Brainstem and Cranial Nerves

8/19/2019 Brainstem and Cranial Nerves

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Neuroanatomy: Brainstem and Cranial Nerves

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BRAINSTEM and CRANIAL NERVES

Lecturer: Julius Ceazar H. Reyes MD

BRAINSTEM:

The lowermost part of the brain connecting the cerebrum and the spinal cord

Packed with nuclei and tracts

Anterior to cerebellum Transmitted by the Foramen Magnum

3 C’s of Brainstem: ! Conduit – bridges the tracts coming from cerebrum to the cerebellum and spinal cord and

vice versa ! Center – respiratory, cardiovascular and other vital centers are located in the brainstem ! Cranial Nerves – nuclei and nerve fibers of the last 10 cranial nerves (III-XII) arises from the

brainstem

Components: ! Midbrain ! Pons ! Medulla

Cerebellar Peduncles – structure that connects the brainstem to the cerebellar hemisphere ! Superior Cerebellar Peduncle / Restiform Body = connects the medulla to the cerebellum ! Middle Cerebellar Peduncle/ Brachium Pontis = connect the pons to the cerebellum ! Superior Cerebellar Peduncle / Brachium Conjunctivum = connects the midbrain to the

cerebellum




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White matter that will pass the brainstem must pass the cerebellar peduncle before it reaches thecerebellum

Ex. Spinocerebellar tract coming from the vestibular nucleus

EXTERNAL FEATURES

A. Medulla Oblongata Anterior:

Anterior Median Sulcus – continuous with the anterior median sulcus of the spinal cord,will separate brainstem in two halves

Pyramid – paired anterior swelling containing fibers of the Corticospinal Tract

Olive- anterolateral swelling formed by the Inferior Olivary Nucleus Posterior: (Lower Half or Closed Segment- with central canal in the cavity)

Posterior Median Fissure – continuous with the posterior median fissure of the spinalcord

Obex – marks the area of area postrema (rostral to obex) which is the center for

vomiting. The Area Postrema is one of the regions in the CNS devoid of the blood-brain-barrier.

Gracile Tubercle / Clava – midline swelling containing the gracile nucleus

Cuneate Tubercle –lateral to gracile tubercle containing the cuneate nucleus Posterior: (Upper Half or Open Segment)

Hypoglossal Trigone – marks the location of the hypoglossal nerve

Vagal Trigone – marks the location of the Dorsal Motor Nucleus of CN X




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B. Pons Anterior:

Pontine Protuberance – two anterior swelling that forms the Basis Ponti

Pontine Sulcus – midline depression that is occupied by the Basilar Artery Posterior

Posterior Median Fissure – continuous with the posterior median fissure of the medulla

Facial Colliculus – posterior swelling formed by the fibers of the facial nerve as it windsaround the nucleus of the abducent

Medial Eminence – Midline elevation above the facial colliculus

Vestibular Area – marks the location of the vestibular nucleus

Locus Ceruleus – pigmented area capable of producing Norepinephrine. Activated instress situations.

C. Midbrain Anterior:

Cerebral Peduncle / Crus Cerebri Posterior:

Corpora Quadrigemina / Tectum / Tectal Plates ! Superior Colliculus ! Inferior Colliculus




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INTERNAL FEATURES

Structures Found in Multiple Segments of the Brainstem 1. Trigeminal Nucleus

At all levels of the brainstem, the sensory nucleus of trigeminal nerve will beappreciated

2. Corticospinal Tract:

Crus Cerebri

Basis Ponti

Pyramids Note: corticospinal (cortex to spinal cord), corticobulbar (cortex to brainstem)

? Both will serve as upper motor neuron

? In the spinal cord, the lower motor neuron: anterior horn cell

? In the brain, lower motor neuron: cranial nerve with motor component Note: from origin of upper and lower extremity, fibers will descend to corona radiata, internal capsule, posterior limbof internal capsule, will pass cerebral peduncle, then anterior surface of pons, medulla oblongata, pyramids, at the

inferior medulla, this is the time when the fibers will cross its opposite side (90% will cross, 10% will remainuncross), they will descend as corticospinal tract, will synapse on the anterior horn cell. We have two types ofcorticospinal tract, the ventral or the anterior corticospinal tract, and lateral corticospinal.

