Forbes: Cranial Nerve Nuclei

Spinal Nerves: General sensation from body wall or somatic structures.
Cranial Nerves: General sensation from head, mouth, teeth

S: Sensation from Viscera
C: Sensation from baroreceptors, pharynx, thoracia, abdominal viscera

S: Innervation of skeletal muscle
C: Inn of eye muscles and tongue

S: Sympathetics & Parasympathetics
C: Parasympathetics

C: Taste and Olfaction

C: Vision, Audition, Vestibular Function

C: Innervation of muscles derived from branchial arches

Separates LMN (GSE, SVE, GVE) and 2o Sensory (SVA, GSA, SSA).
Each nuclei = uninterrupted column of CNN (goes along entire brain stem)

Visceral = medial (to SL)
Somatic = lateral

X = Vagus.
W/spinal V nuc, dors mtr nuc of X, nuc. ambiguus & solitary nuc

solitary nucleus is associated with both GVA and SVA

Nuc. Ambiguus & dors motor nuc. of X contribute GVE fibers to cranial nerve X

Nuc ambiguus contributes to both IX and X

GSA: V (VII, IX, X)
SSA: (II), VIII
SVA: (I), VII, IX, (X)
GVA: IX, X
* Note: neurons from these nuclei get input from 1o afferents in the sensory cranial nerves (except for mesencephalic V)

GSE: III, IV, VI, XII
SVE: V, VII, IX,X, XI - assoc with branchial arches
GVE: III, VII, IX, X
* Note: Axons of the LMNs in these nuclei exit the CNS in motor cranial nerves.

Trigeminal nucleus

They are located in specific cranial nerve nuclei and travel in specific cranial nerves: Edinger-Westphal nucleus & oculomotor nerve; superior salivatory nucleus & facial nerve; inferior salivatory nucleus & glossopharyngeal nerve; dorsal motor nucleus of the vagus + nucleus ambiguus & the vagus nerve.

Superior cervical ganglion
(There aren't any sym neurons in the brain stem)

III, IV, VI

Travel through cavernous sinus and enter orbit via the superior orbital fissure

Nucleus of Edinger-Westphal --> Ciliary Ganglion --> Ciliary muscle / Pupillary constrictors
(1st = via CN III & preganglionic axon)
(2nd = via short ciliary nerves, postganglionic axon)

GVE (paraS) component of CN III.

Lateral (external strabismus
Diplopia
Ptosis
(above 3 are GSE)
Fixed & dilated pupil (GVE)
* 1st Sx = slowness of pupil light reflex

Ipsi to nerve.
If nucleus is involved; bilateral

Eye cannot move down & in
Diplopia when looking down
Problems descending stairs & reading

Contralateral to nucleus;
Ipsilateral to nerve after it decussates

Medial or internal strabismus
Diplopia

Ipsilateral to nerve & nucleus
If lesion involves the nucleus + the surrounding part of the reticular formation (PPRF) >> paralysis of lateral gaze

Unilateral UMN lesions produce no noticeable deficits involving the eye muscles BECAUSE
Oculomotor, Trochlear & Abducens nuclei receive bilateral corticobulbar input -- indirectly via centers in the brain stem.
Note: Bilateral Corticobulbar input means that both the left and right cerebral cortex send input to both the right and left cranial nerve nuclei such as III, IV and VI.

coordinates activities of the eye muscles via connections with the eye muscle nuclei (III, IV, VI) and the vestibular nuclei (VIII).

Afferent limb of reflex: Vestibular Nerve
Efferent limb of the reflex: Oculomotor, Trochlear and Abducens Nerves

coordinates movement of the eyes to fix an image on corresponding points of the retina of each eye -- in response to vestibular stimulation

From vestibular apparatus

1. Vestibular or Scarpa's ganglion
2. Vestibular nucleus

Cerebellum (vestibulocerebellar tract; via inferior crebellar peduncle; terminate in flocculonodular lobe)
LMNs in SC/BS: Vestibulospinal tr.
Medial Longitudinal Fasciculus (MLF)

Dizziness, ataxia, abnormal eye movements, nausea, vomiting

Lack of coordination of eye movements (internuclear ophthalmoplegia)

In the vestibular nuclei.

in the internal auditory meatus.

