tongue deviation and lesion in corticobulbar tract

[MudPhud20XX]

So the way I learned from my nueroanatomy class was that if the tongue is deviated to the right that means the lesion of the CN12 is also on the right side. But here is what Kaplan says:

"Generally, no other cranial deficits will be seen with corticobulbar lesions because virtually every other cranial nerve nucleus is bilaterally innervated. In some idviduals, the hypoglossal nucleus may receive mainly contralateral corticobulbar innervation. If these corticobulbar fibers are lesioned, the tongue muscles undergo transient weakness without atrophy or fasciculations and may deviate away from the inured corticobulbar fibers. If, for example, the lesion is in corticobulbar fibers on the left, there is transient weaknesss of the right tongue muscles, causing a deviation of the tongue toward the right side upton protrusion."

So did I get this wrong from my neuroanatomy class? What am I missing here?

Many thanks in advance.

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[ulikedaggers]

Seems like an error on Kaplan's part.

Edit: Nevermind. The ipsilateral thing that you learned in neuroanatomy is right, but that's only in cases where CN12 itself is damaged. And in those cases you will see fasciculations and atrophy.

Kaplan is correct about corticobulbar lesions.

 

[sanj238]

So the way I learned from my nueroanatomy class was that if the tongue is deviated to the right that means the lesion of the CN12 is also on the right side. But here is what Kaplan says:

"Generally, no other cranial deficits will be seen with corticobulbar lesions because virtually every other cranial nerve nucleus is bilaterally innervated. In some idviduals, the hypoglossal nucleus may receive mainly contralateral corticobulbar innervation. If these corticobulbar fibers are lesioned, the tongue muscles undergo transient weakness without atrophy or fasciculations and may deviate away from the inured corticobulbar fibers. If, for example, the lesion is in corticobulbar fibers on the left, there is transient weaknesss of the right tongue muscles, causing a deviation of the tongue toward the right side upton protrusion."

So did I get this wrong from my neuroanatomy class? What am I missing here?

Many thanks in advance.

This is a concept of UMN vs LMN- the cranial 12 lesion is a LMN. the corticobulbar is an UMN. So both are correct.

LMN- CN12 is found on the same side as lesion. UMN- synapses onto CN12 but originates from contralateral side. corticobulbar is the UMN to ALL of the Cranial nerves. Generally CB provides bilateral so it is asymptomatic except with SOME tongue nerves in some people and is also contralateral only, to the lower facial portion- so if you see drooping of face but upper part of face normal- then you know it is a contralateral facial nerve damage and not a facial nerve lesion itself (complete ipsilateral loss)

fyi what causes fasciciulations of tongue?

 

[MudPhud20XX]

So the fasciculation of the tongue should be caused by lesion on LMN-CN12 since "fasciculation" is the sign of LMN lesion.
Ipsilateral fasciculation of the tongue should be caused by ipsilateral damage in the LMN of the CN12, correct?
Thanks guys for the explanation.

 

[sarah65]

In short, you are correct.

So the fasciculation of the tongue should be caused by lesion on LMN-CN12 since "fasciculation" is the sign of LMN lesion.
Ipsilateral fasciculation of the tongue should be caused by ipsilateral damage in the LMN of the CN12, correct?
Thanks guys for the explanation.

 

[ChessMaster3000]

So the fasciculation of the tongue should be caused by lesion on LMN-CN12 since "fasciculation" is the sign of LMN lesion.
Ipsilateral fasciculation of the tongue should be caused by ipsilateral damage in the LMN of the CN12, correct?
Thanks guys for the explanation.

yep

 

[Apoplexy__]

Interestingly, on a class exam I had last year, one question gave us a constellation of symptoms that included contralateral tongue deviation, which you had to know was UMN in order to localize the rest of the findings. Definitely a testable fact; I'm surprised I never see the concept of CN UMN's in First Aid.

 

[sanj238]

So the fasciculation of the tongue should be caused by lesion on LMN-CN12 since "fasciculation" is the sign of LMN lesion.
Ipsilateral fasciculation of the tongue should be caused by ipsilateral damage in the LMN of the CN12, correct?
Thanks guys for the explanation.

This is also why in ALS its one of the first signs

 

[MudPhud20XX]

Thanks guys.

I'm sorry to bring this up again, but I got to make sure that I know this stuff for sure.

So let's say we got a question that says a patient's tongue was deviated to the left. So basically this could be either left LMN CN12 lesion or (right) contralateral UMN corticobulbar tract lesion. What kind of clues will be given in the question that would help us differentiate if it's the LMN or UMN lesion?