3. Spinothalamic Tract




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The continuation of the Spinothalamic tract in the spinal cord passing the brainstembefore synapsing to the VPL of thalamus

Note: Primary sensory or primary tactile sensation will utilize 3 order neuron, first order is dorsal root ganglion. If

it is a spinothalamic tract, the second order neuron is substantia gelatinosa. They will ascend on thecontralateral side. They will all pass to the all components of brain stem then it will terminate on the thalamus atVPL before it will project at the cerebral cortex at area 312.

4. Trigeminothalamic Tract

Decussated fibers of the trigeminal nucleus as they ascend in the brainstem beforesynapsing to the VPM of the thalamus

5. Vestibulospinal Tract and Medial Longitudinal Fasciculus (MLF)




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Vestibulospinal tract = theses are fibers arising from the Vestibular nucleus. Itdescends in the spinal cord to synapse in lamina VII and VIII of the spinal cord

MLF = these are tracts of white matter containing fibers that connects with CNIII, IV andVI, superior and inferior colliculi, and vestibular nucleus. These f ibers are concerned withVestibulo-ocular and Optokinetic Reflexes

6. Medial Lemniscus

Crossed fibers arising from the cuneate and gracile nucleus carrying consciousproprioception. Fibers ascend in the brainstem and terminate in the VPL of the thalamus.(These are the continuation of the Dorsal Column Tracts of the spinal cord).

7. Lateral Lemniscus




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White tracts carrying auditory impulse coming from Cochlear Nucleus. It ascends in thebrainstem to synapse either in the Superior Olivary Nucleus, Inferior Colliculus and VPMof Thalamus

A. Medulla Oblongata

a. Level of Pyramidal DecussationNucleus:

Cuneate Nucleus! 2nd Order Neuron of the Dorsal Column carrying conscious

proprioception arising from the upper trunk (C1-T6) and upper limb

Gracile Nucleus ! 2nd Order Neuron of the Dorsal Column carrying conscious

proprioception arising from the lower trunk (T6 and below) and lower limb

Accessory Nucleus ! Motor Nucleus of the Accessory Nerve

Spinal Trigeminal Nucleus ! Spinal Trigeminal Nucleus emerges at this level. It is believed that the

nucleus is the continuation of Substantia Gelatinosa of the Spinal Cord. Tracts:

Decussation of Corticospinal Tract




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! The highlight of this level is the Decussation of the Corticospinal Tracts.90% of the fibers of CST crosses the midline in this level and theremaining 10% remain uncrossed

Spinothalamic Tract

Spinocerebellar Tract ! These are white matter tracts from the spinal cord carrying unconscious

proprioception impulse. These fibers will terminate in the cerebellarhemisphere. ! Ventral Spinocerebellar Tract – Ascend in the brainstem and will enter

the cerebellum via the Superior Cerebellar Peduncle. ! Dorsal Spinocerebellar Tract – Ascend in the brainstem and will enter the

cerebellum via the Inferior Cerebellar Peduncle.

Vestibulospinal Tract

Spinal Trigeminal and Trigeminothalamic Tract Cavity:

Central Canal b. Level of Great Sensory Decussation

Nucleus

Accessory Cuneate Nucleus

Hypoglossal Nucleus ! Motor Nucleus of CN XII

Tracts

Decussation of the Medial Lemniscus ! This is the highlight of this level where the fibers of the cuneate and

gracile tubercle crosses the midline and will ascend as the MedialLemniscus

Corticospinal Tract

Spinocerebellar Tract


Spinal Trigeminal and Trigeminothalamic Tract Cavity

Central Canal

Others: Area Postrema

! Vomiting Center ! Rostral to Obex

c. Level of Inferior Olivary NucleusNucleus:

