CRANIAL NERVES 1-6
PRESENTED BY:
DR. AYUSHI GUPTA
MODERATOR:
DR. JITENDER PHOGAT
Department of Oral and Maxillofacial Surgery
1
CONTENTS
1. INTRODUCTION
2. EMBRYOLOGY
3. NEUROANATOMY
4. OLFACTORY NERVE
5. OPTIC NERVE
6. OCCULOMOTOR NERVE
7. TROCHLEAR NERVE
8. ABDUCENT NERVE
9. TRIGEMINAL NERVE
15. REFERENCES
2
INTRODUCTION
3
Nervous System
Central Nervous
System
Brain
Spinal cord
Peripheral
Nervous System
Cranial nerves
Spinal nerves
4
CLASSIFICATION
5
SENSORY
MOTOR
MIXED
• I OLFACTORY
• II OPTIC
• VIII VESTIBULOCOCHLEAR
•
•
•
•
•
III OCCULOMOTOR
IV TROCHLEAR
VI ABDUCENT
XI ACCESSORY
XII HYPOGLOSSAL
• V TRIGEMINAL
• VII FACIAL
• IX GLOSSOPHARYNGEAL
• X VAGUS
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EMBRYOLOGY
7
8
9
10
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NEUROANATOMY
12
13
14
OLFACTORY NERVE CN-I
15
SENSORY
CRANIAL
NERVE I
SPECIAL
AFFERENT
OLFACTORY
NERVE
OLFACTORY
MUCOSA
SMELL
NASAL
CAVITY
16
• Shortest cranial nerve. It is a special visceral afferent
nerve, which transmits information relating to smell.
• Embryologicallly, it is derived from the olfactory placode (a
thickening of the ectoderm layer), which also give rise to the
glial cells which support the nerve.
• The olfactory nerves, about 20 in number, represent
central processes of the olfactory cells.
17
Olfactory mucosal layer senses smell and detects advanced aspects of taste.
It is composed of pseudostratified columnar epithelium which contains a
number of cells:
Basal cells – Cells from which the new olfactory cells can develop.
Sustentacular cells – tall cells for structural support. Analogous to the glial cells
located in the CNS.
Olfactory receptor cells – bipolar neurons with two processes:
Dendritic process projects to the surface of the epithelium, where they
project a number of short cilia, the olfactory hairs, into the mucous membrane.
These cilia react to odors in the air and stimulate the olfactory cells.
Central process (also known as the axon) projects in the opposite direction
through the basement membrane.
Bowman’s glands :Present in the mucosa, which secrete mucus.
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19
Nasal Epithelium: Olfactory receptors detects smell.
Their axons (fila olfactoria) assemble into small bundles of true olfactory nerves, which
penetrate the small foramina in the cribriform plate of the ethmoid bone and enter the
ant. cranial cavity.
•Olfactory Bulb
•It is an ovoid structure in the olfactory groove within the anterior cranial fossa which
contains specialised neurons, called mitral cells.
• The olfactory nerve fibres synapse with the mitral cells, forming collections known
as synaptic glomeruli. From the glomeruli, second order nerves then pass posteriorly
into the olfactory tract.
20
•Olfactory Tract
•The olfactory tract travels posteriorly on the
inferior surface of the frontal lobe. As the tract
reaches the anterior perforated substance (an area
at the level of the optic chiasm) it divides into
medial and lateral stria:
•Lateral stria – carries the axons to the primary
olfactory cortex, located within the uncus of
temporal lobe.
•Medial stria – carries the axons across the medial
plane of the anterior commissure, where they
meet the olfactory bulb of the opposite side.
•The primary olfactory cortex sends nerve fibres to
many other areas of the brain, notably the
piriform cortex, olfactory tubercle and the
secondary olfactory cortex. These areas are
involved in the memory and appreciation of
olfactory sensations.
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22
Olfactory Nerve Examination
First, the patient should be asked if
they have noticed any changes in
their taste or sense of smell.
Each nostril should be tested, asking
the patient to identify a certain
smell (peppermint or coffee are often
used). The eyes should be closed for
this part of the examination.
23
Anosmia
Absence of the sense of smell.
