioned side. Therefore a R IV lesion would have a patient tilting their head to the left.

http://www.med.yale.edu/caim/cnerves/cn4/cn4_6.html

seems to contradict what you said

 

[IMGUSMLEStep1]

CN IV INTORTS the eye. the Superior oblique passes backwards from the trochlea (which is medial) to a lateral insertion in the posterior part of the eye. Try to imagine how a pull in this direction would lead to intorsion.

So in CN IV palsy, the eye would be extorted, that's why the patient needs to tilt his head to the opposite side.

Here's a great video that explains what I said in a more visual way.
http://www.youtube.com/watch?v=AWJg3Juuhvw

 

[InTheMaking]

Oops... yea I wrote them backwards... my bad.

 

[username456789]

Oops... yea I wrote them backwards... my bad.

Also, not to get pedantic on semantics, but I've never heard of "intrope" and "extrope" before.

 

[Sol Rosenberg]

I always thought that patients tilt their head towards the side with the lesion. With the 4th nerve palsy, the affected eye moves superiomedially (here is some ascii art, X = eye position, I'm showing a R 4th nerve palsy.)

R L
--X ---
--- -X-
--- ---

Wouldn't the patient tilt their head to the right to lower the right eye and raise the left eye to bring them back to their original positions? I watched the youtube video above, but he didn't really explain this well. Could someone help me out here?

 

[username456789]

I always thought that patients tilt their head towards the side with the lesion. With the 4th nerve palsy, the affected eye moves superiomedially (here is some ascii art, X = eye position, I'm showing a R 4th nerve palsy.)

R L
--X ---
--- -X-
--- ---

Wouldn't the patient tilt their head to the right to lower the right eye and raise the left eye to bring them back to their original positions? I watched the youtube video above, but he didn't really explain this well. Could someone help me out here?

The problem is with extorting. The right eye is essentially extorted and therefore you need to "intort" your head (lean your head to the left to intort the right eye). In the process, the healthy left eye will intort normally to maintain clear vision.

HY Neuro has a decent diagram. As I understand, the problem is with rotation, not elevation. But please correct me if I'm wrong.

 

[username456789]

Also, watch out for idiotic sources that use "lean the chin to X side", since it's very confusing and no normal person talks that way. Much simpler to talk in terms of leaning your head in relation to your neck (in which case your chin leans in the opposite direction).