Is d/t damage to MLF.
--> lack of coordination of eye mov't (especially in medial-lateral direction)
May be 1st Sx of MS

Look to side opposite to lesion
Ipsi eye: cannot move beyond midline (3rd nucleus and MR aren't connected via MLF)
Contra eye: okay (connections from vest nuclei and PPRF --> MLF --> VI and the LR are fine)

Center for lateral gaze (PPRF)
Center for Vertical Gaze

Frontal Eye Fields
Occipital Eye Fields

Paramedian Pontine Reticular Formation (PPRF) or Center for Horizontal Gaze

In pontine RF near the abducens nucleus

Coordinated movements of medial and lateral rectus muscles via input to III, VI

Higher cortical centers (i.e. frontal eye field)

Paralysis of lateral gaze to side of lesion.

Test: Look to the side of lesion
Eye ipsilateral to lesion: Cannot abduct to look at the target because lateral rectus innervation by VI is destroyed.
Eye contralateral to lesion: Cannot move past midline because input to IIIrd nucleus & medial rectus from PPRF & VIth nucleus is destroyed.

In the periaqueductal gray matter of midbrain

Superior rectus (III)
Inferior rectus (III)
Inferior oblique (III)
Superior oblique (IV)

By pressure from a pineal tumor

Frontal and Occipital Eye Fields

Area 8 (caudal part of middle frontal gyrus)

Voluntary, conjugate movements (are independent of visual stimuli)

To lateral and vertical gaze centers

Stimulation: eyes turn to the opposite side (ex. seizure)
Destruction: eyes "look at the lesion" (ex. stroke)

Visual Association Cortex
They project to tectum

Fixation of gaze, automatic scanning eye movements, i.e. involuntary or reflex tracking of an object or smooth pursuit tracking movements
Accommodation-convergence rx
Recognition of what is seen
Stereoscopic features of vision
Color vision

Visual agnosia (do not recognize what you see)
Disruption of reflexes such as fixation and accommodation-convergence.

Carries somatic sensory info from the head
Discriminative Touch & Proprioception from the HEAD is carried by the part of the Trigeminothalamic tract that receives input from large diameter primary afferents in the trigeminal nerve.
Pain and Temperature from the HEAD is carried by the part of the Trigeminothalamic tract that receives input from small diameter primary afferents in the trigeminal nerve - -and to a small extent in cranial nerves VII, IX, & X.

x

x

First-order neurons are inside CNS

Proprioception from muscle spindles in muscles of mastication, etc
Afferent limb of the jaw jerk reflex.

Recti (medial, inferior, superior)
Inferior oblique
Levator paplebrae superioris

Superior Oblique (SO4)

Lateral Rectus (LR4)

Oculomotor (complex of) nuclei (below aqueduct at level of sup colliculus in midbrain)

Trochlear nuclei (below aqueduct at inferior colliculus in midbrain)

Abducens nuclei (in floor of 4th ventricle at level of pons, below facial colliculus (which is formed by abducens nucleus + facial motor nerve fibers))

After nucleus: travel ventral thru midbrain.
Exit: ventral aspect of brain stem (in interpeduncular fossa)
Travels btw posterior cerebral and superior cerebellar arteries --> cavernous sinus --> superior orbital fissure --> orbit.

Leaves nucleus, goes dorsally around aqueduct.
Decussation: in superior medullary velum
Exit: dorsal aspect of BS (caudal to inferior colliculus)
Travels around midbrain --> btw posterior cerebral and superior cerebellar arteries --> cavernous sinuse --> sup orbital fissue --> orbit

Leave nucleus, travel ventrally thru pons.
Exits on ventral aspect of pons at P/M junction.
Nerve travels rostrally from post fossa --> cavernous sinus --> SOF --> orbit

Oculomotor: ipsilateral
Trochlear: contralateral (decussates)
Abducens: ipsilateral

Info about gravity, rotation, acceleration.
Maintains posture/equilibrium; coordinates head and eye movements

At the pons/medulla junctions (CP angle) as root separate from cochlear nerve

1. Vestibular (Scarpa's) ganglion (in internal auditory meatus)
2. Vestibular nuclei (in upper medulla / lower pons in vestibular trigone (floor of 4th ventricle)

P: receptors (hair cells) in static/kinetic portions of labyrinth
C: Form vestibular nerve, synapse in vestibular nuclei and cerebellum.

