Corticospinal System

Question 1

What is plegia?

Answer 1

Plegia – paralysis
– Paraplegia – paralysis of legs
– Quadriplegia – paralysis of all limbs
– Hemiplegia - paralysis of one side of the body

Question 2

What is paresis?

Answer 2

• Paresis -muscular weakness caused by nerve damage or disease; partial paralysis
– Hemiparesis - muscular weakness on one side of the body

Question 2

What is paresis?

Answer 2

• Paresis -muscular weakness caused by nerve damage or disease; partial paralysis
– Hemiparesis - muscular weakness on one side of the body

Question 3

The corticospinal tract is also called…

Answer 3

The pyramidal tract

Question 4

What is the primary motor cortex?

Answer 4

Lateral corticospinal and corticobulbar tracts arise integrally from the primary motor cortex
– Precentral gyrus
– Anterior paracentral lobule

Question 5

Describe the somatotropic organization of the primary motor cortex

Answer 5

Cells controlling particular bodily regions aggregate to allow a cohesive bodily mapping(homunculus)

Question 6

What is the output of of the primary motor cortex?

Answer 6

Pyramidal cells in layer 5 (internal pyramidal layer) communicate directly or indirectly (via interneurons) with lower motor neurons

– Brainstem
– Spinal cord

Question 7

What are the inputs of the primary motor cortex?

Answer 7

• Primary somatosensory cortex (Brodmann’s areas 3,1,2)
• Premotor areas (programmed responses to sensory input or plans)
• Posterior parietal cortex (Brodmann’s areas 5 and 7) integrates sensory information for motor planning in concert with premotor areas
• Visual and auditory centers
• Limbic and prefrontal areas
• Basal ganglia (via thalamus and premotor area)
• Cerebellum (via thalamus)

Question 8

What are the subcortical influences on motor cortex?

Answer 8

• Thalamus permits regulation of motor cortex by basal ganglia and cerebellum

Question 9

Whhat are the roles of the primary and premotor cortices

Answer 9

• Medial premotor (supplementary) areas involved in planned sequences (see figure)
• Lateral premotor areas involved in sensory-guided movements

Question 10

Where does. The corticospinal and corticobulbar tract start?

Answer 10

Start
• Cerebralcortex
– Primary motor area
• Brodmann’s area 4

Question 11

What is the route of the corticospinal and corticobulbar tract?

Answer 11

Corona radiata
Internal capsule
Crus cerebri
Pons

Question 12

What is the route of corticospinal and corticobulbar tract?

Answer 12

The corticospinal fibers pass through the posterior limb of the internal capsule.

-The fibers that originated form the lateral aspect of the cortex are now medial and vice versa.

The corticobulbar fibers pass through the genu.

Question 13

What is the route of the crus cerebri f9r the corticospinal and corticobulbar tract?

Answer 13

Corticospinal fibers are within the middle three fifths of the crus cerebri.

Corticobulbar fibers are located medial to the corticospinal fibers.

Question 14

Where does the corticobulbar tract terminate?

Answer 14

The corticobulbar tract terminates in the brain stem by synapsing on the various cranial nerve nuclei.

Question 15

Summarize the start, end and function of the corticobulbar tract

Answer 15

Start: Cerebral cortex (lateral aspect of the primary motor area)

End: nuclei motor cranial nerves (brainstem)

Function: Voluntary control of the muscles of the head and neck muscles.

Question 16

What does the corticospinal tract do in the spinal cord?

Answer 16

The corticospinal tract continues into the spinal cord.

Question 17

What is the significance of lateral corticospinal tract?

Answer 17

• Most of the corticospinal fibers (90%) decussate in the medulla forming the lateral corticospinal tract

• The clinically less significant
anterior corticospinal tract is formed by the uncrossed fibers.