Causes:
Temporary: caused by infection (e.g. meningitis) or by local disorders of the nose
(e.g. common cold)
Permanent: by head injury, or tumours in the olfactory groove (e.g. meningioma).
Progressive: Neurodegenerative conditions, such as Parkinson’s or Alzheimer’s
disease. It precedes motor symptoms and is often not noticed by the patient.
Genetic conditions:
Kallmann syndrome and Primary Ciliary Dyskinesia (defect in cilia causing it to
be immobile)
24
HEAD INJURY: Olfactory bulbs may be
torn away from olfactory nerves as
these
pass
through
fractured
cribriform plate. May be associated
with CSF rhinorrhoea.
In 13% patients with mild head injury, 11%
with moderate head injury and 25% with
severe head injury were totally anosmic.
Mechanisms of post-traumatic olfactory
disturbances
(1) sinonasal tract disruption
(2) direct shearing or stretching of
olfactory nerve fibers at the cribiform
plate, and
(3) focal contusion or hemorrhage within
the olfactory bulb and cortex.
Evaluation:
History & physical examination.
Nasal endoscopy, CT scan, MRI scan.
Measurement of Chemosensory Function:
Alcohol sniff test, e CCRC, UPSIT, and Sniffin’ Sticks
test systems.
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OPTIC NERVE CN-II
26
SENSORY
CRANIAL
NERVE II
SPECIAL
AFFERENT
OPTIC NERVE
RETINA OF
THE EYE
Total length: 47-50mm
Intraocular part:1mm
Intraorbital part: 30mm
Canalicular part: 6-9mm
Intra cranial part: 10mm
VISION
27
o It is made up of the axons of cells in the ganglionic layer
of the retina.
o It emerges from the eyeball and runs backwards and
medially.
o It passes through the optic canal to enter the middle
cranial fossa where it joins the optic chiasma.
o Extension of the white matter of brain and thus
considered as part of the CNS; examination of the nerve
enables an assessment of intracranial health.
o Covered by 3 meninges with subdural and subarachnoid
spaces.
o Presence of plial sheaths providing rich blood supply.
28
29
Extracranial course
Formed by the convergence of axons from the retinal ganglion cells. These cells in turn
receive impulses from the photoreceptors of the eye (the rods and cones).
After its formation, the nerve leaves the bony orbit via the optic canal, a passageway
through the sphenoid bone. It enters the cranial cavity, running along the surface of
the middle cranial fossa (in close proximity to the pituitary gland).
Within the middle cranial fossa, the optic nerves from each eye unite to form the optic
chiasm. At the chiasm, fibres from the nasal (medial) half of each retina cross over to the
contralateral optic tract, while fibres from the temporal (lateral) halves remain ipsilateral:
Left optic tract – contains fibres from the left temporal (lateral) retina, and the right nasal
(medial) retina.
Right optic tract – contains fibres from the right temporal retina, and the left nasal retina.
Optic chiasma:
Flattened and quadrilateral bundle of nerves at junction of floor and anterior wall of third ventricle.
Antero-lateral angles- optic nerve
Postero-lateral angles- optic tract
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Each optic tract travels to its
corresponding cerebral hemisphere
to reach the lateral geniculate
nucleus (LGN), a relay system
located in the thalamus; the fibres
synapse here.
Axons from the LGN then carry
visual information via a pathway
known as the optic radiation.
Detached oval /kidney shaped part of thalamus
with the hilum ventrally.
6 layered from hilum to periphery.
Total no. of cells 1 million.
31
Optic radiation: The pathway itself can be divided into:
Upper optic radiation – carries fibres from the superior retinal
quadrants (corresponding to the inferior visual field quadrants). It
travels through the parietal lobe to reach the visual cortex.
Lower optic radiation – carries fibres from the inferior retinal
quadrants (corresponding to the superior visual field quadrants).
It travels through the temporal lobe, via a pathway known as
Meyers’ loop, to reach the visual cortex.
Once at the visual cortex, the brain processes the sensory data
and responds appropriately.