Cerebellum (travel in ICP) - omp in coordinating muscle activity necessary for balance/proper eye position.
LMNs in SC and BS (VST and MLF)

Facilitates antigravity muscles (extensors) important in maintaining posture

D: --> cervical segments (coordinates head/neck mov't)
A --> nuclei of II, IV, VI (coordinates conjugat mov't of eyes and visual tracking as head moves)

Reticular formation (influences ANS function (RST) and levels of consciousness (ARAF))
Thalamus (insignificant)

Dizziness, falling, abnormal eye movements, N/V

Acoustic neuroma in cerebellopontine angle

Relays auditory input

1. Cochlear (spiral) ganglion (in axis of cochlea and around modiolus.
2. Dorsal & ventral cochlear nuclei (located near vestibular nuclei at the MP junction, dorsolateral (dorsal nucleus) and ventrolateral (ventral nucleus) to the inferior cerebellar peduncle).

Receptors (hair cells) of the cochlea.

See page 11 / Slide 30,31

Projection to cerebral cortex is primarily contralateral, but there is a significant ipsilateral component.

Frequency distribution along basilar membrane of the cochlea (high --> low frequencies)

Auditory pathway

Ipsilateral deafness
(ex. acoustic neuroma)

Above the cochlear nuclei

If Wernicke's association cortex in dominant hemisphere is involved.

Because it is the only location where primary afferent cell bodies are located within the CNS (deal with proprioception from muscles of mastication)

GSA, SVE

Carries input from touch, pain, temp, proprioception in the
1. skin of face/forehead
2. scalp back to vertex
3. oral and nasal mucosa (anterior tongue
4. sinuses
5. teeth
6. supratentorial dura

Ophthalmic
Maxillary
Mandibular

1. Trigeminal ganglion (except for those in mesencephalic trigeminal nucleus)
2. Main V nucleus; spinal V nucleus

Pons, at same level as V sensory root enters ventrolateral surface.
Lateral to trigeminal motor nucleus.

Fibers: larger diameter 1o fibers of CN V
Modality: discriminative touch and proprioception (analogous to DC (grac + cun) of DCML)

Extends from main V nucleus in pons down to SC (then blends with dorsal horn through C3).
1o fibers (prior to synapsing on 2o) travel DOWN lateral side of sVn and form tract of the sVn - which is coextensive with Lissauer's tract)

At al levels of the sVn.

pain, temperature, some tactile

STT
Spinal V nucleus approx. = Laminae I to V of spinal cord dorsal horn
Spinal V tract approx. = Lissauer's tract (dorsolateral fasciculus)

= projection of 2o V information from main and spinal Vn to the ventral posteromedial nucleus (VPM) of thalamus.

see page 13

TTT: don't form distinct bundle crossing over.
sVn: cross throughout rostral-caudal extent of sVn.
mVn: cross at level of mVn

Primary somesthetic cortex in somatotopic fashion (postcentral gyrus nearest the lateral fissue)

1. --> other CNN (motor) for reflexes
2. Reticular formation as input to ARAS

Mesencephalic V nucleus

In midbrain, thin band extends rostro-caudally in most lateral aspect of periaqueductal gray matter.
Synapse (with other large diameter afferents) in main sensory nucleus.

(Muscles derived from first branchial arch)
* Muscles of mastication (masseter, temporal, lat/med pyerygoids
* Tensor tympani
* Anterior bely of digastric
* Tensory veli palatini
* Mylohyoid

In the trigeminal motor nucleus
* located in pons (same leves as V motor root exits ventro-lateral surface).
* is medial to sensory mVn

With the mandibular division of the sensory nerve.

No decussation, thus ipsilateral.

Corticobulbar fibers terminate bilateraly - thus each mVn receives CBT input from both hemispheres.

Jaw jerk

Loss of touch, proprioception, pain, temp.
Anesthesia, paresthesia
Trigeminal neuralgia (aka tic douloureux)
* Laterality depends on location of lesion - whether above or below decussation of the TTT.
* Modalities affected depend on which nuclei are involved.

LMN: ipsi paralysis and atrophy of muscles of mastication
UMN: unilateral usually produces little deficit

GSA, SVA, SVE, GVE

General sensation from the skin of external ear, wall of auditory tube and outer surface of tympanic membrane.

