Trigeminal System

Question 1

Sensory origin of trigeminal

Answer 1

. Trigeminal ganglion
. Central fibers project to spinal trigeminal nucleus and tract, chief sensory nucleus, and mesencephalic nucleus and tract

Question 2

Trigeminal function

Answer 2

. Transmission of general somatic sensibility (vibration, touch, proprioception, pain, and temp.) of the greater part of head
. Motor innervation to mm. Of mastication

Question 3

General somatic afferent component

Answer 3

. General sensations of face, oral and nasal cavities, dura matter, and proprioception for assoc. mm.
. Functions like dorsal columns, ALS, and spinocerebellar tracts for rest of body

Question 4

Nuclei assoc. w/ GSA activity

Answer 4

. Spinal trigeminal nucleus and spinal trigeminal tract
. Chief (main/principal) sensory nucleus
. Mesencephalic nucleus

Question 5

Spinal trigeminal nucleus and tract

Answer 5

. Located in lat. tegmentum of medulla and caudal pons
. Nucleus is Rostral continuation of substantia gelatinosa of dorsal horn
. Tract is rostral continuation of Lissauer’s tract
. Carries pain and temp and crude touch info from head (analogous to ALS)

Question 6

Chief sensory nucleus

Answer 6

. Located in dorsolat. Pontine tegmentum and midpontine level, lat. to fibers of trigeminal n.
. Concerned w/ fine touch, 2-point discrimination, vibratory and conscious proprioception info from head
. Analogous to DCML

Question 7

Mesencephalic nucleus

Answer 7

. Located in rostral pons and caudal midbrain adjacent to PAG
. Represents primary sensory ganglia (like DRGs) that have become incorporated into CNS during brainstem development
. Concerned w/ unconscious proprioception info from head
. Analogous to spinocerebellar system

Question 8

Special visceral efferent component of trigeminal

Answer 8

. Motor innervation to mm. Of mastication and derivatives of branchial arch 1
. Motor nucleus: located in dorsolat. Pontine tegmentum at mid-pontine level, med. to fibers of trigeminal n. And chief sensory nucleus
. Fibers exit brainstem by passing through middle cerebellar peduncle alongside incoming sensory fibers of trigeminal n.
. Only travel to V3
. Receives bilateral cortical inputs

Question 9

T/F trigeminal n. Has non-overlapping dermatomes

Answer 9

T

Question 10

Trigeminal ganglion location

Answer 10

. Located in trigeminal (Meckel’s) cave in middle cranial fossa
. Contains neuronal cell bodies of sensory neurons of trigeminal n.

Question 11

Sensory component of trigeminal pathway

Answer 11

. Enters brainstem at mid-pontine level and passes through middle cerebellar peduncle
. Primary afferent axons enter chief nucleus or descend along lat. margin of brainstem to enter spinal trigeminal nucleus

Question 12

Somatotopy in spinal trigeminal nucleus

Answer 12

. Sensory inputs from lat. part of face (ear) project caudally in Sp V Nuc.
. Sensory inputs from middle part of face (cheek/eye) project in middle portion
. Sensory inputs from central part of face (mouth) project rostrally

Question 13

Ventral trigeminothalamic tract (VTTT)

Answer 13

. Fibers originate in spinal trigeminal and chief sensory nuclei
. Fibers originating from spinal trigeminal nucleus
. Fibers originating from chief sensory nucleus

Question 14

Dorsal trigeminothalamic tract (DTTT)

Answer 14

. Relatively small pathway
. Completely ipsilateral pathway only from chief sensory nucleus to VPM
. Clinical significance unknown

Question 15

Pathway of fibers originating from spinal trigeminal nucleus

Answer 15

. Fibers exit nucleus, decussate, and ascend up brainstem as part of VTTT
. Fibers that Carry pain and temp. Info ascend to contralateral VPM nucleus in thalamus (close to ALS)
. Somatotopically arranged to lat. aspects of primary sensory cortex in postcentral gyrus
. Gives off collateral branches to RF and tectum for reflexes for slow, dull pain and reflexes

Question 16

Pathway for fibers originating from chief sensory nucleus

Answer 16

. Fibers exit, decussate, and ascend to VPM nucleus of thalamus
. close to med. lemniscus
. VPM neurons will project somatotopically to lat. aspects of primary sensory cortex in postcentral gyrus