32
VISUAL PATHWAY
33
Second neurons:
First neurons:
Bipolar cells of neuron
Transmit information
from rods and cones to
ganglionic cells of inner
part of retina
One ganglionic cell is
connected to 300 rods
and 10 cones
Ganglionic cells of retina
Third neurons:
Axons form in succession
optic nerve, chiasma and
tract.
Cells in six layers of lateral
geniculate body.
Temporal fibers pass
uncrossed, nasal fibers
decussate.
Optic tract contains -Temporal half of the same
retina and nasal half of the
opposite retina.
53% of fibers decussate to
opposite side.
Crossed fibers synapse with:
Layers 1, 4, 6
Uncrossed fibers synapse
with: Layers 2, 3, 5
Axons of third neuron
project to striate area ( area
17 ) of visual cortex through
optic radiation.
34
Optic nerve
Examination
Visual field & acuity Test:
Acuity is the ability to
discern the shapes and
details of the things you
see.
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36
COMPLETE LESION OF OPTIC NERVE
Total blindness of the corresponding eye.
Loss of pupillary light reflex on the affected side and consensual reflex on the sound side.
Retention of consensual reflex on the blind eye and direct reflex on sound eye.
Accomodation reflex remains unaffected.
WHEN A TUMUOR AFFECTS THE BASE OF FRONTAL LOBE , IT MAY PRESS UPON OPTIC NERVE
(Foster Kennedy Synd)
-Optic atrophy on the affected side, due to pressure.
-Choked disc on the sound side , due to increased intra cranial tension.
TUMOR OF HYPOPHYSIS (MIDLINE LESION)
BITEMPORAL HEMIANOPIA– Interruption Of Crossed Nasal Fibres Of Both Retinae.
BITEMPORAL UPPER QUADRANTIC HEMIANOPIA– Initial stage Of Tumour, inferior nasal fibres involved.
BINASAL HEMIANOPIA– Interruption of non-deccusating fibres on both sides.
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CONTRALATERAL HOMONYMOUS HEMIANOPIA
Unilateral complete obliteration of optic tract or geniculate body or optic radiation.
CONTRALATERAL UPPER OR LOWER QUADRANTIC HOMONYMOUS HEMIANOPIA
Partial Lesion Involving Visual Cortex.
UPPER QUADRANTIC HEMIANOPIA
Lesion in the temporal lobe involving meyer’s loop.
ARGYLL-ROBERTSON PUPIL
Lesion of pre tectum. Loss of light reflex but the near reflex is retained.
38
RETROBULBAR HEMATOMA
Direct injury or forces transmitted to the globe by displaced fracture segments can result in retrobulbar
hematoma, globe rupture, lens displacement, vitreous hemorrhage, retinal detachment, and optic
nerve injury.
Due to Bleeding within a relatively closed compartment and the lack of a potential drainage pathway.
Clinical features:
Significant pain, proptosis, marked upper lid swelling, restricted extraocular motions, and/or any decrease
in vision. Exophthalmos and excessive tension of the lid.
No visual deterioration or increase in IOP: Conservative management with ice cold compresses can be
used.
Elevation of intra-orbital pressure: central retinal artery compression, or ischemia of the optic nerve.
Immediate surgical management:
Evacuation consists of a lateral canthotomy, with or without inferior cantholysis, and disinsertion of the
septum along the lower eyelid in a medial direction.
A small drain is left in place for 24 to 48 hours to ensure adequate drainage and to prevent reaccumulation.
Additional maneuvers to lower the intraocular pressure include administration of intravenous mannitol or
39
acetazolamide or application of various glaucoma medications.
OCULOMOTOR NERVE CN-III
40
MOTOR
ACCOMODATION
GENERAL
SOMATIC
EFFERENT
CRANIAL
NERVE III
CONTRACTION
OF PUPIL
OCULOMOTOR
NERVE
GENERAL
VISCERAL
EFFERENT
MOVEMENT
OF EYE
MUSCLES OF
EYE
GENERAL
SOMATIC
AFFERENT
41
DEEP ORIGIN (NUCLEAR ORIGIN)
Occulomotor Nuclear Complex is a
combination of general somatic efferent
and general visceral efferent columns.
LOCATION:
Ventro medial part of the periaqueductal
central grey matter of the midbrain at the
level of superior colliculus.
