Descending Motor pathways

Question 1

What do LMN lesions lead to ?

Answer 1

1) Muscle Wasting
2) Muscle Weakness
3) Hypotonia
4) Absent tendon reflexes
5) Fasciculations

Question 2

What is the pyrimidal system?

Answer 2

There are 4 desending pathways which work together to provide movement.

This is the pyramidal system

Question 3

What would happen if only the corticospinal tract was damaged?

Answer 3

1) Intially
- flaccid paraysis of limbs.
- Loss of tendon reflexes

2)inability to carry out fine movements of hands and feet.

Question 4

How is the posterior limb of the internal capsule mapped?

Answer 4

Face (nearest to genu)
Arm
Trunk
Leg

Question 5

Describe the structures through which the corticospinal pathway goes through?

Answer 5

1) Pre central gyrus
2) Posterior limb of internal capsule
3) Cerebral peduncle of midbrain
4) Front of Pons
5) Open medulla pyramids
6) Closed medulla pyramidal decussation
7) Lateral corticospinal tract in spinal cord.
8) Synapse in ventral Grey horn of spinal cord.
9) LMN leaves as ventral rootlets to form spinal nerve.

OR
10% UMN stays on same side goes down Ventral corticospinal tract. crosses over at level of spinal cord.

Question 6

What is the role of the corticobulbar pathway?

Answer 6

Influence LMN in cranial nerve motor nuclei

Question 7

Where do the facial LMNs exit the braintsem?

Answer 7

cerebellopontine angle

Question 8

Innervation of the cranial nerve LMNs is bilateral apart from a couple of exceptions. What is this and can you describe how it is innervated?

Answer 8

1) Facial nucleus.
- The UPPER portion of the face recieves BI-LATERAL innervation.
- The LOWER portion of the face recieves CONTRALATERAL innervation.

2) HypoGlossal Nucleus,
- Only recieves CONTRALATERAL innervation.

Question 9

What would be the effecto of an UMN lesion of the hypoglossal nucleus vs. a LMN lesion of the hypoglossal nerve?

Answer 9

The hypoglossal nucleus is innervated CONTRALATERALLY.

1) Lesion of UMN would mean the the tongue muscle on the opposite side of the lesion would be affect. So the tongue would deviate to the opposite side of the lesion.
2) Lesion of the LMN would men the the tongue muscel on the same side of the lesion is affected so the tongue would deviate to the same side as the lesion.

Question 10

What would be the effect of a LMN lesion of the facial nerve?

Answer 10

Lead to complete facial paralysis on same (ipsilateral side) of lesion

Question 11

What would be the effect of an UMN lesion of the facial nerve (supra nuclear lesion)

Answer 11

The facial nucleus is split into upper and lower face regions.

• upper face is innervated Bi-laterally (from both hemispheres)
• Lower face is innervated unilaterally from the contralateral (opposite) hemisphere.

***Lesion of the UMN would result in lower face paralysis on the contralateral (opposite) side of the lesion. (however Upper face not effected as it would still recieve inneravation from the side with no lesion)

*paralysis of whole side of face indicates damage to LMN facial nerve on same side.