cranial nerve 10 vs 12 damage

[Oh_Gee]

why is it that when one of the CN X is damaged, the uvula deviates toward to the normal side (ex: right CN X damaged> uvula deviates to left side)

and

when one of the CN XII is damaged, the tongue deviates to the damaged side (ex: right CN XII damaged> tongue deviates to the right side)
("licking your own wounds" is what BRS says to remember this presentation)

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[Psai]

because the genioglossus pushes the tongue out and cn12 fibers mostly cross to the other side

 

[Wolfpack2014]

Your genioglossus originates from the middle of your mandible (mental spine) and then fans out to the bottom of the tongue, so when it contracts, it pulls forward and toward the midline. Since it is pulling toward the midline, the right side of the muscle pulls to the left and vice versa. If the right side is damaged, when you stick your tongue out the right side can't pull to the left, so the tongue will deviate to the right.

Same idea as for the lateral pterygoid muscles with regard to deviation. They too pull toward the midline so it deviates toward the affected side.

 

[Oh_Gee]

Your genioglossus originates from the middle of your mandible (mental spine) and then fans out to the bottom of the tongue, so when it contracts, it pulls forward and toward the midline. Since it is pulling toward the midline, the right side of the muscle pulls to the left and vice versa. If the right side is damaged, when you stick your tongue out the right side can't pull to the left, so the tongue will deviate to the right.

Same idea as for the lateral pterygoid muscles with regard to deviation. They too pull toward the midline so it deviates toward the affected side.

http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect14_files/image007.jpg

from this picture, it looks like the right side of the genioglossus will pull the tongue away from the midline (to the right) though....

if this is true, it makes sense because if the right CN XII is messed up, then it can't pull right. the left side will protrude further out. since the right side is messed up, it'll drag the left side to the right. i'm so confused

and also in this practice problem where the patient has right tongue deviation, it says

The tongue deviation
to the right is due to the unopposed activity of the left
tongue muscles since the right hypoglossal nerve
(which innervates the right tongue muscles) is affected.

aaaaaaaaaaah

 

[Womb Raider]

The best is when you get to UMN lesions and everything reverses!

 

[coldcase331]

You could just accept it for what it is and not think about it too much. That's how I made it through anatomy


Sent from my iPhone using SDN mobile app

 

[Wolfpack2014]

http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect14_files/image007.jpg

from this picture, it looks like the right side of the genioglossus will pull the tongue away from the midline (to the right) though....

if this is true, it makes sense because if the right CN XII is messed up, then it can't pull right. the left side will protrude further out. since the right side is messed up, it'll drag the left side to the right. i'm so confused

and also in this practice problem where the patient has right tongue deviation, it says

The tongue deviation
to the right is due to the unopposed activity of the left
tongue muscles since the right hypoglossal nerve
(which innervates the right tongue muscles) is affected.

aaaaaaaaaaah

You can't tell anything about left vs right from that picture because it is a 2D representation. All you can tell is that the genioglossus would pull the tongue forward when contracting. If you have Netter's atlas, look at either page 43 or 47. Look up its origin if you don't believe me, it is the mental spine . Draw vector lines if that helps you. It primarily pulls the tongue forward and depresses it but there is a slight pull towards the midline as, which is the cause for the diversion toward the lesioned side. If the left side pulls away from the midline (to the left) while the right side has no pull (as you are saying), it certainly isn't going to divert to the right.

Edit: Sorry, it's kind of hard to show you exactly what happens without being able to draw out the muscles and vector lines for you.

 

[TooMuchResearch]

Because just get a CT scan (or CTA) then probably MRI, sometimes straight to MRI.

In my defense, I don't remember the answer and it doesn't really affect how I do my job. I definitely shouldn't teach you my way, though.

 

[Oh_Gee]

You can't tell anything about left vs right from that picture because it is a 2D representation. All you can tell is that the genioglossus would pull the tongue forward when contracting. If you have Netter's atlas, look at either page 43 or 47. Look up its origin if you don't believe me, it is the mental spine . Draw vector lines if that helps you. It primarily pulls the tongue forward and depresses it but there is a slight pull towards the midline as, which is the cause for the diversion toward the lesioned side. If the left side pulls away from the midline (to the left) while the right side has no pull (as you are saying), it certainly isn't going to divert to the right.

Edit: Sorry, it's kind of hard to show you exactly what happens without being able to draw out the muscles and vector lines for you.

plate 43 really helped. thanks!

what about the uvula deviation though?

 

[Oh_Gee]

You could just accept it for what it is and not think about it too much. That's how I made it through anatomy


Sent from my iPhone using SDN mobile app

I MUST satisfy my curiosity

 

[Wolfpack2014]

plate 43 really helped. thanks!

what about the uvula deviation though?

Pretty sure levator veli palatini is the muscle. I can't remember all the details on uvula deviation with regard to CN IX vs CN X. There are certain ways to tell the difference between which CN is affected, but if you have a vagus nerve lesion, you'll have levator veli palatini weakness which pulls laterally and upward. There are also a few other palate muscles innervated by the vagus nerve, but I'm pretty sure the deviation is primarily due to the LVPM weakness.