12. Motor Tracts (Keim) Flashcards by Liz Pennington

What are the signs for upper motor neuron damage?

Upper
- Hyperreflexia
- Babinski
- Loss of strength and dexterity
- Spasticity
- Rigidity
- Pronator Drift

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What are the signs for lower motor neuron damage?

Lower
- Flaccid paralysis
- Muscle wasting
- Hyporeflexia / areflexia
- Denervation hypersensitivity or fasciculations

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What is the orientation of proximal / distal and flexors vs extensor fibers in the anterior horn?

The proximal motor neurons (trunk) are more medial, and distal motor neurons are more lateral.

Also flexors are more posterior, and extensors are more anterior.

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What are the two lateral indirect upper motor neuron pathways?

What is significant about indirect pathways?

Rubrospinal tract

Lateral reticulospinal tract

tonically activate antigravity and axial LMNs

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What is the function of the medial vestibulospinal tract?

starts

ends

coordination of head movement

mid/lower vestibular nuclei in medulla

cervical and thoracic levels (neck/shoulder m.)

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What is the function of the lateral vestibulospinal tract?

starts

ends

faciliation of extension against gravity

vestibular nuclei in pons

IL LMN for postural muscles and limb extensors

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What is the function of the tectospinal tract?

Starts:

Ends:

Turns one’s head toward sound and pointing the head where the eyes are pointed.

Superior Colliculus

Neck Muscles

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What is the function of the lateral/medullary reticulospinal tract?

Starts:

Ends:

facilitates flexor motor neurons and modulates extesor mechanisms ipsilaterally.

Inhibits spinal segmental reflexes

medullary reticular formation

flexors/extensors

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What is the function of the rubrospinal tract?

starts

ends

facillitation of the upper limb flexors contralaterally.

red nucleus

CL upper limb flexors

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Where do the fibers of the lateral corticospinal tract arise from?

Primary motor cortex

Supplementary motor area

Premotor cortex

ALSO

Primary somatosensory cortex

Parietal association cortex

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What is the path of the fibers of the lateral corticospinal tract pathway from cortex to spinal cord?

Cortex

Posterior limb of internal capsule

Midbrain in the middle 1/3 of the cerebral peduncles.

Pons

Pyramids in the medulla

Decussation of pyramids

Lateral column of the spinal cord

Synapse with LMN in the ventral horn of the spinal cord.

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What is the somatotopic organization of the fibers from the lateral corticospinal tract as they pass through the posterior limb of the internal capsule?

Same as the anterolateral system

The lower fibers are more lateral (posterolateral to be precise)

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What arteries supply the internal capsule?

Lenticulostriate arteries off the middle cerebral A.

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What artery supplies the corticospinal tract in the midbrain?

In the pons?

In the medulla?

Corticospinal tract arteries:

Midbrain – posterior cerebral A. (P1)

Pons – paramedian branches of basilar A.

Medulla – sulcal branches of anterior spinal A.

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What motor nuclei are present in the pons?

5, 6, 7

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What motor nuclei are present in the midbrain?

3, 4

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What motor nuclei are present in the medulla?

IX, X (nucleus ambiguus)

XII

(9, 10, 12)

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Differentiate between Central Seven and Bell’s Palsy

Why does Central Seven show the distribution that it does?

Central Seven only has lower facial dropping on the contralateral side of lower face (lesion rostral to facial motor nucleus of corticobulbar tract)

Bell’s Palsy has upper and lower facial drooping on the ipsilateral side (CN VII)

The forehead gets bilateral input from the corticobulbar tract, while CN VII innervates contralateral sides of the lower face only (no bilat. input there)

Medial Medullary Syndrome

What A. involved?

What structures affected?

What sx?

AKA Dejerine Syndrome

ASA-sulcal branches

pyramid, medial lemniscus, CN XII

Contralateral hemiplegia (UMN)

contralateral loss of prop./vib/touch to body

Deviation of tongue TOWARD lesion (LMN)

What is lateral medullary syndrome?

What A. is involved

What structures are hit

If it’s in the pons:

If it’s in the medulla:

what are the sx ?

AKA Wallenberg Syndrome

PICA

ALS, Spinal Trige. Tract and nucleus

CN VI and VII involvement

LMN IX/X

loss ot temp/pain to CL body

loss of temp/pain to IL face

hoarse voice, K sound is hard to make, dysphagia (Medulla), or abducens/facial deficits (pons), IL Horner’s

Central Cord Syndrome

What is it?

What are the symptoms?

Basically same as Syringomyelia symptom-wide

compression and damage to central portion of spinal cord

MOI: cervical hyperextension

Anterior Cord Syndrome

What is it?

What are the sx?

compression/damage to anterior part of spinal cord due to damage of the ASA (infarct), IV disc herniation, or radiation myelopathy

Bilateral LMN at the level and and UMN below the level

LMN topographically organized how?