INTRANEURAL COURSE:
Fibers from nucleus pass ventrally through the
tegmentum, red nucleus and substantia nigra.
The nerve passes b/w superior cerebellar and
posterior cerebral arteries and runs towards
interpeduncular cistern to reach cavernous
sinus.
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43
The nerve enters cavernous sinus by piercing the posterior part of its roof on
lateral side of posterior clinoid process.
In lateral wall of sinus it lies above trochlear nerve and divides into 2 branches in
the anterior part of sinus.
The two divisions enter the orbit through middle part of superior orbital fissure.
44
SUPERIOR RAMUS
Passes forward & upward lateral to optic
nerve
Supplies Superior rectus & levator palpebrae
superioris
INFERIOR RAMUS
Divides into 3 branches:
a) Passes mediallly below optic nerve to
Medial rectus
b) Directly to inferior rectus
c) Longest branch supplies Inferior oblique &
communicating branch to ciliary ganglion.
45
CILLIARY GANGLION
Peripheral parasympathetic ganglion
Topographically- nasocilliary nerve
Functionally- occulomotor nerve
Contains multipolar neurons.
LOCATION:
Near the apex of orbit
Between optic nerve & lateral rectus muscle
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A) Motor (preganglionic,
parasympathetic) root:
b) Sensory (postganglionic
sympathetic) root:
Arise from the nucleus of
EDINGER WESTPHAL.
Derived from nasociliary
nerve
Axons course with the
fibres of occulomotor nerve
to cilliary ganglion.
Also carry postganglionic
fibres from cell bodies
Synapse with
postganglionic fibres in
ganglion (short cilliary
nerves).
Innervate sphincter
pupillae and cilliary muscles
of iris.
of the superior cervical
sympathetic ganglion.
Concerned with pain,
touch, thermal
c) Sympathetic root:
Derived from internal
carotid plexus.
Supply blood vessels to the
eyeball.
Pass through without
synapse to innervate
dialator pupillae muscle in
iris.
sensations to eyeball.
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OCULOMOTOR NERVE
EXAMINATION
48
APPLIED ANATOMY:
COMPLETE DIVISION OF OCCULOMOTOR NERVE ON ONE SIDE
Ptosis or drooping of the upper eyelid
External strabismus(squint)Dilated or fixed pupil
Loss of accommodation
Apparent protrusion of eyeball- flaccid paralysis of ocular muscles.
Diplopia
PERIARTERITIS( MANIFESTATION OF NEUROSYPHILLIS)
Posterior cerebral and superior cerebellar arteries
Micro aneurysm of posterior communicating artery
Ipsilateral lower motor neuron paralysis of occulomotor nerve AND
Contra lateral upper motor neuron paralysis of the body due to
Interruption of the corticospinal tract of basis peduncle –WEBER’S SYNDROME.
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TROCHEAR NERVE CN-IV
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MOTOR
GENERAL
SOMATIC
AFFERENT
CRANIAL
NERVE IV
TROCHLEAR
NERVE
GENERAL
SOMATIC
EFFERENT
PROP. FROM
SUPERIOR
OBLIQUE
SUPERIOR
OBLIQUE
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• Only cranial nerve emerging from
dorsal aspect of the brain.
• Most cylindrical nerve with of least
number of fibres (neurons).
• Only peripheral nerve undergoing
complete deccusation to opposite side
before emerging from brainstem.
• Nerve with the longest intracranial
course.
Nucleus:
Situated in the ventromedial part of
central gray matter of mid brain at the
level of inferior COLLICULUS.
52
Intraneural course: nerve runs dorsally round the central grey
matter to reach the upper part of the superior or anterior
medullary velum where it decussates with the opposite nerve
to emerge on the opposite side.
Surface Attachment:
Trochlear nerve is attached to superior medullary velum on
each side
Only nerve that emerges on the dorsal aspect of the
brainstem.
53
• The nerve winds round the superior cerebral
peduncle just above the pons.
• It passes between the posterior cerebral and
superior cerebellar arteries to appear ventrally
between the temporal lobe and upper border of
pons
• The nerve enters the of cavernous sinus by
peircing the posterior corner of its roof.
