6 Trigeminal Pathways - M Flashcards
Where are the cell bodies of CN 5 afferents primary located?
trigeminal/semilunar ganglion
What are the 4 major nuclei of the trigeminal tract?
- main/primary sensory nucleus (msT)
- trigmeninal motor nucleus (mT)
- spinal nucleus
- mesencephalic nucleus (mes)
Where is the main sensory nucleus (msT) found?
in the mid pons enlargement lateral to trigeminal motor nucleus (mT)
Which trigeminal nucleus extends rostrally?
Mesencephalic nucleus (mes)
Which trigeminal nucleus extends caudally into the cervical region?
Spinal nucleus
What afferents modalities are transmitted to the cortex via the primary sensory nucleus (msT)
discriminative tactile & proprioceptive senstations
What afferent modalities are transmitted via the spinal nucleus?
pain & temperature
What afferent modalities are transmitted via the mesencephalic nucleus (mes)?
proprioceptive afferents from the muscles of the mastication & the TMJ
Identify the following structures
- mesencephalonic nucleus
- main sensory nucleus
- trigeminal ganglion
- spinal (trigeminal) nucleus
What is the primary sensory afferent of the head and face?
Trigeminal nerve (V1, V2, V3); review distribution
What are the 2 divisions of the main sensory nucleus (msT)?
dorsomedial & ventrolateral divisions
What afferents are associated with the dorsomedial division of the msT
afferents from oral cavity
What afferents are assoicated with the ventrolateral division of the main sensory nucleus?
V1-V3
2nd order afferents of the msT nucleus project to what nucleus in the thalamus?
VPM
2nd order afferents from the ventrolateral division of the msT project to ____ VPM via what tract?
Contralateral VPM via the anterior trigeminothalamic tract
2nd order neurons from the dorsolateral division of the msT project to ___ VPM via what tract?
ipsilateral VPM via the posterior trigeminothalamic tract/ dorsal central trigeminal tract
fibers of the ventrolateral msT are joined by fibers from what other nuclei in the VPM?
spinal trigeminal nucleus to form the trigeminothalamic lemniscus
Through what brainstem structure does the dorsal central trigeminal tract ascend through?
The periaqueductal gray matter (surrounds cerebral aqueduct in the midbrain)
Where are tertiary neurons of the trigeminal pathway located?
cell bodies in the VPM and project to the primary somatosensory cortex
Tertiary neurons of the VPM project via what structure to reach the post-central gyrus?
The posterior limb of the internal capsule
What part of the head receives sensory innervation from the trigeminal nerve?
The anterior half
trigeminal afferents carrying pain & temp info enter ___ nucleus and then DESCEND via what tract?
enter spinal nucleus and DESCEND via spinal trigeminal tract before ascending via anterior trigeminothalamic tract
What are the 3 regions of the spinal nucleus?
- Pars/subnucleus CAUDALIS
- pars/subnucleus oralis
- pars/subnucleus interpolaris
4.
How are the afferent TO the ventrolateral msT organized?
V1 =posterior, V2 = middle, V3 = anterior/ventral
how are the afferents in the ventrolateral msT organized
V1 = anterior, V2 = middle, V3 = posterior
What is the obex?
narrowing of the 4th ventricle as it becomes the central canal of the spinal cord
How are V1-V3 organized in the pars caudalis?
V1= most rostral, V2 = middle, V3 = most posterior
The most rostral portions of the pars caudalis are located near what structure?
The obex in the medulla
The most caudal portions of the pars caudalis are located where?
in the upper cervical cord (C1-C3 area)
Does damage to the pars caudalis presents with a characteristic or non-characteristic pattern of nociceptive and thermal sensory loss?
Characteristic d/t little other lap between V1-V3
Damage to the caudal portion of the subnucleus caudalis results in loss of nociceptive and thermal sensory innervation where?
upper portions of neck and v3-C2 dermatomes
Damage to rostral portion of subnucleus caudalis results in nociceptive and thermal sensory loss where?
around mouth and nearby structures
2nd order neurons from the spinal nucleus decussate where and join what ascending tract?