Geniculate ganglion

The central processes of 1o neurons are located in the nervus intermedius.
These will enter the spinal trigeminal tract and synapse in the spinal V nucleus.
(Pathway to cortex is same as spinal V (via thalamus))

Taste from anterior 2/3 of tongue

Geniculate ganglion

1o neuron central processes in nervus intermedius. --> solitary tract or fasciculus / synapse in rostral solitary nucleus.
Send axons in the central tegmental tract, synapse in VPM-nucleus of thalamus (via reticular formation) and hypothalamus.

To Area 43 of cortex

Loss of taste in anterior 2/3 of tongue.
Minimal loss of general sensation from ear, auditory tube, outer surface of tympanic membrane.

(Muscles of 2nd arch)
Muscles of facial expression, posterior belly of digastric, buccinator, stapedius, platysma, stylohyoid

Facial motor nucleus

ugh...page 16 :)

No crossing - ipsilateral

Corneal or blink reflex

Corticobulbar input (UMN) is bilateral to facial neurons innervating upper face, but contralateral only to the neurons innervating lower face.

Aaron Swanson

contralateral lower face paralysis

Ipsilateral upper and lower face paralysis (called Bell's Palsy when lesion is at or beyond the stylomastoid foramen)

Deficit in VI and VII

Deficits in VII and VIII

Superior salivatory and lacrimal nuclei.

Facial GVE (ParaS)

General sensation from skin of external ear, internal surface of tympanic membrane, posterior 1/3 of tongue, upper pharynx.

1. sup/inf GP ganglia
2. Spinal V nucleus

Afferent limb of gag reflex

Taste from posterior 1/2 of tongue

1. Inferior (petrosal) GP ganglion
Central processes of 1o travel in solitary tract / fasciculus after entering brain stem - synapse in 2. rostal solitary nucleus (then project bilaterally to hypothalamus, thalamus, cortex as for taste input (facial)

Input from carotid sinus (baro) and carotid bodies (petrosal) ganglion

1. inferior GP (petrosal) ganglion
(travel in sol tract)
2. caudal solitary nucleus

1. Reticular formation and hypothalamus
2. involve reflex control of CV and resp function
3. Operate at "subconscious" level

VII, IX, X
SVA: Solitary / Gustatory nucleus (rostral part)

Stylopharyngeus (derived from 3rd arch)

Rostral nucleus ambiguus

Corticobulbar (UMN)

Hypothalamus, olfactory system, etc.

General sensation from skin of external ear, external auditory canal, external surface of TM, lower pharynx, larynx, and meninges of posterior cranial fossa.

1. superior (jugular) and inferior (nodose) vagal ganglia.
2. Spinal V nucleus (via spinal V tract)

Taste from epiglottis (little importance in adults)

1. inferior vagal ganglion (travel in sol tract)
2. rostral solitary nucleus (go to hypothal, thalamus, cortex as taste input over CN VII and IX

Input from aortic sinus, aortic bodies, pharynx, larynx, and thoracic/abdominal viscera

1. Inferior vagal ganglion
2. Caudal solitary nucleus

Reticular formation and hypothalamus
Reflex control of CV, resp, alimentary function
* no appreciable cortex projection here

(Muscles from 4th and 6th arches)
Striated muscles of larynx and pharynx (expect SP and LVP)
Palatoglossus (tongue)

Nucleus ambiguus

efferent limb of gag reflex

* Absent gag reflex
* Ipsi paralysis of palate, pharynx, larynx
* Deviation of uvula
* Droopy soft palate

Fatal

None (projections from cortex are bilateral)

Dorsal motor nucleus of vagus (located beneath vagal trigone in floor of 4th ventricle) and nucleus ambiguus

* Afferents from hypothalamus, olfactory system, solitary nuclei, reticular formation

SCM, trapezius

Spinal accessory nucleus (C1-C5)

Bilaterally on spinal acc nucleus (though contralateral dominates)

Downward/lateral rotation of scapula; some shoulder drop (D/t loss of traps); weakness in turning head to the side contralateral to lesion

Transient, contralateral paresis or paralysis in traps/SMC

Muscles of tongue (except palatoglossus - X)

Hypoglossal nucleus (located in floor of 4th ventricle beneauth HG trigone)

Btw medial lemniscus and pyramid (medially) and inferior olivary nucleus (laterally)

Ipsil weakness w/neurogenic atrophy; deviation of tongue to same side as lesion when protruded.

Contralateral weakness (tongue may deviate to opposite side when protruded)

Deviation is to the weak side, whether UMN or LMN lesion!