Contralateral/ Ipsilateral innervation pathways

[tachyon34]

I was always a bit confused by this, and couldnt ever quite figure out neuro problems due to this, but is my understanding correct?



Somatic sensation of pain/temp: contralateral crosses at ant. commissure in the spine
Somatic vibration sense : contralateral, crosses at gracile/fasiculate nuclei
Somatic Motor : contralateral, crosses at pyramidal decussation

Sympathetics: Ipsilateral?

Hardest ones are the CN i never know which ones are ipsilateral or contralateral

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[creamyBokah]

You're right on those first 3. There are some other tracts that handle somatic motor stuff (rubrospinal, vestibulospinal tracts) but the one you have is the main one.

Sympathetics are ipsilateral as far as I can remember (hypothalamus --> hypothalamospinal tract --> T1 --> superior cervical ganglion --> sympathetic stuff).

For CN's, I remember most of them being bilaterally innervated by the corticobulbar tracts but remember that the lower face (lower facial nerve) is only innervated contralaterally and even though the tongue (CN 12) has bilateral innervation, the upper motor neuron principle innervation is contralateral. What this means is that a lower motor neuron injury to CN12 will result in a tongue that protrudes to the ipsilateral side while a UMN injury (maybe stroke to the posterior internal capsule) will result in a tongue that protrudes to the contralateral side.

I think that's all right someone correct me if I'm wrong.

I was always a bit confused by this, and couldnt ever quite figure out neuro problems due to this, but is my understanding correct?

Somatic sensation of pain/temp: contralateral crosses at ant. commissure in the spine
Somatic vibration sense : contralateral, crosses at gracile/fasiculate nuclei
Somatic Motor : contralateral, crosses at pyramidal decussation

Sympathetics: Ipsilateral?

Hardest ones are the CN i never know which ones are ipsilateral or contralateral

 

[killinsound]

I was always a bit confused by this, and couldnt ever quite figure out neuro problems due to this, but is my understanding correct?



Somatic sensation of pain/temp: contralateral crosses at ant. commissure in the spine
Somatic vibration sense : contralateral, crosses at gracile/fasiculate nuclei
Somatic Motor : contralateral, crosses at pyramidal decussation

Sympathetics: Ipsilateral?

Hardest ones are the CN i never know which ones are ipsilateral or contralateral

also, trochlear is the only CN to cross.

 

[tachyon34]

also, trochlear is the only CN to cross.

yea i read that somewhere too, but it seems like some other CN have contralateral innervation like XII and V but i wasnt sure.

 

[hartbot]

my understanding was that the LMNs of trochlear criss-cross in the posterior side of the brain stem. so the right side of the brain controls the right trochlear nerve which actually controls the left eye.

sound right?

 

[Dirt]

yea i read that somewhere too, but it seems like some other CN have contralateral innervation like XII and V but i wasnt sure.

You're thinking of symptoms, for example ipsilateral deviation of the tongue with damage to CN XII, or ipsilateral jaw deviation with CN V damage. Another one is difficulty turning the head away from a lesion of CN XI. The issues here are not whether the innervation is ipsi/contralateral (they are all ipsi), it is what actions the paralyzed muscles have. In the case of CN XI, the ipsilateral SCM turns the head away from the lesion so that is the action that is deficient.

 

[2001bmw330xi]

^^ don't forget Vagus & Uvula deviation!

Vagus lesion contralateral to the side of deviation, but I think it's because of the way the palate pulls on the uvula, not that the vagus fibers actually cross over.

 

[Dirt]

^^ don't forget Vagus & Uvula deviation!

Vagus lesion contralateral to the side of deviation, but I think it's because of the way the palate pulls on the uvula, not that the vagus fibers actually cross over.

Paralyzed levator velli palatini, so the contralateral one is unopposed pulling the uvula away from the broken side

 

[FutureInternist]

Tongue gets PUSHED out so it will deviate towards the weaker side (i.e. L tongue weakness --> tongue deviated to L)
Uvula gets PULLED up so will deviate towards stronger side.

Once you know what side is affected in the periphery you can backtrack to locate the problem in the brain.

 

[tachyon34]

i reread some sections of HY neuro. FOr most CN (except 4) everything from the CN nuclei down the nerve itself is ipsilateral, but the cortical input to the nuclei are from the contralateral hemisphere for some of them (XII, V, lower face VII)