Inferior Olivary Nucleus ! Gray folded nucleus (worm-like) opening medially known as the hilum

involved in control and coordination of movements, sensory processingand cognitive tasks likely by encoding the timing of sensory inputindependently of attention or awareness

! Inputs: Afferent Cerebral Cortex Basal Nuclei Midbrain via Red Nucleus Spinal Cord Medulla via Vestibular Nuclei Cerebellum

! Output - Efferent Cerebellum via inferior cerebellar peduncle

Nucleus Ambiguus ! A motor nucleus that controls the muscles of the pharynx. ! It is shared by Cranial nerve IX, X and XI

Nucleus Tractus Solitarius ! Rostral Nucleus

Involve in taste sensation of the tongue. Shared by Cranial nerve VII, IX and X

! Caudal Nucleus Involve in general visceral sensations Shared by Cranial nerve IX and X Neurons in this zone project to the nucleus ambiguus, dorsal

motor nucleus of vagus, and reticular formation in the medulla Concerned with Cardiovascular and Respiratory functions

Dorsal Motor Nucleus




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! The pre-ganglionic neuron of CN X carrying general visceral efferentfibers to the abdominal and thoracic viscera

Inferior Salivary Nucleus ! The pre-ganglionic neuron of CN IX carrying general efferent fibers to the

Parotid Gland Tracts

Medial Lemniscus Corticospinal Tract

Spinothalamic Tract



Fourth Ventricle Centers:

Respiratory Center

Sneezing Center

Swallowing Center

Yawning Center

B. Pons

2 major internal regions of the pons

! Basis Ponti Anterior Portion that forms the Pontine Tubercle

It contains:

Pontine Nuclei

Pontocerebellar Tracts that connects with the cerebellum at theBrachium Pontis

Motor Tracts: Corticospinal, Corticobulbar andCorticopontocerebellar Tracts

! Tegmentum

Area posterior to basis ponti

Contains white matter tracts coming from the midbrain and medulla Houses the nucleus of CN V, VI, VII, VIII

a. Level of Facial ColliculusNucleus:

Abducent Nucleus ! Motor Nucleus of CN VI

Facial Nucleus ! The Motor Nucleus of CN VII ! The highlight of this level is when the fibers of CN VII looping around the

abducent nucleus before exiting at the pontomedullary junction. Thisconfiguration creates a swelling in posterior pons known as the facialcolliculus.

Vestibular and Cochlear Nucleus ! The Nucleus of CN VIII ! Vestibulocochlear Nerve enters the brainstem at the pontomedullary

junction adjacent to CN VII. It carries auditory (sound) stimulus comingfrom the Organ of Corti and balance stimulus from the Semicircularcanals of the inner ear.

Spinal Trigeminal Nucleus

Pontine Nucleus




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Tracts:

Corticospinal Tract

Spinothalamic Tract

Pontocerebellar Tract

Lateral Lemniscus ! Ascending fibers of the Cochlear Nucleus (see description above)

! In the auditory pathway, some fibers will decussate and some fibers willascend on the ipsilateral side.

Trapezoid Body ! This will represent the decussation of the lateral Lemniscus.

Medial Longitudinal Fasciculus

Medial Lemniscus


Fourth Ventricle

b. Level of Main Sensory and Main Motor Nucleus of Trigeminal NerveNucleus:

Main Motor Nucleus of Trigeminal Nerve

! Motor Nucleus of CN V that controls the muscles of mastication Main Sensory Nucleus of Trigeminal Nerve

! Principal Sensory Nucleus of CN V that receives touch sensation

Superior Salivary Nucleus ! The pre-ganglionic neuron of CN VII carrying general efferent fibers to

the Submandibular and Sublingual Glands Tracts:

Corticospinal Tract

Spinothalamic Tract Pontocerebellar Tract

Lateral Lemniscus

Trapezoid Body


Medial Lemniscus Trigeminothalamic Tract

Cavity:

