Motor Tracts

Question 1

Where do upper motor neurons arise and what do they synapse with?

Answer 1

arise and are contained within crebral cortex or brainstem

synapse with LMN or interneurons of the spinal cord

Question 2

Where are the cell bodies of LMNs?

What do they innervate?

Answer 2

in spinal cord or brain stem

synapse w/ skeletal muscle fibers

Question 3

What are the types of LMNs?

Answer 3

gamma motor: medium sized, myelinated –> intrafusal fibers in muscle

alpha motor: large bodies and large myelinated axons –> extrafusal skeletal muscle

Question 4

What part of the internal capsule does the corticospinal tract pass through?

Answer 4

posterior limb

Question 5

Where do fibers cross in the corticospinal tract?

Answer 5

in the pyramids in the lower medulla

90% decussate = lateral corticospinal tract

10% stay ipsi = not clinically significant

Question 6

Where is volontary motor movement controlled?

Answer 6

primary motor cortex (area 4) in precentral gyrus

(R side usually controls left side of body and vice versa)

Question 7

Where do fibers of the lateral corticospinal tract descend in the spinal cord?

Answer 7

lateral column

Question 8

Where do fibers from the cortex controlling the legs and arms end up in the lateral corticospinal tract?

Answer 8

legs –> lateral

arms –> medial

(across from where they are in the cortex)

Question 9

Where do UMNs from the lateral corticospinal tract synapse?

Answer 9

with LMNs in the ventral horn of the spinal cord

Question 10

hemorrhage of what arteries could cause issues with the corticospinal tract?

Answer 10

Lenticulostriate and ant choroidal As –> internal capsule

posterior cerebral A –> crus cerebri of cerebral peduncles

paramedian branches of basilar A –> pyramids of medulla

anterior and posterior spinal As

Question 11

What does the median corticospinal tract control?

Answer 11

postural and proximal movements

don’t cross medulla

only 10% of fibers - isn’t clinically significant

Question 12

Where do UMNs of the corticobulbar tract arise?

where do they go?

Answer 12

ventral part of cortical area 4 –> to brainstem and cranial nerves

axons cross and control muscles on contralateral side

Question 13

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

where does it go to get to the brainstem?

Answer 13

genu

to cerebral peduncles –> anterior pons –> pyramids

Question 14

Where do the axons of the corticobulbar tract cross over?

Answer 14

pyramidal decussation

Question 15

Where are the trigeminal nuclei and how do the UMN run to get there?

Answer 15

anterior pons

50/50 split to either side

Question 16

Where are the facial nuclei and how do UMNs run to get there?

Answer 16

lower anterior pons

lower face muscles: controlled contralaterally

upper face muscles: controlled ipsilaterally

Question 17

What CN nuclei are located in the medulla and how do UMNs of the corticobulbar tract run to get there?

Answer 17

hypoglossal nucleus (12)

nucleus ambiguus (9,10)

contralateral projections

Question 18

Where is the spinal accessory nucleus and how do UMNs from the corticobulbar tract run to synapse there?

Answer 18

in anterior horn of cervical spine

ipsilateral projections

Question 19

Where are LMNs located topographically in the spinal cord?

Answer 19

all in anterior horn

proximal neurons = medial

distal = lateral

flexors = posterior

extensiors = anterior

Question 20

Where do indirect pathways synapse?

Answer 20

brain stem

basal ganglia

thalamus

reticular formation

cerebellum

Question 21

What do medial LMNs receive input from? (5)

Answer 21

tectospinal tract

medial vestibulospinal

medial reticulospinal

medial corticospinal

lateral vestibulospinal

Question 22

What do lateral LMNs receive input from?

Answer 22

rubrospinal

lateral reticulospinal

lateral corticospinal

Question 23

What artery supplies both horns of the sinal cord?

Answer 23

anterior spinal a

Question 24

Where does the lateral vestibulospinal tract run?

Answer 24

lateral vestibular nuclei to spinal cord –> ipsilateral LMNs

innervate postural muscles and limb extensors

(help you extend against gravity)

Question 25

Where does the medial vestibulospinal tract run?

Answer 25

superior, medial, and lateral vestibular nuclei --\> cervical and thoracic levels = neck and shoulder muscles ipsilateral?

Question 26

Where are vestibular nuclei located?

Answer 26

pons

Question 27

Where does the medial/pontine reticulospinal tract run?

Answer 27

pontine reticular formation --\> SC --\> **ipsilateral** LMNs to posteral muscles and limb extensors

Question 28

Where does the rubrospinal tract run?

Answer 28

red nucleus of midbrain --\> SC --\> **contralateral** LMNs to upper limb flexors

Question 29

Where does the lateral reticulospinal tract run?

Answer 29

medullary reticular formation --\> spinal cord --\> **mainly ipsi, some contra** **facilitates flexor** motor neurons and **inhibits extensors**

Question 30

Where doew the tectospinal tract run?

