Anterolateral System (ALS) & Spinal Trigem. Nuclei

Question 1

What does the Anterolateral System communicate?

Answer 1

Pain, temperature and non-discriminative touch

Question 2

What are the main tracts of the ALS?

Answer 2

Spinothalamic and Spinoreticular

Question 3

The spinothalamic pathway is a ____ pathway

Answer 3

Direct

Question 4

The spinoreticular pathway is a ______ pathway

Answer 4

Indirect

Question 5

Where do the afferent fibers of the ALS pathway enter the spinal cord?

Answer 5

Lateral division of the posterior root

Question 6

Once the afferent fibers of the ALS enter the posterior root, then where do they go?

Answer 6

They either ascend or descend 1-2 levels in the posterolateral tract/fasciculus and then synapse

Question 7

Another name for the posterolateral tract/fasciculus?

Answer 7

Lissauer’s tract

Question 8

Where are the 2nd order neurons located for the ALS?

Answer 8

Posterior horn lamina

Question 9

What lamina layers do the afferent fibers synapse to in the posterior horn?

Answer 9

1,2,3,4

Question 10

What are laminas 3 and 4 called?

Answer 10

Nucleus proprius

Question 11

Where do the 2nd order neurons go for the ALS pathway?

Answer 11

Across the midline using the anterior white commissure to the contralateral ALS

Question 12

Where is the ALS?

Answer 12

Anterior and lateral within the spinal cord

Question 13

As the 2nd order neurons ascend within the ALS, where do they synapse?

Answer 13

VPL of thalamus to 3rd order neurons

Question 14

Where do the 3rd order neurons of the ALS go?

Answer 14

Somatosensory cortex

Question 15

Is the ALS somatotopy the same as the PCML?

Answer 15

NO; they are exact opposites

Question 16

Describe the ALS somatotopy

Answer 16

The medial side of the ALS = upper arm/neck fibers

The lateral side of the ALS = lower extremity fibers

Question 17

What lamina levels do the spinoreticular fibers synapse on to 2nd order neurons at?

Answer 17

2 and 3

Question 18

What is the extra step in the spinoreticular tract?

Answer 18

2nd order neurons synapse at the Reticular Formation (RF)

Question 19

Once the spinoreticular 2nd order neurons have synapsed at the RF, where do the 3rd order neurons go?

Answer 19

To the thalamus and resume normal pathway

Question 20

What is the benefit of the spinoreticular tract?

Answer 20

It adds higher order neural processing of the sensory information = more specific information about the stimulus

Question 21

Blood supply to the ALS?

Answer 21

Arterial Vasocorona and anterior spinal A.

Question 22

What will a lesion of the blood supply to the ALS cause?

Answer 22

Patchy loss of nociception, thermal and touch on the contralateral side of body starting 1-2 segments below where the lesion is

Question 23

Bilateral loss of sensory and motor function at/below site of injury

Answer 23

complete spinal cord injury

Question 24

Some function at or below site of injury

Answer 24

Incomplete spinal cord injury

Question 25

If a patient has sensation and proprioception, but has loss of motor and pain/temp sensation, what syndrome?

Answer 25

Anterior cord syndrome - anterior half (anterior horn and ALS pathways) have been injured but PCML still in tact

Question 26

If a patient has loss of pain and temperature pathways, what is the likely syndrome?

Answer 26

Central cord - damage to anterior white commissure

Question 27

Transient symptoms like numbness, tingling, burning that resolve in 1-2 days

Answer 27

spinal contusion

Question 28

Damage to 1/2 of the spinal cord

Answer 28

Brown-sequard syndrome (hemisection)

Question 29

What is damaged with brown-sequard syndrome?

Answer 29

PCML, ALS, CST pathways

Question 30

Describe the unique sensation result from a brown-sequard syndrome

Answer 30

Loss of touch/pressure/proprioception from the ipsilateral side (PCML) Loss of pain and temperature from the contralateral side 1-2 segments below injury (ALS) Loss of motor function from ipsilateral side (CST)

Question 31

What happens with syringomyelia?

Answer 31

Cyst cavitation in central regions of the spinal cord

Question 32

What is initially damaged with syringomyelia?

Answer 32

Anterior white commissure of ALS

Question 33

As the cyst in syringomyelia accumulates fluid and grows, what region will then be damaged?

Answer 33

Anterior horn of the spinal cord

Question 34

What is the result of syringomyelia?

Answer 34

Bilateral cape pain/temp lost = both arms and shoulders; eventually UE muscle weakness

Question 35

What is the blood supply to the medullary ALS?

Answer 35

PICA - posterior inferior cerebellar A.

Question 36

What is the blood supply to the pons ALS?

Answer 36

Basilar or anterior inferior cerebellar or superior cerebellar

Question 37

What is the result of both medullary ALS lesion and pons ALS lesion?

Answer 37

Contralateral loss of pain/temp.

Question 38

What does the spinal trigeminal nucleus communicate?

Answer 38

Pain, temperature and non-discriminative touch

Question 39

Where does the spinal trigeminal nucleus span?

Answer 39

Obex -> C2,C3

Question 40

What is the main division within the spinal trigeminal nucleus?

Answer 40

Pars caudalis

Question 41

The afferent signals from the trigeminal enter at the level of the midpons, how do the reach the spinal nucleus?

Answer 41

They must descend to synapse to their 2nd order neurons in this nucleus

Question 42

What do the afferent signals descend down to reach the spinal trigeminal nucleus?

Answer 42

Spinal trigeminal tract

Question 43

Once synapsed at their 2nd order neurons in the spinal trigeminal nucleus, what do the 2nd order neurons travel?

Answer 43

Ascend the anterior trigeminothalamic tract

Question 44

Where do the 2nd order neurons travel to once they are in the anterior trigeminothalamic tract?

Answer 44

VPM of thalamus

Question 45

What 2 planes is the spinal trigeminal nucleus somatotopy in?

Answer 45

Anterior -> posterior | Rostal -> caudal

Question 46

Describe the anterior to posterior mapping for the spinal trigeminal nucleus

Answer 46

``` Anteriorly = V1 Posteriorly = V3 ```

Question 47

Describe the rostral to caudal mapping for the spinal trigeminal nucleus

Answer 47

Rostal (near obex) = mouth Middle = midcheek Caudal (near C2,C3) = lateral edges of face near ears

Question 48

Lesions that affect the rostal to caudal ends of the spinal nucleus is referred to as what type of sensory loss?

Answer 48

Onion-peel sensory loss | Sensory loss in layers from mouth back to the ears when going from rostral to caudal in the nucleus

Question 49

Lateral medullary and lateral pontine lesions affect the spinal trigeminal nucleus how?

Answer 49

IPSILATERAL loss of pain and temperature sensation