• It runs forward in its lateral wall between
occulomoter and opthalmic nerves.
• It then enters the orbit through the lateral part of
the superior orbital fissure.
• In the orbit, it passes medially, above the origin of
levator palpebrae superioris and supplies superior
oblique muscle.
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Applied anatomy
Test of examination: Same as of occlomotor nerve.
IF TROCHLEAR NERVE IS INJURED
Patient is unable to turn his eye downward and laterally.
NO difficulty in looking above horizontal plane.
On attempting to look down, double vision is seen.
To avoid, patient tilts his head forwards towards the sound side.
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TRIGEMINAL NERVE CN-V
56
MIXED
CRANIAL
NERVE V
MOTOR
ROOT
SENSORY
ROOT
TRIGEMINAL
NERVE
OPHTHALMIC
BRANCH
MANDIBULAR
BRANCH
MAXILLARY
BRANCH
57
The trigeminal nerve is the largest and most
complex of the 12 cranial nerves (CNs). It
supplies sensations to the face, mucous
membranes, and other structures of the
head. It is the motor nerve for the muscles of
mastication and also contains proprioceptive
fibers.
58
GASSERION GANGLION
The trigeminal ganglion ( Gasserian
ganglion/semilunar ganglion/Gasser's ganglion) is a
sensory ganglion of the trigeminal nerve (CN V) that
occupies a cavity (Meckel's cave) in the dura mater,
covering the trigeminal impression near the apex of
the petrous part of the temporal bone.
59
SENSORY ROOT OF TRIGEMINAL NERVE
Fibres arise from the semilunar ganglion.
Enter brainstem through side of pons.
CENTRAL BRANCHES
(SENSORY ROOTS OF NERVE)
ASCENDING FIBRES
Terminate in UPPER sensory nucleus
In pons lateral to motor nucleus.
DORSAL TRIGEMINOTHALMIC
TRACT
CONVEY:
Light touch
Tactile discrimination
Sense of position
Passive movement
DESCENDING FIBRES
Terminate in SPINAL nucleus
extending caudally from upper
sensory nucleus to 2nd cervical
segment.
VENTRAL TRIGEMINO-THALAMIC
TRACT
CONVEY:
Pain
Temperature
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61
Motor Root
•Fibres originate from motor nucleus in upper pons.
• These, then pass along medial side of semilunar
ganglion
•Passes below foramen ovale
•Joins Mandibular division below base of skull
•Supplies muscles of mastication, thus is often called
masticatory nerve.
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Mesencephalic Root
1st synapse
During mastication proprioceptors in muscles tendons, pdl, teeth, palate &
joints send impulses through afferent fibres that enter brain stem, pass through
mesencephalic nucleus & synapse in main nucleus of the nerve.
2nd synapse
Fibres constitute the dorsal trigemino-thalamic fibres of bulbo-thalamic tract.
They carry tactile perception from afferent fibres of the nerve
3rd synapse
Occurs as afferent fibres leave thalamus & proceed to post central gyrus in the
cortex.
They permit awareness of motion in jaws & position of mandible and maxilla
during chewing movements.
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64
OPTHALMIC NERVE
65
Smallest division.
Originates from ant. Medial part of semilunar ganglion ,runs along lateral wall of cavernous
sinus.
Sensory fibres from:
Skin, scalp of forehead, upper eyelid lining frontal sinus, conjuctiva of eye, lacrimal gland,
skin of lateral angle of eye ball & lining of ethmoid cell.
66
LACRIMAL NERVE
Passes into orbit at lateral Angle of sup. Orbital fissure. Courses anterolaterally to
reach lacrimal gland & SUPPLIES Lacrimal Gland & Adjacent Conjunctiva.
FRONTAL NERVE
Supraorbital
Exits orbit by supraorbital foramen.
Supplies skin of upper lid,forehead, ant. Scalp to vertex of scull.
Supratrochlear
Passes towards medial angle of orbit & pierces the fascia of upper eyelid.
Supplies: skin of upper eyelid & lower medial portion of forehead
NASOCILIARY NERVE
Enters the orbit through superior orbital fissure
67
Nasociliary
nerve
In orbit
•Long root of ciliary
ganglion.
