Corticospinal System Flashcards
What is plegia?
Plegia – paralysis
– Paraplegia – paralysis of legs
– Quadriplegia – paralysis of all limbs
– Hemiplegia - paralysis of one side of the body
What is paresis?
• Paresis -muscular weakness caused by nerve damage or disease; partial paralysis
– Hemiparesis - muscular weakness on one side of the body
What is paresis?
• Paresis -muscular weakness caused by nerve damage or disease; partial paralysis
– Hemiparesis - muscular weakness on one side of the body
The corticospinal tract is also called…
The pyramidal tract
What is the primary motor cortex?
Lateral corticospinal and corticobulbar tracts arise integrally from the primary motor cortex
– Precentral gyrus
– Anterior paracentral lobule
Describe the somatotropic organization of the primary motor cortex
Cells controlling particular bodily regions aggregate to allow a cohesive bodily mapping(homunculus)
What is the output of of the primary motor cortex?
Pyramidal cells in layer 5 (internal pyramidal layer) communicate directly or indirectly (via interneurons) with lower motor neurons
– Brainstem
– Spinal cord
What are the inputs of the primary motor cortex?
- 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)
What are the subcortical influences on motor cortex?
• Thalamus permits regulation of motor cortex by basal ganglia and cerebellum
Whhat are the roles of the primary and premotor cortices
- Medial premotor (supplementary) areas involved in planned sequences (see figure)
- Lateral premotor areas involved in sensory-guided movements
Where does. The corticospinal and corticobulbar tract start?
Start
• Cerebralcortex
– Primary motor area
• Brodmann’s area 4
What is the route of the corticospinal and corticobulbar tract?
Corona radiata
Internal capsule
Crus cerebri
Pons
What is the route of corticospinal and corticobulbar tract?
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.
What is the route of the crus cerebri f9r the corticospinal and corticobulbar tract?
Corticospinal fibers are within the middle three fifths of the crus cerebri.
Corticobulbar fibers are located medial to the corticospinal fibers.
Where does the corticobulbar tract terminate?
The corticobulbar tract terminates in the brain stem by synapsing on the various cranial nerve nuclei.
Summarize the start, end and function of the corticobulbar tract
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.
What does the corticospinal tract do in the spinal cord?
The corticospinal tract continues into the spinal cord.
What is the significance of lateral corticospinal tract?
• 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
Give a route summary of the lateral corticospinal tract
- 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)
What are the general manifestations of upper motor neuron lesions?
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
What are the corticospinal fibers scenarios that lead to ipsilateral and contralateral signs?
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.
What is the impact of upper motor neuron lesions?
Lesion above (rostral to) decussation: – Signs contralateral to the lesion
Lesion below (caudal to) the decussation: – Signs ipsilateral to the lesion
What is the lower motor neuron signs ?
Lower Motor Neuron Signs • Hyporeflexia • Hypotonia • Fasciculations • Fibrillations • Flaccid Paralysis • Profound atrophy/wasting
Signs is ipsilateral to the lesion
What is Brown Sequard Syndrome?
- 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)
What are the symptoms of corticospinal tract for UMN syndrome?
Ipsilateral below the lesion
-Upper Motor Neuron Syndrome
(UMN – Syndrome):
- Hyperreflexia
- Extensor plantar reflex
- Spastic paralysis
What happens to movements contralateral below the lesion?
No impairments
Explain LMN for the corticospinal tract
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
Who was christopher reeve?
- 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
What is the impact of spinal cord transection?
• Spinal cord transection results in loss of muscle function, visceral and somatic sensation below the level of injury
Describe bilateral spinal cord injury
Bilateral Spinal Cord Injury
-Bilateral Upper Motor Neuron Syndrome below the lesion
(UMN – Syndrome):
- Hyperreflexia
- Extensor plantar reflex
- Spastic paralysis
What are the clinical features of paraplegia?
– 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
What is the significance of infarction in internal capsule?
Upper motor neuron syndrome (contralateral)
– Hyperreflexia
– Extensor Plantar Reflex
– Spastic Paralysis
