Exam #2: Corticonuclear Projections

Question 1

Which cranial nerves contain motor projections?

Answer 1

V, VII, IX, X, XI, XII

Question 2

What cranial nerves are involved in the movement of the eyes?

Answer 2

III, IV, VI

Question 3

What are corticonuclear projections?

Answer 3

Axons that arise from neurons in the sensory & motor cortex that synapse with cranial nerve motor nuclei

Question 4

Specifically, which areas of the brain give rise to axons that form the corticonuclear tract?

Answer 4

Precortical motor areas=

• SMA= Brodmann’s area 6
• PMC= Brodmann’s area 6

Primary Motor Cortex= Brodmann 4

Primary Somatosensory Cortex= Brodmann 3, 1, 2

Question 5

What is the general function of the corticonuclear tract?

Answer 5

Production of voluntary movement in the face & head

Question 6

What are the parts of the internal capsule?

Answer 6

Anterior limb
Genu
Posterior limb

Question 7

Where does the corticonuclear tract course through the internal capsule?

Answer 7

1) Corona Radiata
2) Internal Capsule
- Genu & then shifts to the anterior aspect of the PL next to the corticospinal tract

Question 8

What structures do the lenticulostriate arteries supply?

Answer 8

• Internal capsule

- Basal Ganglia

Question 9

What will an occlusion of the lenticulostriate arteries result in?

Answer 9

Extensive motor & sensory deficits of contralateral side of the body

Question 10

Outline the path of the corticonuclear tract.

Answer 10

1) Layer V of the Cortex
2) Corona Radiata
3) Genu–> Posterior limb of the Internal Capsule
4) Termination at cranial nerve motor nuclei in the:
- Pons (V & VII)
- Medulla (Nucleus ambiguous= IX, X, XI)
- Cervical spinal cord

Question 11

Where do the corticonuclear tracts synapse with the Trigeminal nerve? What do the axons of the trigeminal nerve motor nucleus innervate?

Answer 11

• Caudal pons

- Form the roots of the motor branch of the trigeminal nerve that innervates muscles of mastication

Question 12

Where is the facial nuclues located? What are the two parts of the facial nucleus?

Answer 12

• Caudal pons
• Two parts are:
  1) Upper
  2) Lower

Question 13

What does the upper nucleus of the facial nucleus receive?

Answer 13

Bilateral projections i.e. projections from BOTH sides

Question 14

What type of projections does the lower facial nucleus recieve?

Answer 14

ONLY contralateral projections

Question 15

Where do the axons of the upper facial nucleus project?

Answer 15

Upper facial muscles

Question 16

Where do the axons of the lower facial nucleus project?

Answer 16

Lower facial muscles

Question 17

Where does the facial nerve exit the brain?

Answer 17

Stylomastoid foramen

Question 18

What are the neurons of the facial nucleus considered, upper or lower?

Answer 18

Lower Motor Neurons

Question 19

What happens when there is a lesion to the ipsilateral upper motor neuron to the upper facial nucleus?

Answer 19

Minimal changes, mostly asymptomatic

*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; CONTRALATERAL COMPENSATES

Question 20

What happens when there is a lesion to the contralateral upper motor neuron to the upper facial nucleus?

Answer 20

Minimal changes, mostly asymptomatic

*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; IPSILATERAL COMPENSATES

Question 21

What happens when there is a lesion to the contralateral upper motor neuron to the lower facial nucleus?

Answer 21

Weakness of the lower facial muscles on the CONTRALATERAL side

Question 22

What happens when there is a lesion to BOTH of the contralateral upper motor neurons?

Answer 22

Weakness of the lower facial muscles

*This is the basis for differentiating between a stroke & Bell’s Palsy

Question 23

What differentiates a CVA from Bell’s Palsy?

Answer 23

Ability to raise bilateral eyebrows

*****If the patient CANNOT raise both eyebrows–>Bell’s Palsy

Question 24

What arteries supply the facial nucleus?

Answer 24

1) AICA

2) Basilar artery

Question 25

Describe the corticonuclear projections to the nucleus ambiguus.

Answer 25

Bilateral, but predominantly CONTRALATERAL

Question 26

Which way will to uvula deviate when there is a UMN lesion?

Answer 26

To the side of the lesion i.e.

**Lesion to RIGHT corticonuclear fibers innervating the nucleus ambiguous will result in a uvula that deviates TO THE RIGHT

Question 27

What nucleus do the corticonuclear projections to the spinal cord innervate?

Answer 27

Accessory nucleus

Question 28

Corticonuclear projections to the hypoglossal nucleus.

Answer 28

UMN corticonuclear fibers innervate the CONTRALATERAL hypoglossal nucleus

Question 29

Which direction will the protruded tongue deviate when there is a UMN lesion? Why?

Answer 29

Opposite the side of the lesion

• Genoglossus muscle only receives contralateral projections
• B/c of muscle fiber orientation, the normal muscle will push the tongue in the direction of the weak side

Question 30

Where are the eye fields located?

Answer 30

Frontal & Parietal Lobes

Question 31

Outline the path of the projections from the Frontal Eye Fields to CN III, IV, VI.

Answer 31

NOT corticonuclar*****

Instead there are bilateral projections to the reticular formation in the midbrain & pons. These reticular formation fibers then project to the motor nuclei of:

• CN III Oculomotor
• CN IV Trochlear
• CN VI Abducent

Question 32

What is the function of the motor nuclei projects from the frontal eye fields to the motor nuclei of the oculomotor, trochlear, and abducent nerves?

Answer 32

Conjugate eye movement