Motor Tracts

Question 1

what would a lesion of the corticobulbar tract above the decussation may result in what?

Answer 1

contralateral supranuclear facial palsy

Question 2

what does supranuclear facial palsy present as?

Answer 2

Paralysis of the lower quadrant of the face ( they can’t smile) (contralateral side of lesion)

Question 3

where do corticobulbar fibers originate?

Answer 3

in the head region of the precentral gyrus

Question 4

what part of the internal capsule do the corticobulbar course through?

Answer 4

the genu

Question 5

where does the corticobulbar tract decussate?

Answer 5

in the lower pons

Question 6

what do unilateral lesions of the corticobulbar tract below the decussation result in?

Answer 6

ipsilateral cranial nerve palsies

Question 7

what is apraxia and what is an example?

Answer 7

when a patient cannot perform the motor sequence correctly (brush hair)

Question 8

what are lesions sites that would result in apraxia?

Answer 8

left parietal lobe and premotor cortex

Question 9

what is agnosia?

Answer 9

when a patient can perform a movement but does not know their right from their left

Question 10

what is automatic voluntary dissociation?

Answer 10

when a patient doesn’t know their left from their right, but does a task using their dominant hand

Question 11

what results from ischemia within the territory supplied by the perforating branches of the MCA or ICA?

Answer 11

lenticulostriate infarcts

Question 12

where does the corticospinal pathway originate?

Answer 12

large pyramidally-shaped neurons (cells of Betz) located in the primary motor and premotor cortices

Question 13

where do 85-90% of the corticospinal fibers decussate?

Answer 13

in the lower medulla at the pyramidal decussation

Question 14

what do the corticospinal fibers become after decussation?

Answer 14

the lateral corticospinal tract (LCST)

Question 15

what do the uncrossed fibers of the corticospinal tract continue as?

Answer 15

anterior corticospinal tract (ACST)

Question 16

where in the spinal cord does the LCST descend?

Answer 16

in the lateral funiculus

Question 17

where do most descending motor fibers terminate?

Answer 17

in lower motor neuron pools

Question 18

what do unilateral lesions of the CST result in?

Answer 18

contralateral spastic hemiplegia or spastic hemiparesis (muscle weakness or stiffness on one side)

Question 19

what do unilateral lesions of the LCST result in?

Answer 19

ipsilateral paralysis or paresis of the distal limb musculature innervated by those spinal segments below the level of the lesion

Question 20

where are lower motor neurons found?

Answer 20

in the anterior horn of the spinal cord

Question 21

what do lesions of the LMNs result in?

Answer 21

flaccid paralysis (muscle is completely limp), areflexia, atonia, atrophy, fasciculations

Question 22

what are the signs and symptoms of an UMN lesion?

Answer 22

varying degrees of spastic paresis (weakness) of the axial and proximal limb musculature, hypertonia, hyperreflexia, + babinski sign, clonus, rigidity

Question 23

what is ideational apraxia?

Answer 23

it is a loss of the ability to formulate the ideational concepts necessary to perform a motor activity

Question 24

what are the fibers responsible for a patient’s recovery after a stroke?

Answer 24

corticoreticulobulbar fibers

Question 25

ideomotor apraxia is specifically associated with lesions of what?

Answer 25

the supramarginal gyrus of the dominant hemisphere

Question 26

what do the corticobulbar fibers innervate?

Answer 26

the somatic motor nuclei of the brainstem

Question 27

the facial motor nucleus is divided into two parts. What are they?

Answer 27

an anterior portion of the facial nucleus and a posterior portion of the facial nucleus

Question 28

the anterior portion of the facial nucleus receives corticobulbar fibers from where?

Answer 28

the contralateral cortex

Question 29

what does the anterior portion of the facial nucleus innervate?

Answer 29

the muscles of the lower quadrant of the face

Question 30

the posterior portion of the facial nucleus receives corticobulbar fibers from where?

Answer 30

from both hemispheres of the cortex

Question 31

what does the posterior portion of the facial nucleus innervate?

Answer 31

the upper quadrant of the face

Question 32

where are the most common sites for lesions causing supranuclear facial palsy?

Answer 32

in the facial region of the motor cortex and the genu of the internal capsule

Question 33

what does a central lesion of the facial nerve result in?

Answer 33

Bell’s Palsy

Question 34

unilateral lesion of the corticobulbar fibers to the facial nucleus results in what?

Answer 34

paralysis of the contralateral lower quadrant of the face

Question 35

A lesion of the CST resuts in what?

Answer 35

contralateral spastic hemiplegia