Somatosensory Tracts 2

Question 1

what is the collective system for the pathways that are responsible for relaying pain, temperature and non-discriminative touch?

Answer 1

the anterolateral system

Question 2

what is the largest tract that makes up the anterolateral system?

Answer 2

the spinothalamic tract

Question 3

where do the pain and temperature afferent fibers enter the spinal cord?

Answer 3

the lateral division of the posterior root entry zone (posterolateral fasciculus)

Question 4

after entry, some fibers ascend/descend 1-2 levels in what?

Answer 4

the posterolateral (Lissauer) tract

Question 5

where do the afferent fibers target after entry into the spinal cord?

Answer 5

they target 2nd order neurons in the posterior horn in superficial laminae I and II

Question 6

what is the immediate next step of the second order neuron?

Answer 6

to immediately extend through the posterior horn, cross in the anterior white commissure and then move over to the contralateral side of the spinal cord and join the ALS

Question 7

What is the somatotopic set up of the ALS?

Answer 7

axons from lower levels are found posterolaterally and more rostral levels are added in an anteromedial sequence

Question 8

where do 2nd order neurons go after reaching the contralateral ALS?

Answer 8

they ascend up to the VPL nucleus of the thalamus

Question 9

what kind of fibers are found in the indirect spinothalamic pathway?

Answer 9

spinoreticular fibers

Question 10

what is the main purpose of the spinoreticular pathway?

Answer 10

it contributes to the perception of dull pain and moderates behavioral and motivational changes associated with pain

Question 11

where do the 2nd order neurons travel to after joining the contralateral ALS in the spinoreticular pathway (indirect spinothalamic pathway)?

Answer 11

3rd order neurons in the reticular formation

Question 12

where does the blood supply of the ALS originate from?

Answer 12

the arterial vasocorona and via the sulcal branches of the anterior spinal artery

Question 13

What does occlusion of the blood supply of the ALS result in?

Answer 13

patchy loss of nociceptive, thermal, and touch over the contralateral side of the body, 2 SPINAL SEGMENTS BELOW the lesion

Question 14

what does a complete spinal cord injury result in?

Answer 14

bilateral, total loss of all motor and sensory function at/ below the level of injury

Question 15

what does an incomplete spinal cord injury result in?

Answer 15

some function remains below the primary level of the injury

Question 16

what does an anterior cord syndrome result in?

Answer 16

injury to the motor and pain/temperature pathways in the anterior spinal cord. Patient’s still have proprioception and sensation

Question 17

what does a central cord syndrome result in?

Answer 17

damage to the center of the cord/ anterior white commissure. causes loss of pain/temp pathways, with deficits relative to the size of the lesion

Question 18

what is Brown-Sequard Syndrome?

Answer 18

it is a combination of sensory and motor deficits due to damage to the ALS, PCML, and CST pathways

Question 19

what are the results/symptoms of brown-sequard syndrome?

Answer 19

contralateral deficits: loss of nociceptive, thermal sensation (ALS) approximately 2 segments below the level of lesion; ipsilateral deficits: loss of discriminative tactile, vibratory, and position sense (PCML) at/below the lesion, paralysis of the trunk and extremity (CST)

Question 20

what is the diagnosis of cystic cavitation of central regions of the spinal cord?

Answer 20

Syringomyelia

Question 21

What is the initial damage of a syringomyelia?

Answer 21

to ALS fibers in the anterior commissure

Question 22

How do deficits present for cases of syringomyelia?

Answer 22

cape-like pattern- loss of pain and temperature bilaterally over the arms and shoulders; weakness atrophy, and fasciculations of muscles of the hands

Question 23

What is the trigeminal nuclei responsible for pain, temperature, and non-discriminative touch?

Answer 23

spinal trigeminal nucleus

Question 24

what is the range of the spinal trigeminal nucleus?

Answer 24

obex–> C2/C3

Question 25

what are the three divisions of the spinal trigeminal nucleus?

Answer 25

pars caudalis, pars oralis, pars interpolaris

Question 26

where do the primary afferent fibers for the trigeminal come in at?

Answer 26

the levels of the mid pons

Question 27

what happens after the primary afferent fibers enter?

Answer 27

they descend down to the spinal trigeminal nucleus

Question 28

Once the primary afferent descend and enter into the spinal nucleus, what happens nect?

Answer 28

the second order neurons cross midline within the medulla

Question 29

after crossing within the medulla, what do the second order neurons ascend as?

Answer 29

anterior trigeminothalamic tract

Question 30

where do the second order neurons target after crossing within the medulla?

Answer 30

they target the contralateral VPM nuclei of the thalamus

Question 31

where is the opthalmic dermatome located on the spinal trigeminal nucleus?

Answer 31

anteriorly

Question 32

where is the mandibular dermatome located on the spinal trigeminal nucleus?

Answer 32

posteriorly

Question 33

where do the fibers from right around the mouth terminate on the spinal trigeminl nucleus?

Answer 33

rostrally–> near the obex

Question 34

where do the fibers of the midcheek terminate on the spinal trigeminal nucleus?

Answer 34

the middle segments

Question 35

where do the fibers of the lateral edges of the face terminate on the spinal trigeminal nucleus?

Answer 35

the caudal regions down to C2/C3

Question 36

damage to the spinal trigeminal tract can be described as what type of sensory loss?

Answer 36

onion-peel sensory loss

Question 37

a more caudal lesion of the spinal trigeminal nucleus would result in what?

Answer 37

it spares the oral region, but it affects the posterior and lateral boundaries of the face

Question 38

a more rostral lesion (into the brain stem) of the spinal trigeminal nucleus would result in what?

Answer 38

sensory loss that is increasingly anterior and converges on the mouth

Question 39

what happens when you get a lateral medullary syndrome?

Answer 39

there is an occlusion of the posterior inferior cerebellar artery or branches of the posterior inferior cerebellar artery

Question 40

what happens when you get lateral pontine syndrome?

Answer 40

there is an occlusion of the long circumferential branches of the basilar artery and/or branches of anterior inferior cerebellar artery or superior cerebellar artery

Question 41

what is the reticular formation?

Answer 41

it is a region in the pons

Question 42

What is the vascular supply of the lateral medulla?

Answer 42

PICA (posterior inferior cerebellar artery

Question 43

what would an occlusion of PICA result in?

Answer 43

contralateral loss of pain and thermal sensation

Question 44

what is the vascular supply of the lateral pons?

Answer 44

long circumferential branches of basilar artery and/or branches of anterior inferior cerebellar artery or superior cerebellar artery

Question 45

what would an occlusion of the long circumferential branches of the basilar artery and/or branches of the anterior inferior cerebellar artery or superior cerebellar artery result in?

Answer 45

contralateral loss of pain and thermal sensation

Question 46

what is alternating trigeminal hemiplegia?

Answer 46

unilateral destruction of the trigeminal nerve and CST in the pons

Question 47

what would you expect to see with alternating trigeminal hemiplegia?

Answer 47

ipsilateral trigeminal anesthesia and paralysis as well as contralateral spastic hemiplegia