•Long ciliary nerves.
•Posterior Ethmoid
Nerve.
•Anterior ethmoid
nerve.
In nasal
cavity
•Supply the mucous
membrane lining the
nasal cavity
On face
Sensory fibres to skin
Medial part of both eyelids
Lacrimal sac
Lacrimal caruncle
Side of bridge of nose
68
MAXILLARY NERVE
69
70
Transmits afferent impulses from:
• Upper lip
• Lower eyelid
• Tonsillar region
• Side of the nose
• Hard and soft palate
• Lining of maxillary sinus
• Opening of eustachian tubes
• All maxillary teeth and gingiva
• Mucous membrane of the nasal cavity
71
Course:
Intracranial part:
Originates in the middle part of semilunar ganglion
Passes forward in lower part of cavernous sinus
Exits through foramen rotundum.
Extracranial part:
 Enters pterygopalatine fossa.
 Enters inferior orbital fissure to enter orbital cavity.
 Runs laterally along infra orbital groove.
 Emerges through infra orbital foramen.
72
BRANCHES IN PTERYGOPALATINE FOSSA
A. ZYGOMATIC NERVE:
Passes anteriorly and laterally through inferior orbital fissure into orbit.
1. ZYGOMATICOFACIAL NERVE:
Supplies skin over prominence of zygomatic bone
2. ZYGOMATICOTEMPORAL NERVE:
Supplies sensory fibres to skin over anterior temporal fossa
B. PTERYGOPALATINE {SPHENOPALATINE} NERVES:
2 short nerve trunks that unite at the pterygopalatine ganglion.
Most of the fibres pass through the ganglion without synapse.
Postganglionic secretomotor fibres pass back along maxillary nerve to zygomatic
nerve to supply Lacrimal nerve and gland.
73
 BRANCHES:
ORBITAL : Enter The Orbit Through Inferior Orbital Fissure.
Supply:
Periosteum of orbit
Mucous membrane of part of posterior ethmoid cells
Sphenoid sinus
NASAL:
Posterior Superior Lateral Nasal Br.
Supplies mucous membrane of posterior ethmoid cells and nasal septum.
Medial Or Septal Br.
Supplies premaxillary region over hard palate and mucous membrane over vomer.
PALATINE:
Gr. or anterior palatine br:
Supplies major part of hard palate and palatine gingivae.
Middle Palatine Br.
Supplies mucous membrane of soft palate.
Posterior palatine br.
Supplies mucous membrane of the tonsillar area.
74
C.
POSTERIOR SUPERIOR ALVEOLAR NERVES:

Leave main branch before it enters inferior orbital fissure.

Enter post. superior alveolar canal along with internal maxillary artery.

Supplies:
Sensory to mucous membrane of sinus
Maxillary teeth and its gingivae.
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BRANCHES IN INFRAORBITAL GROOVE AND CANAL:
1. MIDDLE SUPERIOR ALVEOLAR NERVE
 Leaves in posterior part of floor of Infraorbital canal.
 Passes downward and anterior over the anterolateral wall of maxillary sinus.
 Supplies maxillary bicuspids.
2. ANTERIOR SUPERIOR ALVEOLAR NERVE
 Descends from main trunk just inside infra orbital foramen.
 Passes through fine canals in maxilla
 Supplies:
Incisors and cuspids
Anterior Part of maxillary sinus
Labial gingiva of incisors and cuspids
76
As the infraorbital nerve is about to emerge from the foramen in front of maxilla it
divides into:
3 TERMINAL BRANCHES ON FACE:
INFERIOR PALPEBRAL BRANCH.
LATERAL NASAL BRANCH
SUPERIOR LABIAL BRANCH
77
PTERYGOPALATINE GANGLION
SENSORY:
Two Sphenopalatine branches of maxillary
nerve. Fibres pass directly into palatine
Nerves.
SYMPATHETIC:
Derived from carotid plexus through
deep petrosal nerve. Forms nerve to
pterygoid canal.
MOTOR:
Derived from nervous intermedius
through greater superficial petrosal Nv.