Answer 30

superior colliculus of midbrain --\> upper spinal cord --\> ipsi LMNs to neck muscles --\> visual reflexes to turn head to where eyes and ears are

Question 31

What do you see in LMN lesions?

Answer 31

flaccid paralysis wasting or atrophy hyporeflexia or areflexia hypotonia denervation hypersensitivity = fasiculations (neuron is dying)

Question 32

What do you see in UMN lesions?

Answer 32

loss of distal extremity strength and dexterity **babinski sign** **hypertonia** - spasticity and rigidity **hyperreflexia** - clonus spasticity pronator drift

Question 33

What is rigidity due to?

Answer 33

basal ganglia disease not rate or force dependent

Question 34

What side do LMN lesions cause clinical signs?

Answer 34

same side of lesion!

Question 35

Where do you see clinical signs of UMN lesions?

Answer 35

if lesion is above lower medulla --\> contralateral side if lesion is in SC --\> ipsilateral side

Question 36

What levels do you see clinical signs of spinal cord lesions?

Answer 36

UMN signs **below** level of lesion LMN signs **at level** of lesion

Question 37

What is decorticate posture?

Answer 37

due to lesion **above level of red nucleus** thumb tucked under fingers in fist pronated forarm **flexed arms** extended legs, foot inversion

Question 38

What is decerebrate posture?

Answer 38

due to lesion **below red nucleus, but above reticulospinal and vestibulospinal nuclei** arms **extended**, pronated lower extremity extended

Question 39

What do you see in complete transection of SC?

Answer 39

all sensation lost 1-2 levels below lesion bladder and bowel control lost spinal shock UMN signs **below** lesion LMN signs **at level** of lesion

Question 40

What do you see in hemisection of the spinal cord?

Answer 40

**pain and temp** from **contralateral side** of body lost complete loss of pain 2-3 levels below discriminative touch and proprioception on **ipsilateral side** LMN signs **at level** on ipsi UMN signs **below** on ipsi \***Brown-sequard syndrome**

Question 41

What do you see in syringomyelia?

Answer 41

pain and temp first affected bc of **anterior white commissure** --\> cape pattern If ventral horns affected --\> LMN signs If CST affected --\> UMN signs

Question 42

What syndrome is syringomyelia associated with?

Answer 42

Chiari I

Question 43

What things are damaged in Anterior cord syndrome?

Answer 43

lateral corticospinal tract --\> **UMN ipsi, below** level Anterior horn damage --\> LMN ipsi, at level **Lateral spinothalamic** tract --\> **contra**lateral **pain** and temp lost

Question 44

What things are damaged in central cord syndrome?

Answer 44

\*usually due to cervical hyperextension 1. Ant white commissure affected first --\> bilateral pain and temp lost 2. Ant horn affected --\> LMN loss at level 3. lateral corticopsinal tract --\> UMN loss at level

Question 45

What things are damaged in medial medullary syndrome?

Answer 45

Pyramid medial leminiscus --\> **contra** prop, vibration sense CN 12 nucleus --\> tongue deviates toward lesion

Question 46

Hemorrhage of what A can cause medial medullary syndrome?

Answer 46

anterior spinal a

Question 47

What things are damaged in lateral medullary syndrome?

Answer 47

ALS --\> **contra** loss of pain and temp Spinal trigeminal nucleus and tract --\> **ipsi** loss of pain and temp to face Nucleus Ambiguus --\> 9 and 10 CN loss Inferior cerebellar peduncle --\> ataxia

Question 48

Hemorrhage of what A can cause lateral medullary syndrome?

Answer 48

PICA

Question 49

What is central sevel palsy?

Answer 49

lesion of the corticobulbar tract involving 7th CN If superior to facial motor nucleus: Ms of the upper face are controlled by fibers from both hemispheres --\> **can still wrinkle forehead** Ms of lower face controlled by **contralateral** hemisphere --\> drooping ms at corner of mouth on **contra side**

Question 50

What occurs in Weber syndrome?

Answer 50

lesion of midbrain **CN III** damage --\> **ipsilateral** motor damage (down and out, dilated pupil) contra UMN sx Central 7 sx (contra lower face droop) **uvula** dev to **same side** of lesion (10) **tongue** dev to **opposite** side (12) **ipsi SCM** and Trap paralysis (11)

Question 51

Occlusion of what arteries can cause Weber syndrome?

Answer 51

posterior cerebral A branches of basilar A

Question 52

What is Amyotrophic Lateral Sclerosis?

Answer 52

ALS destroys only somatic motor neurons = **UMNs** and spinal cord **LMNs** paresis, myoplastic hyperstiffness, difficulty breathing, swallowing, and speaking

Question 53

What is polyneuropathy?

Answer 53

damage of nerves: involvement of sensory, motor and autonomic Ns Progresses distal to proximal = stocking/glove pattern (diabetic neuropathy)