Corticobulbar Tract Flashcards Preview

Med Neuro Block 3 > Corticobulbar Tract > Flashcards

Flashcards in Corticobulbar Tract Deck (13)
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1
Q

Corticonuclear / Corticobulbar Tract:
Function

A
  • Function: Controls muscles of the head and face
2
Q

Where do corticonuclear/corticobulbar fibers originate?

A

Precentral gyrus

3
Q

Corticonuclear fibers pass with corticospinal tract fibers through which structures?

A
  1. corona radiata
  2. internal capsule (area 4 at genu)
  3. cerebral peduncle
4
Q

Corticobulbar Tract Route:

  • Projection:
  • Termination:
A
  • Cerebral cortex
  • Corona radiata
  • Internal capsule
  • Projection: Corticonuclear fibers project through the posterior limb of the internal capsule (closer to genu than CST fibers)
    • ​bilateral
  • Termination: CN motor nuclei
    • ​CNs V, VII (* contralateral)
    • XII (* contralateral)
    • nucleus ambiguus (CNs IX and X)
    • accessory nucleus (CN XI)
5
Q

Describe the precentral gyrus association with the corticospinal tract:

A
  • Precentral gyrus projects in assoc. w/ corticospinal tract to CN motor nuclei in brainstem
    • UMN for brainstem CN nuclei
  • Most of these are corticoreticular fibers:
    • relay information through the reticular formation to CN motor nuclei
  • Those nuclei that receive DIRECT corticobulbar fibers include:
    • trigeminal, facial, and hypoglossal nuclei
6
Q

Describe the corticobulbar pathway to the facial nucleus (left cortex):

A
  1. Left cortex projects to:
    • right lower & upper facial motor nuclei
    • left upper facial motor nuclei
  2. Facial motor nuclei project to their repsective regions:
    • rt. lower facial motor nucleus ⇒ right lower face
    • rt. upper facial nucleus ⇒ right upper face
    • lt. upper facial motor nucleus ⇒ left upper face
7
Q

What would you expect with a cortical or internal capsule lesion?

A
  • simultaneously affect the corticospinal tract and corticonuclear tract
  • patients will exhibit contralateral hemiplegia accompanied by CN signs:
    • CN VII
    • CN XII
8
Q

Peripheral 7th vs Central 7th lesion (left):

A
  1. Peripheral (Bell’s Palsy)
    • ​​Contralateral hemiplegia
    • Affects the entire right side of the face
      • ​Ex: ptosis, drooling, ect.
  2. Central
    • ​​contralateral hemiplegia
    • Affects the lower side of the right face
      • Ex: drooling
9
Q

Why does a central 7th lesion only affect the lower contralateral portion of the face?

A

Consider the left side:

  • the right cortex also contributes directly to the right upper facial motor nucleus
  • Thus, the right upper face is still receiving motor input via the right cortex
    • ​i.e. upper facial muscles receive motor input both ipsilaterally and contralaterally
10
Q

Describe the cotricnuclear pathway to the hypoglossal nucleus (left):

A
  1. Lt. coticonuclear tract projects ⇒ rt. hypoglossal nucleus
  2. Rt. hypoglossal nucleus ⇒ rt. CN XII
11
Q

What are the CN XII signs in a corticonuclear tract lesion?

A
  • deviated tongue away from affected side
    • signals a contralateral corticonuclear lesion
    • Example:
      • lt. tongue deviation indicates a rt. corticonuclear tract lesion
12
Q

What are the CN XII signs in a peripheral CN XII lesion?

A
  • Tongue deviates toward the affect side
    • ipsilateral CN XII lesion
    • Example:
      • rt. CN XII lesion ⇒ rt. sided tongue devation
13
Q

What is pseudobulbar palsy?

A
  • bilateral lesion of corticobulbar tract
    • Dysphagia, dysarthria, paresis of the tongue, loss of emotional control
  • Causes: brainstem infarcts, ALS, MS