Lecture 08 Trigeminal Pathways Flashcards
Describe the course of the precise discriminative tactile information in trigeminal fibers of the face
A few incoming fibers will ascend only in the short ascending root of V and terminate in the main sensory nucleus of V
Describe the course of the proprioceptive information in trigeminal fibers
Some of the fibers adjacent to the ascending root course in the mesencephalic tract of V
Coveys the infor to the main sensory nucleus
Describe the course of the trigeminal fibers that convey pain (A delta and C) and temperature information from the face
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
What nucleus of the V is at the level of the trigeminal nerve?
Main sensory nucleus
What information does the Main sensory nucleus of V receive?
precise tactile, crude tactile and proprioceptive information from the face
What information from the face terminates in the descending nucleus of V?
All pain and temperature sensations as well as general tactile information from the face
What are the three subnuclei of the Descending Nucleus of V?
Subnucleus rostralis
Subnucleus interpolaris
Subnucleus caudalis
What information does the Subnucleus Rostralis receive?
Tactile information from the central region of the face
What information does the Subnucleus Interpolaris receive?
information from the peripheral region of the face
What information does the Subnucleus Caudalis receive?
Pain and temperature information from the anterior 1/2 of the head
What is the only nucleus in the CNS that is comprised of pseudo-unipolar neurons?
Mesencephalic Nucleus of V
What does the Mesencephalic Nucleus of V convey?
unconscious proprioceptive and pressure information from mm of the head and oral region
What does the Trigeminal Motor Nucleus innervate?
muscles derived from mesenchymal cell in the first branchial arch
Located at the same lvl of the brainstem as the main sensory nucleus
What is the course of the secondary axons from the subnucleus caudalis?
Decussate and ascend in the trigeminal lemniscus
TL terminates in the ventral posterior medial (VPM) nucleus of the dorsal thalamus
What do the tertiary axons from the VPM nucleus travel to?
the primary somesthetic cortex
Describe the Trigemino-reticulo-thalamic Pathway
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
What does the trigeminal input into the RF facilitate?
the ascending reticular activating system (ARAS), plays an important role in arousal and alertness
What is the fast pain pathway from trigeminal n fibers?
Descending tract of V->Subnucleus caudalis->TL->VPM->1* somesthetic cortex
What is another for trigeminal lemniscus?
anterior trigeminothalamic tract
What is the crude tactile pathways from the face?
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
Describe the precise tactile pathway from the face
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
What is the trigeminal lemniscus adjacent to as it ascendts?
medial lemniscus in the brainstem
Describe the proprioceptive pathways from the face
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)
Describe the Jaw-Jerk reflex
Rapid depression of chin
massteric n->mesencephalic nucleus->motor nucleus of V->massteric n->motor end-plate->clenching teeth
What trigeminal nuclei are the only ones that project to the cerebellum?
Subnuclei rostralis and interpolaris
What information via the trigeminocerebellar fibers through the ipsilateral inferior cerebellar peduncle is conveyed to the anterior vermis?
crude tactile (light touch) from the head
What information from the main sensory nucleus via superior cerebellar peduncle is conveyed to the anterior vermis?
precise tactile and proprioceptive info from the head
What does unilateral lesion of the trigeminal nerve result in?
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
What is alternating analgesia?
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
What is alternating trigeminal hemiplegia
Ipsilateral trigeminal anesthesia and paralysis, and contralateral spastic hemiplegia
Unilateral destruction of trigeminal n and corticospinal tract in pons
What is trigeminal neuralgia?
epileptic-like discharges fro subnucleus caudalis
Facial pain that follows distribution of affected division of trigeminal n
