Exam #6: Corticomotor Function

Question 1

What is the origin, termination, and function of the corticospinal pathway?

Answer 1

Lateral corticospinal tract

• Origin= motor areas of cerebral cortex
• Termination= lateral neurons in ventral horn
• Function= control of distal/ lateral muscles of the body

Anterior corticospinal tract

• Origin= motor areas of cerebral cortex
• Termination= anterior neurons in ventral horn
• Function= control of proximal muscles of the body

Question 2

What is the origin, termination, and function of the corticonuclear (corticobulbar) pathway?

Answer 2

Origin= motor areas of the cerebral cortex 
Termination= muscles of the head & neck 
Function= motor output to muscles of the head and neck

Question 3

What is the origin, termination, and function of the rubrospinal pathway?

Answer 3

Origin= red nucleus 
Termination= same muscles as upper lateral corticospinal tract 
Function= questionable role in arm, hand, and finger movement

Question 4

List the effects of lesions in the corticospinal tract.

Answer 4

1) Weakness

2) Extensor plantar reflex

Question 5

Where is the motor cortex located, and what is its function?

Answer 5

Brodmann 4

- Voluntary movement i.e. implementation of the motor plan

Question 6

Where is the premotor cortex located, and what is its function?

Answer 6

Brodmann 6
- Motor planning and learning activated or guided by external stimuli

*Develops the “motor plan” that is transmitted to the primary motor cortex

Question 7

Where is the supplementary motor area, and what is its function?

Answer 7

This is a subset of nuclei located in Brodmann 6 (premotor cortex)

• Motor planning and preparing for sequential motor acts influenced by internal stimuli
• Coordinates movement between sides of the body
• Anticipatory postural adjustments

*Develops the “motor plan” that is transmitted to the primary motor cortex

Question 8

Where are the frontal eye fields located, and what are their functions?

Answer 8

Brodmann 8

- Influences voluntary and memory guided eye movements

Question 9

Describe the presentation of a lesion to the motor cortex.

Answer 9

A small lesion to the primary motor cortex will produce contralateral weakness without spasticity

Question 10

Describe the presentation of a lesion to the premotor cortex.

Answer 10

Premotor area has a role in visually guided movement e.g. reaching & grasping

Question 11

Describe the presentation of a lesion to the supplementary motor area.

Answer 11

Difficulty initiating or suppressing movement

Question 12

Describe the presentation of a lesion to the frontal eye fields.

Answer 12

• Inability to make saccades not guided by an external target
• Cannot voluntarily direct eyes away from a stimulus

Question 13

What is the difference between an ACA & MCA infarct based on the rough topographical map of the motor cortex?

Answer 13

ACA=

• Leg area of primary motor cortex
• Supplementary motor cortex
• Cingulate gyrus

MCA=

• Trunk, hand, and face area of primary motor cortex
• Premotor area

Question 14

What is quadriplegia? What is tetraplegia?

Answer 14

These are two different terms for the same thing: paralysis of four limbs
- Caused by cervical transection

Question 15

What is paraplegia?

Answer 15

Paralysis of lower two limbs

- Caused by transection below the cervical spine

Question 16

What is paresis?

Answer 16

Weakness to voluntary muscle

Question 17

What is quadriparesis?

Answer 17

Weakness in all four limbs

Question 18

What is hemiparesis?

Answer 18

Weakness in one half of the body (2x limbs)

Question 19

What is monoplegia?

Answer 19

Weakness to one limb

Question 20

Explain the crossed paralysis found with some brain stem lesions.

Answer 20

Crossed paralysis is found in brainstem lesions & produces an “alternating hemiplegia”

Question 21

List the symptoms and signs associated with an upper motor lesion.

Answer 21

Hyperreflexia
Hypertonia
Primitive reflexes

Question 22

List the symptoms and signs associated with a lower motor lesion.

Answer 22

Weakness
Hypotonia
Hyporeflexia

Question 23

Explain the pathophysiology of Brown-Sequard Syndrome.

Answer 23

This is a hemisection of the spinal cord that causes motor and sensory deficit

• No feeling at the level, ipsilateral to the lesion
• DC/ML lost on ipsilateral side
• Pain & temperature lost contralateral
• Monoplegia ipsilateral to the lesion
• Ipsilateral Babinski

Question 24

What are the effects of lesions in the internal capsule (general motor and sensory deficits)?

Answer 24

Loss of motor and sensory contralateral to the side of the lesion

Question 25

What is the effect of lesions of the upper motor neurons in the motor cortices on the control of the upper and lower facial muscles?

Answer 25

UMN lesions result in weakness of the contralateral inferior facial muscles

Question 26

What is the effect of lesions damaging the facial nucleus or the facial nerve?

Answer 26

LMN lesions result in weakness of the contralateral facial muscles

Question 27

What is the difference between superior, middle, and inferior alternating hemiplegia?

Answer 27

Primarily, location of the brainstem lesion

• Superior= midbrain
• Middle= pons
• Inferior= medulla