Fourth Ventricle

C. Midbrain

2 major internal regions of the midbrain

! Cerebral Peduncle

Crus Cerebri

Two masses of white matter containing the Corticobulbarand Corticospinal tracts

It is separated from the tegmentum by a mass ofpigmented body known as the Substantia Nigra

Substantia Nigra ! Large motor nucleus situated between the

tegmentum and crus cerebri

! Composed of medium-size multipolar neurons

! Zones: Substantia Nigra Pars Compacta

Contains pigmented neuronswhich expresses dopamine asthe neurotransmitter

Substantia Nigra Pars Reticulata




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Contains iron compounds whichexpresses GABA andCholinergic neurotransmitters

Tegmentum

Contains the periaqueductal gray matter, nucleus of CNIII and IV, ascending and descending white matter tracts

!

Tectum / Corpora Quadrigemina / Tectal Plates

Superior Colliculus

Inferior Colliculus

a. Level of Superior ColliculusNucleus:

Superior Colliculus ! Ocular Reflex ! Reflex Center for eye and head movements in response to visual stimuli

Substantia Nigra

Trochlear Nucleus ! Motor nucleus of CN IV. The fibers of trochlear nucleus decussate on the

posterior tegmentum before it emerges in the posterior midbrain just

inferior to the inferior colliculus.! It is then regarded as the only crossed cranial nerve and the longestcranial nerve intracranially.

Trigeminal Mesencephalic Nucleus ! The proprioceptive nucleus of CN V ! It is concerned with mechanisms that control the force of bite

Tracts:

Corticospinal Tract

Spinothalamic Tract

Lateral Lemniscus


Medial Lemniscus

Trigeminothalamic Tract

Cavity: Cerebral Aqueduct of Sylvius

b. Level of Inferior ColliculusNucleus

Inferior Colliculus ! Auditory Reflex ! Reflex Center for eye and head movements in response to sound stimuli

Substantia Nigra

Oculomotor Nucleus ! Main motor nucleus of CN III

Edinger-Westphal Nucleus ! Parasympathetic Nucleus of CN III ! Governs the pupillary light reaction

Red Nucleus ! Afferent Fibers (Input to Red Nucleus)

Cerebral Cortex (Corticorubral) Deep Cerebellar Nuclei (Cerebellorubral)

! Efferent Fibers (Output of the Red Nucleus) Spinal Cord (Rubrospinal Tract) Cerebellum Reticular Formation Inferior Olive

Tracts:

Corticospinal Tract

Spinothalamic Tract

Lateral Lemniscus

Medial Longitudinal Fasciculus Medial Lemniscus

Trigeminothalamic Tract Cavity:

Cerebral Aqueduct of Sylvius

CRANIAL NERVES




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12 pairs of nerve fibers that exits the CNS. Designated with Roman Numerals

Functional Components of Cranial Nerves ! Somatic Efferent Fibers (Motor)

Motor nerves innervating the Extraocular Muscles (III, IV, and VI) and theTongue (XII)

! Special Visceral Efferent Fibers (Motor)

Motor nerves innervating the Facial Muscles (VII), Muscles of Pharynx andLarynx (IX, X), Muscles of Mastication (V) and Neck Muscles (XI)

! Visceral Efferent Fibers (Motor) Preganglionic Parasympathetic Fibers Pupillary Constrictors (III), Salivary Glands (VII, IX), Heart, Lung and Bowel

Movements and Secretions (X) ! Visceral Afferent Fibers (Sensory)

Fibers carrying taste or gustatory sensation (VII, IX, X) Sensation from the GIT, Heart, Vessels and Lungs (IX, X)

! Somatic Afferent Fibers (Sensory) Fibers carrying sensation from the skin, mucus membrane and joint receptors of

the temporomandibular joint (V, VII, IX, X)

! Special Sensory Fibers (Sensory)

Smell sensation (I) Vision (II) Hearing and Balance (VIII)