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MANDIBULAR NERVE
79
Sensory root Supplies:
Dura
External ear
Parotid gland
TMJ articulation
Lower teeth and gingiva
Scalp over temporal region
Ant. 2/3rd of the tongue.
skin and mucous membrane of
chin,
cheek & lower lip.
Motor root supplies:
Muscles of mastication.
Course and distribution




Motor root is located in
middle cranial fossa
Sensory root emerges from
semilunar ganglion
2 roots pass alongside in
cranium.
Emerging from foramen
ovale, they unite.
80
81
Branches from undivided nerve:
a.) Nervous spinosus
Arises outside the skull and then
passes in the middle cranial fossa to
supply dura and mastoid cells.
b.) Nerve to internal pterygoid
A branch passes to innervate
internal pterygoid muscle. A sub
branch passes for tensor veli palatini
and tensor tympani muscles.
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Branches from divided nerve:
ANTERIOR DIVISION:
A.) Pterygoid Nerve:
Enters the medial side of external
pterygoid muscle for its motor
supply.
B.) Masseter Nerve:
Passes above the external
pterygoid to traverse the
mandibular notch and
enter the deep side of
masseter muscle.
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D.) BUCCAL NERVE:
Passes downwards, anteriorly
and laterally between the two
heads of external pterygoid
muscle.
AT THE LEVEL OF OCCLUSAL PLANE,
IT RAMIFIES to give:
Motor& sensory innervation to
cheek
Sensory fibres to retromolar pad
&buccal gingivae
OCCASIONALLY:
Nerve supply to 2nd bicuspid & 1ST
molar
84
Posterior division
Auriculotemporal
nerve: OF
BRANCHES
AURICULOTEMPORAL
Arises
by a medial and a lateral root.
NERVE
Courses upward &posteriorly,
PAROTID
BRANCHES::
Secretory,
sensory
Deep
to external
pterygoid
muscle.
and vasomotor fibres to the gland.
B/w. sphenomand. Lig. & neck of
ARTICULAR
BRANCHES:: Sensory Twigs
condyle.
Entering The Posterior Part Of TMJ.
Crosses posterior root of zygomatic arch
AURICULAR BRANCHES:: Sensory fibres
and gives off following branches.
supplying the skin of the helix and tragus.
MEATAL BRANCHES:: Supply the skin of
the meatus and tympanic membrane.
TERMINAL BRANCHES:: Supply scalp over
the temporal region.
85
LINGUAL NERVE
Course:
In pterygomandibular space it Lies
b/w int. pterygoid and ramus
parallel and medio anterior to IAN .
Communications of lingual
nerve with chorda tympani:
Descends down and medially from
side of tongue below lateral lingual
sulcus and loops around
submandibular duct and gives
sensory branches to mucosa of
floor of mouth and gingiva on
As the nerve passes medially to
external pterygoid muscle, its
joined by corda tympani, which
conveys secretory fibres from
facial nerve. This provides taste
sensation to ant 2/3rd of tongue.
lingual side of mandible.
Occasionally may give sensory fibres
to bicuspids and 1st molars.
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Inferior alveolar nerve:
Largest branch of the posterior division.
Passes downwards, medial to external
pterygoid and ramus to
Enter mandibular foramen and
supplies: Dental pulp of teeth
through apical fibres, pdl
&mucoperiostium.
Reaches mental foramen and gives off 2 terminal
branches:
Mental nerve
Incisive nerve
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Mylohyoid nerve:
Both sensory & motor fibres.
Continues downward & forward in
mylohyoid groove.
Motor fibres Supply:
Mylohyoid muscle &
Ant. Belly of digastric
 Some Sensory fibres may supply:
Mandibular incisors.
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Submandibular ganglion
Ovoid body suspended from
lingual nerve over
submandibular gland.
Suspended by 2
parasympathetic, preganglionic
nerve trunks with nucleus in
superior salivatory nucleus, part
of chorda tympani nerve
Postganglionic fibres:
Short
Secretory fibres to
submandibular & Sublingual
gland.
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Trigeminal Nerve Examination
• Motor Function:
• Sensory function:
• Test light sensation with cotton
ball bilaterally over:
• Forehead (opthalmic)
• Cheeks (maxillary)
• Chin (mandibular)
•Palpate temporal & masseter
muscles as patient clenches teeth.
