Anatomy - Spinal Trigeminal Nucleus

Question 1

describe the path of the spinal trigeminal nucleus

Answer 1

afferents enter pons and turn caudally to descend in the spinal trigeminal tract which then becomes continuous with Lissauer’s tract in upper cervical cord

Question 2

what are the three divisions of the spinal trigeminal nucleus and which does the most with pain and temperature sensation to the face

Answer 2

pars caudalis (most inferior, most involved with pain and temperature to face for CN V)
pars oralis
pars interpolaris

Question 3

what is the significance of the spinal trigeminal tract merging with Lassauer’s

Answer 3

it allows for a uniform pain/temp sensation for the face instead of dividing it into distinct sections

Question 4

where is the pars oralis division of the spinal trigeminal nucleus

Answer 4

most rostral part

- extends from main sensory nucleus to pontomedullary junction

Question 5

where is the pars interpolaris located

Answer 5

in the rostral medulla in between pars oralis and pars caudalis
- extends from superior medulla to obex

Question 6

where is the pars caudalis located

Answer 6

from C2, C3 to the obex

Question 7

compare more caudal lesions of the pars caudalis to more rostral lesions

Answer 7

caudal: the more caudal the lesion, the larger the area of sensory loss with the mouth spared
rostral: sensory loss starts at the back of the head and moves forward towards mouth

(onion peel sensory loss)

Question 8

describe the pathway of primary afferents coming in from trigeminal using the spinal nucleus (pain and nociception from face)

Answer 8

primary afferents come in and synapse onto trigeminal ganglion –> enter midbrain and descend along spinal trigeminal tract until reaching pars cadualis –> contacts 2nd order neurons in pars caudalis –> cross contralaterally –> ascend as the anterior trigeminothalamic tract to VPM

Question 9

describe the trigemino-reticulo-thalamic pathway

Answer 9

pain fibers project bilaterally to the reticular formation as trigeminoreticular fibers –> facilitates ascending reticular activating system (ARAS) –> plays and important role in arousal and alertness

Question 10

what kind of info does the pars oralis receive

Answer 10

tactile information from central region of face

Question 11

what kind of info does the pars interpolaris receive

Answer 11

info from peripheral region of face

Question 12

information from the pars oralis and interpolaris go where along with the contralateral thalamus

Answer 12

project fibers to the cerebellum along with the contralateral thalamus

Question 13

sx of a unilateral lesion of the trigeminal

Answer 13

• anesthesia in trigeminal dermatomes
• loss of jaw-jerk reflex
• atrophy of muscles of mastication
• loss of ipsilateral and consensual corneal reflex

Question 14

what is alternating analgesia

Answer 14

where lesions in the upper medulla or lower pons destroys fibers in spinal trigeminal tract and in the medial leminiscus
–> ipsilateral hemianalgesia of face and contralateral hemianalgesia of body

Question 15

what is alternating hemiplegia

Answer 15

lesion causing unilateral destruction of trigeminal nerve and corticospinal tract in the pons
–> causing ipsilateral trigeminal anesthesia and paralysis and contralateral spastic hemiplegia

Question 16

sx of Wallenberg’s and why

Answer 16

contralateral loss of pain and temp of body with ipsilateral loss of pain and temp over face

• damage to the PICA affects ALS and the spinal trigeminal nucleus (ALS controls contralateral pain and temp to the body and trigeminal controls ipsilateral pain and temp to face)

Question 17

describe the corneal reflex

Answer 17

afferent limb: trigeminal
efferent limb: facial

irritating stimulus to cornea –> activates C fibers whose cell bodies are in trigeminal ganglion –> axons descend spinal trigeminal tract –> terminal in spinal trigeminal nucleus in pars caudalis –> en route to VPM fibers are sent to facial motor nucleus –> innervate orbicularis oculi to close eyelids