Lecture 12: Motor Tracts Flashcards by Spandana Sama

How many neurons are involved in motor tracts?

2: Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN)

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Where are the cell bodies of the UMNs located?

Cerebral cortex or brainstem

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Where are the cell bodies of the LMNs located?

Cell body in spinal cord or brainstem that directly innervates skeletal muscle

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What are examples of LMNs?

Peripheral and motor component of Cranial Nerves

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What is the direct somatic motor pathway?

Cerebral Cortex –> brainstem/spinal cord –> muscle

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What is the indirect somatic motor pathway?

Direct pathway + synapses in brainstem, basal ganglia, thalamus, reticular formation, and cerebellum

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Briefly, how does the corticospinal tract work?

UMN from cortex synapses at LMN at spinal cord, which allows voluntary movement

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What does the medial and lateral corticospinal tract do?

Medial: Postural muscles (not imp)
Lateral: Voluntary movement

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What horn do the UMNs and LMNs of the corticospinal tract synapse?

Ventral

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What part of the internal capsule do the cell bodies of the corticospinal tract travel through?

Posterior limb

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In the corticospinal tract, how do UMN reach LMN?

Leave motor cortex via posterior limb of internal capsule
Descend to middle ⅓ of cerebral peduncle
Travel down anterior pons and medulla
Decussate in pyramids of medulla
Synapse at LMN in spinal cord

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What initiates voluntary movement?

Mostly the primary motor cortex in precentral gyrus
*controls opposite side of the body

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What supplies the cerebral peduncle?

P1 of Posterior Cerebral Artery

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What supplies anterior pons?

Paramedian Branches of Basilar Artery

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What supplies pyramid?

Sulcal Branches of Anterior Spinal Artery

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What supplies the posterior limb of the internal capsule?

Lenticulostriate Artery from Middle Cerebral Artery

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Lesion in the median corticospinal tract would affect what structures? On what side?

Ipsilateral postural muscles

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What are the cranial nerves are influenced by the corticobulbar tract?

5, 7, 9, 10, 11, 12

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What part of the internal capsule does the corticobulbar tract travel through?

Genu

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What is the relationship between the corticobulbar and corticospinal tracts?

Corticobulbar travels medially to corticospinal

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If CN IX is being influenced by the corticobulbar tract, what side is being affected?

Ipsilateral

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What muscles do the medial LMNs in the ventral horn innervate? Lateral?

Medial project to axial muscles

Lateral project to limbs

What tracts do the medial LMNs receive input from?

Tectospinal

Medial vestibulospinal

Medial reticulospinal

Medial corticospinal

Lateral vestibulospinal

What tracts do lateral LMNs receive input from?

Rubrospinal

Lateral reticulospinal

Lateral corticospinal

Which vestibulospinal tract goes to all spinal levels? What side does it innervate?

Lateral Vestibulospinal tract Ipsilateral

Where do the medial vestibulospinal fibers terminate?

T2 to T3 | (innervate neck and shoulder muscles)

Which reticulospinal tract innervates postural muscles and limb extensors? What side?

Medial reticulospinal (pontine) Ipsilateral

What neurons do the lateral (medullary) reticulospinal tract facilitate and inhibit?

Facilitates flexor motor neurons Inhibits extensor motor neurons

What does the rubrospinal tract innervate?

Upper limb flexors

What tract is involved with visual reflexes to auditory stimuli?

Tectospinal

Patient presenting with flaccid paralysis, muscle atrophy, hyporeflexia, and hypotonia or fasciculations probably has a lesion where?

Lower motor neurons

What tract is lost in UMN syndrome?

Corticospinal tract (direct) Loss of regulation from indirect pathway

In an UMN lesion, what is overactive and what is underactive?

Overactive: Muscles - hypertonic, spastic (collapse of resistance at end of ROM), hyperreflexia Underactive: distal extremity strength

What side and level would LMN lesion signs manifest?

Ipsilateral at the level of the lesion

Where would a UMN lesion have contralateral and ipsilateral clinical signs?

Contralateral - Above lower medulla (where corticospinal tract crosses) Ipsilateral - Spinal cord

If UMN is lesioned, where do the clinical signs manifest?

Below level of lesion

If a patient has decorticate posturing, where is the lesion?

Above the level of the red nucleus (UMN)

In decerebrate posturing, what nuclei is the lesion located between?

Below red nucleus, above reticulospinal and vestibulospinal

After suffering an injury to the spinal cord, a patient initially shows +1/4 DTRs. After a period of a couple weeks, pt shows +4/4 DTRs. What disorder does he have? What has been lesioned?

Spinal shock Corticospinal tract (appears as a UMN lesion)

Patient presents with hemiparaplegia on the ipsilateral side and hemianesthesia on the contralateral side. What syndrome is this and what has been lesioned?

Brown Sequard's Syndrome UMN of the CST, Dorsal column, spinothalamic tract

In a syringomyelia, what is affected if that pt has LMN signs?

Ventral horns

In a syringomyelia, what is affected if that pt has UMN signs?

Lateral corticospinal tract

Patient with ipsilateral flaccid paralysis and hyperreflexia, contralateral loss of pain and temperature sensation. However, vibratory sense is intact. You suspect that the anterior spinal artery has been hit. What syndrome is this?

Anterior cord syndrome

Patient presents after MVC where he was rear-ended. Pt states he doesn't have a headrest and his head "flew back". The patient complains of loss of motion in the arms and hands. What syndrome might he ahve?

Central cord syndrome

What structures are lost in lateral medullary syndrome?

Spinothalamic tract (ALS) Spinal trigeminal nucleus/tract Nucleus ambiguus vestibular nuclei Inferior cerebellar peduncle

Dejerine syndrome can be brought on by occlusion of what artery?

Anterior spinal A.

What structures are lost in medial medullary/Dejerine syndrome?

Pyramids Medial lemniscus CN 12 nucleus

What tract is lesioned in central 7 palsy? What nucleus?

Corticobulbar tract Lower facial motor nucleus

Where is the lesion in Weber Syndrome? What structures are affected?

Midbrain Corticospinal tract Corticobulbar tract CN 3

What neurons are affected in amyotrophic lateral sclerosis?

Somatic motor neurons (both UMNs and brainstem/SC LMNs)

Progressive loss of sensory and motor function in the hands and feet towards the body may be a sign of what disorder?

Polyneuropathy

Patient presents with ataxia, vertigo, loss of pain/temp to the R face but loss of pain/temp to the L arm. What syndrome is this patient suspicious for? What artery may be occluded?

Lateral Medullary/Wallenberg's syndrome PICA

Pt presents with R sided loss of proprioception, vibratory loss, as well as R arm flaccid paralysis. Also presents with L tongue deviation. What is this patient suspicious for?

Medial medullary/Dejerine syndrome

Pt presents with R lower face droop, flaccid paralysis of the R arm, as well as R tongue deviation and L uvula deviation. Upon eye examination their R eye is dilated. What syndrome might this patient have?

Weber