Trigeminal Pathways Flashcards
Primary afferents (1st order neuron) of the trigeminal N extend from the cell bodies in the _____.
It attaches to the brainstem as two adjacent roots (large sensory and smaller motor) on the ____.
Trigeminal ganglion
Ventrolateral aspect of the pons
Three sensory nuclei and one motor nucleus form a continuous cell column that extends from the _____ junction to rostral levels of the _____.
What are the four trigeminal nuclei?
Spinomedullary junction; mesencephalon/midbrain
Main sensory nucleus: forms an enlargement in the midpons slightly lateral motor nucleus
Trigeminal motor nucleus
Spinal nucleus: extends caudally form this level
Mesencephalic nucleus: extends rostrally all the way to the midbrain
The trigeminal nuclei have segregated distribution of afferent fibers depending upon modalities.
What do they convey?
Main sensory nucleus: fibers conveying touch and pressure terminate here
Spinal nucleus: fibers carrying pain and temp info terminate here
Mesencephalic nucleus: proprioceptive afferent from muscles of mastication and the TMJ
The main sensory nucleus is concerned with ____ and _____.
What are its two divisions?
Afferent somatotopic representation is inverted in the nucleus. Where are the three branches?
Discriminative tactile and proprioceptive sensations
Dorsomedial division: afferent input from oral cavity
Ventrolateral division: afferents from V1, V2, V3
V1: anterior
V2: in between
V3: posterior
The main sensory nucleus relays discriminative tactile info from the head to the ____ of the thalamus.
The ventrolateral division projects to the contralateral VPM via the _____. This will be joined by fibers from the spinal nucleus of V.
Ventral posteromedial nucleus (VPM)
Trigeminal leminiscus (anterior trigeminothalmic tract)
Dorsomedial division projects to the ipsilateral VPM via the ______. This ascends laterally to periaqueductal gray.
It terminates somatotopically within the VPM. The oral cavity is represented medially, external face laterally.
The tertiary axons from the VPM project via the _____ of the internal capsule to the ____.
Posterior dorsal trigeminothalmic tract (dorsal central trigeminal tract)
Posterior limb; primary somatosensory cortex
Anterior trigeminothalmic tract contains the ____.
Posterior trigeminothalmic tract contains the ___.
Trigeminal lemniscus
Dorsal central trigeminal tract
Spinal trigeminal nucleus receives info about ____ from the anterior half of the head.
Primary afferent fibers reach nucleus by turning caudally as they enter the pons to join the ____ and are positioned lateral to the nucleus.
Pain and temp
Spinal trigeminal tract
The spinal trigeminal nucleus has three regions?
Pars/subnuclues caudalis: most caudal part extending from the spinal cord to the obex
Pars/subnucleus oralis: most rostral part, extending from the main sensory nucleus to pontomedullary junction
Pars/subnucleus interpolaris: located in between in rostral medulla
Both the spinal trigeminal nucleus and tract extend caudally to about the _____.
They descend in the _____, a fiber tract lying immediately superficial to the nucleus.
The tract becomes continuous with ___ in the upper cervical cord.
3rd cervical segment
Spinal trigeminal tract
Lissauer’s tract
The different parts of the ipsilateral half of the face are represented in the _____ and ___.
____ fibers are most posterior.
____ are most anterior.
____ are in between.
Caudal spinal trigeminal tract and nucleus
Mandibular division; ophthalmic division; maxillary division
Each trigeminal division has a somatotopic arrangement with a rostral-caudal distribution. Fibers representing areas near the center of the face end near the ___.
Fibers representing areas toward the back of the head end in the ____.
Obex
Upper cervical cord
Arrangement of the pars/subnuclues caudalis allows for a smooth transition of ____ with _____.
Spinal levels processing cutaneous info originating at the back of the head
Brainstem levels processing similar cutaneous info from face
Trigeminal fibers ending in the cervical cord overlap ____ that represent adjacent areas of the skin.
Damage to the spinal trigeminal tract causes a pattern of sensory loss called ____.
The more caudal lesion causes ____. The more rostral lesion causes ____.
Spinal fibers
Onion-skin distribution
A larger area surrounding the mouth to be spared from sensory loss
Sensory loss that starts at the back of the head and converges on the mouth
In the pars/subnucleus caudalis pathway, second order axons from the caudal nucleus decussate and ascend in the ____.