For facial nerves, as sanj238 mentioned, if half of the face is paralyzed it's the contralateral UMN lesion and if the entire half of the face is paralyzed it's the ipsilateral lesion (Bell's Palsy). I get that, but in case of CN12, what would be the clue to differentiate the UMN and LMN?

 

[Fatalis]

I think they would zone in and give you more sx. Like you said, fasciculations would be a clue.

 

[ulikedaggers]

Thanks guys.

I'm sorry to bring this up again, but I got to make sure that I know this stuff for sure.

So let's say we got a question that says a patient's tongue was deviated to the left. So basically this could be either left LMN CN12 lesion or (right) contralateral UMN corticobulbar tract lesion. What kind of clues will be given in the question that would help us differentiate if it's the LMN or UMN lesion?

For facial nerves, as sanj238 mentioned, if half of the face is paralyzed it's the contralateral UMN lesion and if the entire half of the face is paralyzed it's the ipsilateral lesion (Bell's Palsy). I get that, but in case of CN12, what would be the clue to differentiate the UMN and LMN?

Probably muscle atrophy and/or fasciculations. Both of which point to ipsilateral LMN. Alternatively, there could be a vignette about a patient with ectopic thyroid tissue in the right carotid triangle. And the question could be about what other symptoms you would expect. Answer would be tongue deviated to the right.

 

[Apoplexy__]

Alternatively, there could be a vignette about a patient with ectopic thyroid tissue in the right carotid triangle. And the question could be about what other symptoms you would expect. Answer would be tongue deviated to the right.

...What?

 

[ulikedaggers]

...What?

CN12 passes through the carotid triangle and can be compressed by ectopic thyroid tissue. It was a point of emphasis in our anatomy class.. I guess it's not emphasized anywhere else lol.

 

[Ionian]

All the signs for a corticonuclear lesion (a lesion typically of the genu of the internal capsule): (lets say right genu lesion)
Tongue deviation to the left (with no atrophy)
Weak head rotation to the left (CN 11 is only ipsolaterally innervated)
Muscle paralysis of the left lower face
*Uvula deviation to the RIGHT


Motor Nerves which are predominantly contralaterally innervated (just correlate with above symptoms)
CN 12
CN 7 (Facial nerve): lower face only
CN 9,10 (Nucleus ambigus)

Pretty hard to miss this. Tongue deviation alone? LMN lesion.
In association with other cranial nerves (multiple defects: contralateral UMN lesion), because of the close proximity of exiting nerves in the genu of the internal capsule, and this area is more common to have a lesion.

There are cortical lesions outside the genu which can have an Isolated deviation of the tongue but it is extremely rare and you wont be asked about it. It would have to be in a very limited area of the motor cortex:
http://jnnp.bmj.com/content/78/12/1372

So for step. If its UMN tongue deviation, its associated with other defects.

 

[sanj238]

Thanks guys.

I'm sorry to bring this up again, but I got to make sure that I know this stuff for sure.

So let's say we got a question that says a patient's tongue was deviated to the left. So basically this could be either left LMN CN12 lesion or (right) contralateral UMN corticobulbar tract lesion. What kind of clues will be given in the question that would help us differentiate if it's the LMN or UMN lesion?

For facial nerves, as sanj238 mentioned, if half of the face is paralyzed it's the contralateral UMN lesion and if the entire half of the face is paralyzed it's the ipsilateral lesion (Bell's Palsy). I get that, but in case of CN12, what would be the clue to differentiate the UMN and LMN?

just to be clear for facial if it was UMN it would only be the lower half of the face. if it was entire half of the face it is the CN VII.

you would be given UMn and LMN info.

If they really wanted to trick you they wouldnt even describe UMN v LMN for instance they could show you a image of a guy with his forehead wrinkled where the folds on his head would be seen, his eyes would not be closed but his lower mouth would be down on one side. this would mean a UMN lesion.

 

[Apoplexy__]

CN12 passes through the carotid triangle and can be compressed by ectopic thyroid tissue. It was a point of emphasis in our anatomy class.. I guess it's not emphasized anywhere else lol.

Ah, that makes sense. Nah, never heard of that lol.

 

[sanj238]

fc has it

Ah, that makes sense. Nah, never heard of that lol.

 

[ulikedaggers]

fc has it

Do you know what card it's on?

 

[sanj238]

Do you know what card it's on?

I think in the head and neck anatomy either muscles or nerves