All in anterior horn

Flexors in the back

Extensors in the front

distal limbs out in lateral

proximal axials in medial

Syringomyelia

What causes it?

What is affected sensation-wise?

What is affected motor-wise?

What congenital disease is it associated with?

formation of cysts within the spinal cord in the central canal commonly at C4-ish but can form anywhere

pain and temp affected in cape pattern (AWC hit first)

LMN signs if ventral horns affected

UMN if Lateral Corticpspinal tract is affected (arms first)

typically associated with Chiari I

Brown-Sequard Syndrome What type of lesion is this? What is affected What are the s/s

Hemisected spinal cord ALS, PCMLS, LMN, UMN * CL pain/temp loss 2-3 levels below lesion (due to Lissaur's tract) * IL discriminative touch and proprioception * IL LMN flaccid paralysis @ level of lesion * IL UMN below level of lesion (babinski, weakness, spasticity, etc)

Complete Transection of the Spinal Cord What is affected? What s/s?

ALS, PCMLS, UMN, LMN all sensation is gone 1-2 levels below lesion bilaterally. Loss of bowel/bladder control Initial spinal shock, loss of reflexes, LMN sx @ level ~6wks later UMN BELOW level show Note that LMN s/s will mask any other s/s since it is the most "downstream"

Describe s/s of a lesion in the cortex, internal capsule or cerebral peduncles BEFORE the pyramidal decussation

Affects Corticospinal (arms and legs) and Corticobulbar (face) CL UMN issues CL facial droop

Describe a lesion below the pyramidal decussation?

Affects Corticospinal Tract (arms and legs) IL s/s LMN sx will mask any UMN sx

What does decorticate posturing/rigidity look like? What causes it?

tucked thumb, flexed fingers, fist, pronated forearm, flexed elbow, LE extension and inverted foot Lesion is ABOVE the level of the red nucleus ( midbrain) lesion likely in diencephalon or telencephalon Why? Red nucleus houses rubrospinal tract which allows us to flex

What causes Decerebrate Posturing/rigidity? What does it look like? What tracts are still intact? What other pathology can cause this?

Lesion BELOW red nucleus/including it, but ABVE reticulospinal and vestibulospinal nuclei UE in pronation and extensino and LE in extension reticulospinal and vestibulospinal intact; CST and CBT damaged Can be caused by transtentorial herniation

Rule of thumb for localizing lesions of UMN

above lower medulla (where CST crosses) signs will be CONTRALATERAL In spinal cord, signs will be IPSILATERAL

Sx of LMN lesions

"think floppy" flaccid paralysis wasting/atrophy hyporeflexia hypotonia denervation hypersensitivity/fascicullations

Sx of UMN Syndrome

CST deficit: loss of distal extremity strength and dexterity babinski UMN Lesion: hypertonia/spasticity Basal Ganglia disease: Rigidity Hyperreflexia with/without clonus clasp-knife pronator drift

What is the function of the medial/pontine reticulospinal tract? Starts: Ends:

Facilitation of IL postural reflexes pontine reticular formation IL LMN in postural muscles and limb extensors

What is the function of the corticobulbar tract? What is the function of the Corticospinal tract

control of muscles of the face, chewing, speech and swallowing fine motor control of hand, motor neuron recruitment to increase force, inhibition of postural reflexes

Where do the medial LMNs receive input from?

tectospinal tract medial vstibulospinal tract medial reticulospainl tract medial corticospinal tact lateral vestibulospinal tract All located in anterior funiculus

Where do Lateral LMNs receive input from?

rubrospinal tract lateral reticulospinal tract lateral corticospinal tract Know locations for downstairs

Describe a lesion above the pons in the CBT

MoM no effect Forehead okay bilaterally Lower face droop CL

Describe a CBT lesion in the Medulla A CBT lesion in the spinal cord will have

CL palate weak uvular deviation toward lesion tongue deviation toward lesion

Describe the corticobulbar tract

UMN arises from ventral part of cortical area 4 and descends into brainstem innervating these CN LMN 5, 7, 9, 10, 11, 12 (NO EYEs) axons will cross and control contralateral side except 11

describe the corticobulbar tract pathway

descend through genu of internal capsule passes thru the 3Ps: cerebral Peduncles, anterior Pons, Pyramids stops at specific motor nucleus Cross and pyramidal decussation

What artery supplies the posterior limb of the internal capsule? What happens if it's occluded?

lenticulostriate A. (main) with some from anterior choroidal A. Can lose motor, sensory and vision

Describe the Corticospinal Tract Pathway

cell bodies in cortex descend though posterior limb of internal capsule passes through 3P: cerebral peduncles, anterior Pons, Pyramids, cross at pyramids in lower medulla descend in lateral column called LCST synapse with LMNs in anterior horn of SC \*\*sends collaterals to indirect pathways\*

the somatotopic organization of the internal capsule is set up in such a way that the arms are closes to the ___ and the legs are closes to the \_\_\_

genu; back of the posterior limb (all technically in the posterior limb