Notes on Corticobulbar Tract: Motor Nucleus of Cranial Nerves receives its stimulation from the Corticobulbar tract. Connects the cortex and the motor neuron of the cranial nerves It originates from Area 4 where the face and oropharynx of motor homunculus is represented. Axons descend together with the Corticospinal tract at the Corona radiata and internal capsule. In the internal capsule, the CBT occupies the genu while the CST forms the posterior limb. CBT terminates in the brainstem to synapse with bilateral motor neurons of Cranial Nerves Exception: Contralateral Supply from CBT

! Ventral Motor Nucleus of CN VII ! Motor Nucleus of CN XII

A. OlfactoryWill be discussed in the Olfactory and Limbic System Lecture

B. OpticWill be discussed in Eye, Orbit and Visual Pathway




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C. Oculomotor Nucleus

! Main Oculomotor Nucleus Nucleus controlling the Extraocular muscles and Levator Palpebrae

Superioris, except the lateral rectus and superior oblique muscle ! Edinger-Westphal Nucleus

Parasympathetic Nucleus of CN III Governs the Pupillary Light Reflex Reaction

Shared by CN II (Sensory Arm) and CN III (Motor Arm)

Pathway: ! Light (Stimulus) ! Retina (Receptor) ! Optic Nerve, Optic Chiasm, Optic Tract (Afferent Arm) ! Pretectal Nucleus (Interneuron)

Nucleus connecting the sensory arm and themotor arm of the reflex

It synapses to bilateral Edinger WestphalNucleus

! Edinger Westphal Nucleus (Efferent Arm) Nucleus send fibers to the Ciliary Ganglion

! Pupillary Constrictors and Ciliary Muscle (Effector)

Nerve ! Arises at the anterior midbrain between the cerebral peduncles (Interpeduncular

Fossa) ! Nerve fibers traverses the red nucleus ! Enters the Orbit via the Superior Orbital Fissure ! Innervates the Extraocular Muscle except:

Lateral Rectus Superior Oblique

D. Trochlear Nucleus

! Motor Nucleus of CN IV

! Controls the Superior Oblique (SO4) Nerve

! The only crossed cranial nerve

! The only nerve that exits at the posterior midbrain at the level of inferior colliculus

! The longest cranial nerve intracranially. ! Enters the orbit via the Superior Orbital Fissure

E. Abducent Nucleus

! Motor Nucleus of CN VI ! Controls the Lateral Rectus

Nerve

! Exits the anterior brainstem at the pontomedullary junction

! Supplies the lateral rectus

! Enters the orbit at the Superior Orbital Fissure

F. Trigeminal Nerve

! 3 Divisions: Ophthalmic Division V1

Enters the intracranial cavity via Superior Orbital Fissure

Carrying sensation (pain, temp, light touch) stimulus fromanterior scalp, nose, anterior nasal cavity, lacrimal gland andeye.

Maxillary Division V2

Enters the intracranial cavity via Foramen Rotundum

Carrying general sensation from the lower eyelid, cheek, upperlip, maxillary sinus, maxillary teeth, hard and soft palate.

Mandibular Division V3

Enters the intracranial cavity via Foramen Ovale

Mixed nerve (both sensory and motor) ! Sensory:

Jaw, TMJ, Mandibular teeth, tongue

! Motor:




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Muscles of Mastication

Masseter, Temporalis, Pterygoids, TensorVeliPalatini, Mylohyoid, Anterior Belly ofDigastric and Tensor Tympani

! Sensory Fibers of V1, V2, V3 will synapse in Trigeminal Ganglion

! Trigeminal Ganglion First order neuron similar to dorsal root ganglion of the spinal cord

! Fibers of the Trigeminal Ganglion enter the midpontine level at the basis pontisand will synapse in respective nucleus of the CN V depending on the type ofsensation.

