The Corticospinal Tract

Question 1

Motor circuits in the spinal cord are regulated by input from

Answer 1

descending motor pathways:

Question 2

Cortical structures

Answer 2

primary motor cortex
 prefrontal cortex
 somatosensory and parietal association cortex

Question 3

Subcortical structures

Answer 3

basal ganglia
 cerebellum
 thalamus

Question 4

Reflexes

Answer 4

Stereotyped responses to stimuli

Question 5

Voluntary

Answer 5

Goal-directed Internally generated Improve with practice

Question 6

Three types of movement

Answer 6

Reflexes
Voluntary
Automatic Postural Adjustments

Question 7

How many neurons are in the corticospinal tract

Answer 7

one upper motor neuron!

Question 8

The corticospinal tract projects to_______

Answer 8

Lower Motor Neurons LMN in the ventral horn of ALL levels of the spinal cord

Question 9

Function of the corticospinal tract

Answer 9

voluntary movement of the distal extremities

Question 10

Upper motor neuron route of corticospinal tract

Answer 10

corona radiata ­
posterior limb of internal capsule ­
the middle of the cerebral peduncle (crus cerebri) ­
ventral pons
medullary pyramids (pyramidal decussation).
lateral funiculus

Question 11

Where do the fibers of the corticospinal tract decussate adn then what happens

Answer 11

90% of fibers decussate in pyramidal decussation and descend in lateral funiculus to all sp cd levels

Question 12

Description of the corticospinal tract

Answer 12

Primary Motor Cortex connects to alpha lower motor neurons that innervate a particular skeletal muscle via the corticospinal tract (CST).

Question 13

Function of the corticospinal tract

Answer 13

Descends to all spinal cord levels for voluntary control of motor neurons that
innervate muscles in the distal extremities. Allows for skilled movements. Excites flexor m.’s,
inhibits extensor m.’s

Question 14

Lesions ABOVE the pyramidal decussation result in

Answer 14

CONTRALATERAL weakness

Question 15

Lesions BELOW the pyramidal decussation result in

Answer 15

IPSILATERAL weakness bc it has already decussated

Question 16

Upper Motor Neuron (UMN) Lesion:

Answer 16

Paresis (weakness) or paralysis
Spasticity
Hyperreflexia
Loss of abdominal reflexes
Babinski sign

Question 17

What is the babinski sign

Answer 17

stroking the plantar surface of the foot along the lateral border leads to dorsiflexion of the great toe (normal response is plantar flexion) indicative of an upper motor neuron problem

Question 18

Lower Motor Neuron (LMN) Lesion:

Answer 18

Muscle atrophy, Fasciculations, Hypotonia, Hyporeflexia

Question 19

Corticospinal tract lesion: Lesion in the Cortex

Answer 19

Contralateral paresis of a particular body part corresponding to area of cortical damage

Question 20

Corticospinal tract lesion: Lesion in the Posterior Limb of Internal Capsule

Answer 20

Contralateral hemiplegia

Question 21

Corticospinal tract lesion: Lesion in the Cerebral Peduncle (Crus cerebri): Webers syndrome

Answer 21

Weber Syndrome Possible Cause: Occlusion of PCA

Question 22

Corticospinal tract lesion: Lesion in the cerebral peduncle crus cerebral

Answer 22

Contralateral paralysis of lower face, tongue, arm and leg

Question 23

Corticospinal tract lesion: Lesion in the cerebral peduncle crus cerebral CNIII lesion

Answer 23

Ipsilateral oculomotor palsy (eye deviates laterally, ptosis, pupil is dilated and fixed)

Question 24

Lesion in the Medullary Pyramid: Medial Medullary Syndrome

Answer 24

Possible Cause: occlusion of vertebral a. or anterior spinal a.

Question 25

Lesion in the Medullary Pyramid:Corticospinal Tract lesion

Answer 25

Contralateral hemiparesis of arm and leg, face is spared

Question 26

Lesion in the Medullary Pyramid: CN XII injury

Answer 26

Ipsilateral paralysis and atrophy of tongue

Question 27

Lesion in the Medullary Pyramid: Medial Lemniscus injury

Answer 27

Contralateral loss of touch, vibration and joint position sensation from half of the body

Question 28

Lesion in the Spinal Cord

Answer 28

Ipsilateral spastic paralysis Ipsilateral Babinski sign

Question 29

What is a physical sign of an upper motor neuron lesion

Answer 29

Babinski sign

Question 30

the central part of the crus cerebri contains fibers involved in which function

Answer 30

Voluntary movements

Question 31

when CN III emerges from the brainstem, its fibers pass in close proximity to which structure?

Answer 31

Red Nuclei

Question 32

Hoffman’s sign

Answer 32

flick nail of middle finger, index finger and thumb come together in a patient with an upper neuron lesion