It terminates in the ____ of the thalamus.
The tertiary axons extend in the posterior limb of the ____ to the primary somatosensory cortex.
Anterior trigeminothalmic tract (trigeminal lemniscus)
Contralateral VPM
Internal capsule
____ extends from the level of the entrance of V to the upper medulla. They receive _____ info from the central region of the face.
____ extends from the upper medulla to the level of the obex. It receives info from the peripheral region of the face.
They are involved in fx homologous to somatic fx of the spinal cord. They project fibers to the ____ through the _____ and carry tactile info projected to the _____.
Pars/subnucleus oralis; tactile info
Pars/subnucleus interpolaris
Cerebellum; inferior cerebellar peduncle
Contralateral VPM
The _____ is comprised of pseudounipolar neurons. It is the only nucleus in the CNS and can be considered as displaced trigeminal ganglion cells.
It conveys unconscious proprioceptive and pressure info from ____.
Mesencephalic nucleus
Muscles of the oral region
The mesencephalic nucleus projects to the _____. This allows _____ via the anterior/posterior trigeminothalmic tract.
Some axons terminate in the ____ to form the circuit for the ____ reflex.
Main sensory nucleus; conscious awareness of facial and oral proprioception
Trigeminal motor nucleus; jaw-jerk reflex
____ innervates the muscles of the PA 1 such as the muscles of mastication, tensor tympani, tensor palatini, mylohyoid, anterior belly of digastric.
The nucleus is located in the ____; the fibers emerge as a separate motor root and are distributed peripherally with the ____.
Trigeminal motor nucleus
Midpons; mandibular division
What are the two reflexes done by the trigeminal N?
Jaw-jerk
Corneal
The afferent limb of the corneal reflex originates from _____ in the cornea.
Their fibers travel on the V1 with their cell bodies in the _____. They terminate in the ipsilateral ____.
Trigeminothalamic fibers send collaterals bilaterally into the ____.
Pain/touch receptors
Trigeminal ganglion; spinal trigeminal nucleus
Facial motor nucleus (efferent limb of the reflex)
The jaw-jerk reflex is done by the afferent limb of the ____. Its peripheral process innervates the ____ and its central process synapses on a ____.
Mesencephalic trigeminal neuron
Masseter m spindle
Trigeminal motor neuron
The mesencephalic nucleus via the spinal nucleus (pars interpolaris) gives what info via what?
The main sensory nucleus moderates what via what?
Both process what info?
Proprioceptive input from the jaw related to chewing/jaw placement; via the inferior cerebellar peduncle (restiform body)
The amount of secondary neurons that project to the anterior vermis of the cerebellum; superior cerebellar peduncle
Info regarding jaw placement during mastication; food texture and consistency are altered as it is chewed, changing the demands on jaw muscles
What does a unilateral lesion in the trigeminal N cause?
Anesthesia and loss of general sensations in the trigeminal dermatomes
Loss of jaw-jerk reflex
Atrophy of muscles of mastication
Loss of ipsilateral and consensual corneal reflex
What is alternating analgesia?
What are the effects in pts?
Brainstem lesions in the upper medullary may destroy primary fibers in the spinal trigeminal tract and secondary fibers in the spinal lemniscus
Pt have ipsilateral hemianalgesia of the face and contralateral hemianalgesia of the body
What is alternating trigeminal hemiplegia?
Unilateral destruction of the trigeminal N and corticospinal tract in the pons
Ipsilateral trigeminal anesthesia and paralysis and contralateral spastic hemiplegia
Lateral medullary (Wallenberg) syndrome is caused by the _____ that supplies the anterolateral system and the spinal trigeminal nucleus/tract.
A vascular lesion of this vessel causes what?
Posterior inferior cerebellar A
Contralateral loss of pain (hemianalgesia) and temp (hemithermoanesthesia) over the body with ipsilateral loss of these modalities over the face
Tic douloureux (trigeminal neuralgia) produces ____ symptoms. Where?
What causes this?
Severe, episodic (paroxysmal) pain; “trigger zones”= the peripheral division of the maxillary or mandibular division ipsilaterally
Vascular compression of the trigeminal N root/ presence of microneuromas