! Pain and temperature sensation descends in the brainstem to form the SpinalTrigeminal Tract and will synapse in Spinal Trigeminal Nucleus

! Light touch and crude touch sensation will synapse in the Main Sensory Nucleus

! Proprioception or joint sensation from Temporomandibular joint are segregatedand will ascend in the brainstem to synapse in the Mesencephalic Nucleus ofCNV

Nucleus

! Mesencephalic Nucleus (2nd Order Neuron) Process proprioception

Similar to Cuneate and Gracile Nucleus

! Main Sensory Nucleus (2nd Order Neuron)

Process Light touch and crude touch

! Spinal Nucleus (2nd Order Neuron) Process pain and temperature sensation

Continuous with the Substantia gelatinosa of the spinal cord

It also receive fibers from CN VII, IX and X

! Motor Nucleus

Receive bilateral inputs from CBT

Controls the muscles of mastication

Trigeminothalamic Tract (TTT) ! Axons of the trigeminal nucleus decussate on the contralateral side and will

ascend in the brainstem to form the Trigeminothalamic tract to terminate in theVPM of the thalamus

Ventral TTT

Axons of the spinal and main sensory nucleus

Similar to Spinothalamic Tract of the Spinal Cord

Dorsal TTT

Axons of the mesencephalic nucleus

Some axons will pass the brachium conjunctivum to terminate inthe cerebellar hemisphere and majority will ascend andterminate in the VPM of the thalamus

Similar to Dorsal Column of the Spinal Cord

VPM of Thalamus

! Sensory relay station of Trigeminothalamic Tract ! Axons of VPM projects to Area 312 in the Sensory Homunculus supplying the

face and neck

Summary: Pain and Temperature > Trigeminal Ganglion (1st Order) > Spinal Trigeminal Nucleus (2nd

Order) > VPM of Thalamus (3rd Order) > Area 312 Light touch and Crude Touch > Trigeminal Ganglion (1st Order) > Main Sensory Nucleus (2nd

Order) > VPM of Thalamus (3rd Order) > Area 312 Proprioception > Trigeminal Ganglion (1st Order) >Mesencephalic Nucleus (2nd Order) > VPM

of Thalamus (3rd Order) > Area 312

G. FacialNucleus:

Motor Nucleus of CN VII ! Located at the pons

! 2 Regions Dorsal nucleus

Receive bilateral fibers of CBT

Controls the upper quadrant of the ipsilateral face Ventral nucleus

Only supplied by the contralateral CBT

Controls the lower quadrant of the ipsilateral face Superior Salivary Nucleus

! Parasympathetic Nucleus of CN VII




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! Supply the Lacrimal Gland via the Vidian Nerve ! Supply the Submandibular and Sublingual Glands via Chorda Tympani

Nucleus Tractus Solitarius ! Neuron shared by CN VII, IX, X ! Caudal Nucleus: Baroreceptor, Respiratory and Chemoreceptor ! Rostral Nucleus: Taste Sensation

Project in VPM of Thalamus via Solitariothalamic Tract (Uncrossed) CN VII: Supply anterior 2/3 of the tongue

Spinal Nucleus of Trigeminal Nerve Nerve

Motor Nerve of CN 7 ! Carrying the fibers of the motor nucleus to innervate the facial muscles

Nervus Intermedius ! Bears the fibers of the Nucleus Tractus Solitarius and Superior Salivary Nucleus

Nerve fibers of CN VII loop around the nucleus of CN VI forming the facial colliculus at theposterior pons. The fibers, both motor nerve and nervus intermedius, then emerge at theanterior brainstem at the pontomedullary junction.

Both nerves will enter the internal acoustic meatus. Inside the internal acoustic meatus, thenerve will form the Geniculate Ganglion. Geniculate ganglion is similar to dorsal root ganglion

and trigeminal ganglion. Instead of pain sensation, it will carry taste sensation coming fromthe anterior 2/3 of the tongue, which will be delivered to the nucleus tractus solitarius.

Inside the internal acoustic meatus, 3 branches will emerge (from proximal to distal): ! Greater Petrosal Nerve

Will give rise to Vidian Nerve which will supply the lacrimal glands for tearsecretion (secretomotor)

! Nerve to Stapedius Supply the Stapedius Muscle

! Chorda Tympani Will carry both fibers of inferior salivary nucleus and nucleus tractus solitarius It will supply the anterior 2/3 of the tongue and secretomotor to the

submandibular and sublingual gland As the nerve exits the external acoustic meatus, it will now carry pure fibers of the motor

nucleus. Facial nerve this time will divide into 5 branches as it pierces the parotid gland. Thenerve then supplies the muscles of facial expression.

