Lecture 08 Trigeminal Pathways

Question 1

Describe the course of the precise discriminative tactile information in trigeminal fibers of the face

Answer 1

A few incoming fibers will ascend only in the short ascending root of V and terminate in the main sensory nucleus of V

Question 2

Describe the course of the proprioceptive information in trigeminal fibers

Answer 2

Some of the fibers adjacent to the ascending root course in the mesencephalic tract of V

Coveys the infor to the main sensory nucleus

Question 3

Describe the course of the trigeminal fibers that convey pain (A delta and C) and temperature information from the face

Answer 3

About half of the incoming primary fibers will descend only in the descending root of V
Terminate in the subnucleus caudalis of the descending nucleus of V

Question 4

What nucleus of the V is at the level of the trigeminal nerve?

Answer 4

Main sensory nucleus

Question 5

What information does the Main sensory nucleus of V receive?

Answer 5

precise tactile, crude tactile and proprioceptive information from the face

Question 6

What information from the face terminates in the descending nucleus of V?

Answer 6

All pain and temperature sensations as well as general tactile information from the face

Question 7

What are the three subnuclei of the Descending Nucleus of V?

Answer 7

Subnucleus rostralis
Subnucleus interpolaris
Subnucleus caudalis

Question 8

What information does the Subnucleus Rostralis receive?

Answer 8

Tactile information from the central region of the face

Question 9

What information does the Subnucleus Interpolaris receive?

Answer 9

information from the peripheral region of the face

Question 10

What information does the Subnucleus Caudalis receive?

Answer 10

Pain and temperature information from the anterior 1/2 of the head

Question 11

What is the only nucleus in the CNS that is comprised of pseudo-unipolar neurons?

Answer 11

Mesencephalic Nucleus of V

Question 12

What does the Mesencephalic Nucleus of V convey?

Answer 12

unconscious proprioceptive and pressure information from mm of the head and oral region

Question 13

What does the Trigeminal Motor Nucleus innervate?

Answer 13

muscles derived from mesenchymal cell in the first branchial arch

Located at the same lvl of the brainstem as the main sensory nucleus

Question 14

What is the course of the secondary axons from the subnucleus caudalis?

Answer 14

Decussate and ascend in the trigeminal lemniscus

TL terminates in the ventral posterior medial (VPM) nucleus of the dorsal thalamus

Question 15

What do the tertiary axons from the VPM nucleus travel to?

Answer 15

the primary somesthetic cortex

Question 16

Describe the Trigemino-reticulo-thalamic Pathway

Answer 16

C type pain fibers convey ‘slow’ pain info to subnucleus caudalis
Neurons project bilaterally to the brainstem reticular formation as trigeminoreticular fibers
Diffuse, multi-neuronal pathway-> thalamus

Question 17

What does the trigeminal input into the RF facilitate?

Answer 17

the ascending reticular activating system (ARAS), plays an important role in arousal and alertness

Question 18

What is the fast pain pathway from trigeminal n fibers?

Answer 18

Descending tract of V->Subnucleus caudalis->TL->VPM->1* somesthetic cortex

Question 19

What is another for trigeminal lemniscus?

Answer 19

anterior trigeminothalamic tract

Question 20

What is the crude tactile pathways from the face?

Answer 20

Bifurcate into ascending and descending roots->main sensory nucleus, subnuclei rostralis and interpolaris

Most 2dary fibers decussate and ascend in TL ->VPM
Some remain uncrossed->ipsilateral dorsal central trigeminal tract (DCTT)->VPM

VPM->1* somesthetic

Question 21

Describe the precise tactile pathway from the face

Answer 21

Some Ascend ONLY in short ascending root of V ->Terminate in main sensory nucleus of V

Most->ipsilateral dorsal central trigeminal tract->VPM

Some decussate->TL->VPM

Question 22

What is the trigeminal lemniscus adjacent to as it ascendts?

Answer 22

medial lemniscus in the brainstem

Question 23

Describe the proprioceptive pathways from the face

Answer 23

mesencephalic root of V->Main sensory nucleus->TL and DCTT->VPM->1* somesthetic cortex

Mesencephalic root of V->Some terminate upon alpha motor neurons of trigeminal motor nucleus directly (jaw-jerk reflex)

Question 24

Describe the Jaw-Jerk reflex

Answer 24

Rapid depression of chin

massteric n->mesencephalic nucleus->motor nucleus of V->massteric n->motor end-plate->clenching teeth

Question 25

What trigeminal nuclei are the only ones that project to the cerebellum?

Answer 25

Subnuclei rostralis and interpolaris

Question 26

What information via the trigeminocerebellar fibers through the ipsilateral inferior cerebellar peduncle is conveyed to the anterior vermis?

Answer 26

crude tactile (light touch) from the head

Question 27

What information from the main sensory nucleus via superior cerebellar peduncle is conveyed to the anterior vermis?

Answer 27

precise tactile and proprioceptive info from the head

Question 28

What does unilateral lesion of the trigeminal nerve result in?

Answer 28

anesthesia and loss of general sensations in the trigeminal dermatomes
Loss of jaw jerk reflex
Atrophy of the mm of mastication
Loss of ipsilateral and consensual corneal reflex

Question 29

What is alternating analgesia?

Answer 29

Ipsilateral hemianalgesia of the face and contralateral hemianalgesia of the body

Lesions in upper medulla: destroy primary fibers in descending tract of V and secondary fibers in SL

Question 30

What is alternating trigeminal hemiplegia

Answer 30

Ipsilateral trigeminal anesthesia and paralysis, and contralateral spastic hemiplegia

Unilateral destruction of trigeminal n and corticospinal tract in pons

Question 31

What is trigeminal neuralgia?

Answer 31

epileptic-like discharges fro subnucleus caudalis

Facial pain that follows distribution of affected division of trigeminal n