Brainstem and Cranial Nerves
Transcript of 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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Neuroanatomy: Brainstem and Cranial Nerves
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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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Neuroanatomy: Brainstem and Cranial Nerves
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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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Neuroanatomy: Brainstem and Cranial Nerves
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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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Neuroanatomy: Brainstem and Cranial Nerves
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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
Vestibulospinal 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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Neuroanatomy: Brainstem and Cranial Nerves
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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
Vestibulospinal Tract
Spinal Trigeminal and Trigeminothalamic Tract Cavity:
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
Spinal Trigeminal and Trigeminothalamic Tract Cavity:
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 Longitudinal Fasciculus
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 Longitudinal Fasciculus
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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Neuroanatomy: Brainstem and 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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Neuroanatomy: Brainstem and Cranial Nerves
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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)