! Temporal Branch ! Zygomatic Branch ! Buccal Branch ! Marginal Mandibular Branch ! Cervical Branch

Some clinical correlation: (My dear students, please learn this by heart) Any lesion affecting the facial nerve will always result in facial paralysis. Lesion affecting the facial nerve before it enters the internal acoustic meatus will affect all the

functions of the facial nerve.! Dryness of the ipsilateral eye (affectation of the vidian nerve)

! Ipsilateral Hyperacusis- normal sounds perceived as loud (affectation of the nerve tostapedius) ! Ipsilateral dryness of mouth and loss of taste sensation (affectation of the chorda

tympani) ! Ipsilateral facial paralysis (both upper and lower quadrant)

Any lesion affecting the facial nerve distal to geniculate ganglion will spare the vidian nerve Lesion distal to nerve to stapedius and distal to external acoustic meatus will spare the vidian

nerve and the nerve to stapedius Lesion distal to chorda tympani will spare taste sensations, stapedius function and lacrimal

gland function Lesion affecting any part of the Corticobulbar tract will spare the motor function on the

contralateral upper quadrant.

H. VestibulocochlearWill be discussed in Eye and Auditory Pathway, Vestibular Pathway

I. GlossopharyngealNucleus:

Nucleus Ambiguus ! Special motor nucleus shared by CN IX, X, XI which supplies the pharyngeal and

laryngeal muscles Inferior Salivary Nucleus




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! Parasympathetic Nucleus that will control the secretion of the Parotid Gland

Nucleus Tractus Solitarius ! Shared by CN VII, IX, X ! Relay taste sensation to the posterior 3rd of the tongue ! Relay station of the carotid sinus

Spinal Nucleus of Trigeminal Nerve Nerve:

Arises at the sides of the upper medulla The Nerve will be transmitted by the jugular foramen together with the Vagus nerve and

Spinal Accessory Nerve to Jacobson: branch of CN IX supplying sensation to the tympanic membrane Supplies the Stylopharyngeus muscle and secretomotor to the parotid gland

J. VagusNucleus:

Nucleus Ambiguus ! Controls the following muscles:

Salpingopharyngeus Levator Veli Palatini Palatoglossus

Palatopharyngeus Superior, Middle and Inferior Pharyngeal Constrictor Stylopharyngeus Cricothyroid

Nucleus Tractus Solitarius ! Shared by CN VII, IX, X ! Relay taste sensation to the root of the tongue and pharynx

Dorsal Motor Nucleus ! Parasympathetic Preganglionic Nucleus of CN X ! Supply the Viscera of the thorax and abdominal cavity (lungs, heart, GIT, GUT)

Nerve: Emerges at the sides of the upper medulla Transmitted by the jugular foramen together with CN IX, X, XI

Branches: ! Auricular! Pharyngeal! Superior Laryngeal! Recurrent Laryngeal ! Cardiac ! Pulmonary ! Esophageal

K. AccessoryNucleus:

Nucleus Ambiguus ! Shared by Cranial nerve IX, X and XI in controlling the muscles of the pharynx

Spinal Accessory Nucleus

! Motor Nucleus controlling the Sternocleidomastoid and Trapezius Nerve:

Together with CN IX and X, exits the intracranial cavity via the Jugular Foramen ! Cranial Portion

Travels with CN X to supply the larynx ! Spinal Portion

To SCM and Trapezius

L. HypoglossalNucleus:

Hypoglossal Nucleus ! Motor nucleus supplied by contralateral CBT only

Nerve:

Arises at the medulla oblongata Innervates the tongue and posterior digastric muscles except palatoglossus which is

supplied by CN X Lesion of the nerve will deviate the tongue towards the side of the lesion. (the tongue will

point to the lesion)

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Brainstem and Cranial Nerves