At the level the 1st order neurons descended to in spinal nucleus; join the anterior trigeminothalamic tract to the contralateral VPM
Where is the pars oralis found?
the entrance of CN 5 in the pons –> upper medulla
What info goes to the pars oralis?
tactile info from the central region of the face
What are the boundaries of the subnucleus interpolaris?
upper medulla to the level of the obex (end of 4 ventricle in medulla)
What info does the pars interpolaris get?
sensory info from peripheral region of face
The pars oralis & interpolaris are heavily involved in what type of functions
somatic functions similar to that of the spinal cord
What structure do afferents from the subnucleus oralis and interpolaris pass through to enter the cerebellum?
inferior cerebellar peduncles
What sensory information does the mesencephalic nucleus (mes) convey?
unconscious proprioception & pressure from muscles of oral region
afferents from the mes nucleus travel to what structures?
msT, spinal nucleus & trigeminal motor nucleus (mT)
The mes nucleus sends afferents to what nucleus to form the jaw-jerk reflex?
The trigeminal motor (mT) nucleus
The trigeminal motor (mT) nucleus send motor fibers to PA 1 via what branch of CN5
V3/mandibular division
Where is the trigeminal motor nucleus found?
in the midpons medial to the msT nucleus
Damage to what type of nerves would result in an increase in reflexive strength?
UMNs
What muscle is involved in the jaw-jerk reflex?
masseter m
afferents from which nucleus innervated the muscle spindle of the masseter m.?
mes nucleus
afferent fibers of the corneal reflex terminate in what nucleus?
The spinal trigeminal nucleus (par caudalis)
2nd order neurons from __ nucleus travel via __ tracts to synapse on efferents in the facial (CN7) motor nucleus
spinal trigeminal nucleus; trigeminothalamic tracts
What are the 2 major trigeminocerebellar pathways
- Mesencephalic (mes) nucleus via pars interpolaris –> cerebellum
- Main sensory nucleus (msT) –> cerebellum
Proprioceptive input from the jaw regarding chewing/placement travels through which nucleus befor entering the cerebellum?
Mesencephalic nucleus –> pars interpolaris –> cerebellum
TMJ proprioception info enters cerebellum via what structure?
inferior cerebellar peduncle; (afferents from mes nucleus –> par interpolaris)
Where in the cerebellum does the main sensory nucleus project to?
anterior vermis via the superior cerebellar peduncle
What alters jaw placement/force during mastication?
food texture & consistency
A unilateral lesion of the trigeminal nerve results in what?
- Ipsilateral loss of sensation on anterior 1/2 of the head and motor innervation of the muscles of mastication
- Loss of jaw-jerk & corneal blink reflexes
Damage to what structure(s) causes alternating analgesia
damage to upper medulla may = damage to spinal trigeminal tract & spinal lemniscus
How does alternating analgesia present?
hemianalgesia of face ipsilateral to lesion & hemianalgesia of contralateral body
What causes alternating trigeminal hemiplegia?
unilateral lesion of the trigeminal nerve & corticospinal tract in the pons
How does alternating trigeminal hemiplegia present?
- ipsilateral trigeminal anesthesia and paralysis
- contralateral spastic hemiplegia
What is hemiplegia?
paralysis of 1 side of the body
What artery supplies the anterolateral tract & spinal trigeminal nucleus/tract?
Posterior inferior cerebellar a. <– vertebral a.
lesions or occlusions of PICA cause what syndrome?
lateral medullary (Wallenberg) syndrome
What are the signs of lateral medullary (Wallenberg) syndrome?
- contralateral hemianalgesia & hemithermoanesthesia on body
- ipsilateral hemianalgesia & hemithermoanesthesia on face
How would a lesion of the R trigeminal motor nucleus (mT) or trigeminal root present?
protrusion of the jaw to R (side of lesion)
