cranial nerve question

[firstaid2012]

i read somewhere ( i think unless i wrote it in my notes wrong) that cranial nerve 10 lesion if its UMN its uvla deviates toward same side as lesion. and if its LMN uvula deviates to contralateral side ??? can some one please correct/ or explain this to me. what about cranial 12?

please and thank you

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[ijn]

I wouldn't waste any time learning upper motor neuron lesions for cranial nerves with the exception of the facial nerve. Learn the LMN ones. The tongue deviates toward the side of a LMN lesion of the hypoglossal nerve. The uvula deviates away from the side of a LMN lesion of the vagus nerve.

 

[withrye]

I agree that it's best to just think of LMN lesions with those two. The reasoning behind the deviation is the action of the muscle. CNX pulls the uvula up, so when you have an LMN on one side, that side isn't pulling up anymore, meaning the other side pulls the uvula up and to the contralateral side of the lesion.

For CNXII, the story is the same. The hypoglossal nerve acts to push the tongue away from the side innervating it. Therefore, when you lose LMN innervation, the other side is unopposed and can push the tongue toward the lesioned side.