• Try to seprate jaws by pushing up
on chin.
•Inability to raise, depress,
protude,retract, deviate the
mandible might suggest impaired
motor function.
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Applied anatomy
TRIGEMINAL NEURALGIA
Tic douloureux
Fothergill’s disease Pain is unilateral (rarely bilateral).
Duration of pain is typically from few seconds
to 1-2 minutes.
Pain may occur several times a day;
patients typically experience no pain
between episodes.
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ETIOLOGY
Compression of the trigeminal nerve root
Primary demyelination disorders
Infiltrative disorders of the trigeminal nerve root, ganglion and nerve
Non-demyelinating lesions of the pons or medulla
Familial trigeminal neuralgia
PATHOGENESIS
Superior cerebellar artery pressing on or grooving the root of nerve causes pressure that results in
focal de-myelinization and hyperexcitability of nerve fibres which fire in response to light touch
resulting in brief episodes of intense pain.
Treatment:
1. Destructive treatment:
Radiofrequency Rhizotomies, Balloon Gangliolysis, Stereotactic Radiosurgery
2. Non destructive treatment:
Medical treatment (Tegretol, Baclofen, Dilantin, etc.)
Microvascular decompression (with initial success rate of 85 to 95%)
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ABDUCENT NERVE CN-VI
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MOTOR
GENERAL
SOMATIC
AFFERENT
CRANIAL
NERVE IV
ABDUCENT
NERVE
GENERAL
SOMATIC
EFFERENT
PROP. FROM
LATERAL
RECTUS
LATERAL
RECTUS
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Contains about 6,600 fibres & one
nerve fibre supplies only 6 muscle
fibres.
Nucleus:
Nucleus situated beneath floor of
fourth ventricle in dorsal part of
pons, beneath facial colliculus.
Motor root of facial nerve loops
around abducent nucleus.
Superficial origin:
Passes forward & downward
through trapezoid body, medial
laminiscus and Basilar part of
pons and appears on upper
border of medulla.
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Course and distribution:
 From the brainstem it passes forwards ,upwards & laterally.
 Lies dorsal to ant. inferior cerebellar artery.
 Pierces dura lateral to dorsum sellae of sphenoid, traverses cavernous sinus infero-lateral to
internal carotid artery.
Enters the orbit through Sup.Orbital fissure within tendinous ring, infero lateral to 3rd &
Nasocilliary nerves and supplies the lateral rectus muscle.
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• Nerve changes direction 3 times:
Downward and forward
Upward, forward and laterally
Straight forward
• Nerve bends twice:
at the lower border of pons
at the upper border of petrous temporal
• Longest intradural course
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Applied anatomy:
Involvement produces paralysis of lateral rectus, resulting in medial or
convergent squint or diplopia.
Nerve is likely to be affected by Increased intracranial pressure due to:
a) Long course of the nerve through cisterna pontis
b) Sharp bending at petrous temporal
c) Downward shift of the brainstem at foramen magnum resulting in
stretching of the nerve.
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UPPER MOTOR NEURON LESION:
Damage to the pontine lateral gaze center.
Inability to abduct the eye past midline gaze. Inability to adduct the eye
opposite to the lesion past midline gaze.
LOWER MOTOR NEURON LESION:
Damage to abducent nucleus or its axons resulting in weakness of
ipsilateral side.
Medially directed eye on the affected side due to unopposed action
of medial rectus
Strabismus
Horizontal diplopia
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REFERENCES
• BD CHAURASIA’S HUMAN ANATOMY, VOL. 3, HEAD AND NECK,
BRAIN FIFTH EDITION
• AK JAIN’S HUMAN PHYSIOLOGY FOR BDS, FOURTH EDITION
• DAVIDSON’S PRINCIPLES AND PRACTICE OF MEDICINE, 12TH
EDITION
• MONHEIM’S LOCAL ANAESTHESIA AND PAIN CONTROL IN
DENTAL PRACTICE, SEVENTH EDITION
• INDERBIR SINGH’S HUMAN EMBRYOLOGY 11TH EDITION
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