    -A minority of corticospinal fibers will terminate in the dorsal spinal gray matter, to presumably regulate sensory input

Question 18

Give a route summary of the lateral corticospinal tract

Answer 18

• Cortex
• Corona radiata
• Internal capsule (posterior limb)
• Crus cerebri
• Basilar pons
• Pyramid (Decussation)
• Spinal cord
• Synapses on alpha and gamma motor neurons in spinal ventral horn (spinal gray)

Question 19

What are the general manifestations of upper motor neuron lesions?

Answer 19

Upper Motor Neuron Signs
• Hyperreflexia
• Extensor Plantar Response
• Clonus
• Hypertonia
• Spastic paralysis
• Disuse atrophy

Spinal shock occurs with bilateral damage to the spinal cord
– Initial lower motor neuron symptoms
– Upper motor neuron symptoms are seen about 4 weeks after injury

Question 20

What are the corticospinal fibers scenarios that lead to ipsilateral and contralateral signs?

Answer 20

Lesions above the decussation will give symptoms on the left side.
Signs are contralateral to the lesion.

Lesions below the decussation will give symptoms on the left side.
Signs are ipsilateral to the lesion.

Question 21

What is the impact of upper motor neuron lesions?

Answer 21

Lesion above (rostral to) decussation: – Signs contralateral to the lesion

Lesion below (caudal to) the decussation: – Signs ipsilateral to the lesion

Question 22

What is the lower motor neuron signs ?

Answer 22

Lower Motor Neuron Signs
• Hyporeflexia
• Hypotonia
• Fasciculations
• Fibrillations
• Flaccid Paralysis
• Profound atrophy/wasting

Signs is ipsilateral to the lesion

Question 23

What is Brown Sequard Syndrome?

Answer 23

• Due to spinal hemisection
• Traumatic and nontraumatic causes
• Clinical manifestation is due to damage to 2 ascending tracts and 1 descending tract on 1 side of the spinal cord.

• These tracts are
– Corticospinal tract (descending/motor)
– Spinothalamic tract (ascending/sensory)
– Dorsal Column – Medial Lemniscus System (ascending/sensory)

Question 24

What are the symptoms of corticospinal tract for UMN syndrome?

Answer 24

Ipsilateral below the lesion
-Upper Motor Neuron Syndrome

(UMN – Syndrome):

• Hyperreflexia
• Extensor plantar reflex
• Spastic paralysis

Question 25

What happens to movements contralateral below the lesion?

Answer 25

No impairments

Question 26

Explain LMN for the corticospinal tract

Answer 26

Yes, LMN’s are lesioned in the ventral horn of the spinal cord:

  -LMN –Syndrome at the level of the lesion

LMN –Syndrome

• Hypo- or areflexia
• Wasting of muscles - Flaccid paralysis
• Fasciculations
• Fibrillations

Question 27

Who was christopher reeve?

Answer 27

• Successful actor, director, producer, and writer.
• Movie ‘Superman’ 1978
• On May 27, 1995 paralyzed from the neck down (quadriplegia) after being thrown from his horse
• Became an advocate for stem cell research
• Died 2004 from heart failure

Question 28

What is the impact of spinal cord transection?

Answer 28

• Spinal cord transection results in loss of muscle function, visceral and somatic sensation below the level of injury

Question 29

Describe bilateral spinal cord injury

Answer 29

Bilateral Spinal Cord Injury
-Bilateral Upper Motor Neuron Syndrome below the lesion

(UMN – Syndrome):

• Hyperreflexia
• Extensor plantar reflex
• Spastic paralysis

Question 30

What are the clinical features of paraplegia?

Answer 30

– flaccid paralysis below the level of the lesion, followed by
development of spasticity (approx. 4 weeks) = spinal shock

– Upper motor neuron signs are seen after this time

– Loss of all somatosensory perception below the lesion

Question 31

What is the significance of infarction in internal capsule?

Answer 31

Upper motor neuron syndrome (contralateral)
– Hyperreflexia
– Extensor Plantar Reflex
– Spastic Paralysis