Cranial Nerves seminars

2. CRANIAL
NERVEs
Dr.Priyanka shaRma
1st year mds
department of public health dentistry
jss dental college & hospital

3. CONTENTS
• Introduction
- Names of the cranial nerves
- Development of the cranial nerves
- Classification of CN according to Component factors
• Olfactory Nerve
-Olfactory Pathway
-Applied Anatomy
• Optic Nerve
-Visual Pathway
-Applied Anatomy

4. • Occulomotor Nerve
- Introduction
- Edinger Westphal Nucleus
- Applied Anatomy
• Trochlear Nerve
- Introduction
- Applied Anatomy
• Trigeminal Nerve
- Introduction
- Trigeminal Ganglion
- Branches Of Trigeminal Nerve
- Nuclear Origin
- Dermatome Distribution Of Head & Neck

5. • Trigeminal Nerve (cont..)
-Branches
- Opthalmic Nerve
- Maxillary Nerve
- Course Of Maxillary Nerve
- Branches Of Maxillary Nerve
- Area Of Supply
- Mandibular Nerve
- Branches Of Mandibular Nerve
- Area Of Supply
- Distribution Of Branches Of Trigeminal Nerve
- Maxillary Arch
- Mandibular Arch
- Applied Anatomy
- Conclusion

6. • Abducens Nerve
- Introduction
- Applied Anatomy
• Facial Nerve
- Introduction
- Nuclear Origin
- Branches
- Applied Anatomy
- Clinical Evaluation
- Conclusion

7. • Vestibulocochlear Nerve
- Introduction
- Branches
- Vestibular
- Cochlear
- Applied Anatomy
• Glossopharyngeal Nerve
- Introduction
- Branches
- Applied Anatomy
- Clinical Evaluation
- Conclusion

8. • Vagus Nerve
- Introduction
- Course Of Vagus Nerve
- Applied Anatomy
• Accessary Nerve
- Introduction
- Assessing X & XI CNs
- Applied Anatomy
• Hypoglossal Nerve
- Introduction
- Branches
- Applied Anatomy
- Conclusion
 References

9. INTRODUCTION
 Arise from the brain
 Pass through or into the cranial bones (thus cranial
nerves)
 Numbered I to XII roughly in order from top (rostral)
to bottom (caudal).
 Cranial nerves exhibit great variety and functional
specialization.
 All the nerves are distributed in the head and neck
except the X , which also supplies the structures of
thorax & abdomen.

10. Names Of The Cranial Nerves
OLFACTORY NERVE
OPTIC NERVE
OCCULOMOTOR NERVE
TROCHLEAR NERVE
TRIGEMINAL NERVE
ABDUCENS NERVE
FACIAL NERVE
VESTIBULOCOCHLEAR NERVE
GLOSSOPHARYNGEAL NERVE
VAGUS NERVE
ACCESSARY NERVE
HYPOGLOSSAL NERVE

11. DEVELOPMENT
In utero, 6 pharyngeal arches are
designated but the 5th never develops.
Each pharyngeal arch is associated
with a developing cranial nerve or its
branches.
1st arch- CN 5 (V3)
 2nd arch- CN 7
3rd arch- CN 9
4th arch- Superior Laryngeal
Branch of CN 10
6th arch- Recurrent Laryngeal
Branch of CN 10

12. SENSORY/
AFFERENT
OLFACTORY
MOTOR/
EFFERENT
OCCULOMOTOR
MIXTURE
TRIGEMINAL
FACIAL
TROCHLEAR
OPTIC
ABDUCENS
VESTIBULO
COCHLEAR
ACCESSARY
HYPOGLOSSAL
VAGUS
GLOSSO
PHARYNGEAL

13. OLFACTORY NERVE (CN1)

14. OLFACTORY PATHWAY
1st
neuron
2nd
Neuron
• Bipolar neurons – Olfactory Cells
• Olfactory Nerves
• Mitral & tufted cells in the Olfactory bulb  fibers form
OLFACTORY TRACT  Lateral & Medial Olfactory Striae
• Located in Primary Olfactory Cortex (Piriform lobe & Septal
Nucleus)
3rd
Neuron • Anterior Perforated substances & small masses of grey matter
4th
Neuron
• Secondary olfactory cortex
• Located anterior to the parahippocampal gyrus

16. CLINICAL ANATOMY
 Anosmia
-Loss of smell
 Cerebrospinal fluid rhinorrhoea
 Temporal lobe epilepsy
 Kluver Bucy Syndrome

17. OPTIC NERVE (CN2)

18. VISUAL PATHWAY
Bipollar cells
Optic nerve
Optic Canal
Optic Chiasma
Optic Tract
Lateral Geniculate
nucleus
Primary Visual cortex
of Occipital Lobe

19. APPLIED ANATOMY
• Lesion of the optic nerve  Ipsilateral Blindness
• Mid-saggital lesion of the optic chiasma  Bitemporal
Hemianopia
• Lesion of the optic tract  Contralateral Homonymous
Hemianopia
• Lesion of the temporal lobe  Meyer’s loop  Contralateral
Homonymous Upper Quadrantanopia
• Lesion of optic radiation  Contralateral Homonymous
Hemianopia
• Lesion of the visual cortex  Contralateral Homonymous
Hemianopia with Macular Sparing

21. Oculomotor Nerve (CN III)

22. • Origin: Midbrain
• Cranial passage: superior orbital fissure
• Innervates :
- Extra-occular muscles :
1.)Superior, Inferior & Medial Recti Muscles
2.)Inferior oblique Muscle
- Also levator palpabre superioris
• Causes the eye to turn upward, downward and
medially.
• If this nerve is damaged, the action of the remaining
two muscles (superior oblique and lateral rectus)
pulls the eye "down and out” .

23. Edinger-Westphal Nucleus
• Source of the parasympathetics to the eye, which
constrict the pupil and accommodate the lens.
• It is located just inside the oculomotor nuclei.
• The fibers travel in the IIIrd nerve, so damage to that
nerve will also produce a dilated pupil.

24. APPLIED ANATOMY
•
•
•
•
•
•
Lateral strabismus, as medial rectus is paralysed and the
lateral rectus is unopposed.
Diplopia, double-vision as one of the eye deviates from the
midline;
Inability to move the eye medially or vertically;
Ptosis as the ipsilateral levator palpebrae superioris is
paralysed.
Mydriasis (dilated pupil of affected side) and
unresponsiveness to light as the sphincter pupillae is nonfunctional and the dilator pupillae is unopposed;
Inability for the affected eye to focus on near objects as the
ciliary muscles have also been paralysed.

25. PTOSIS
MYDRIASIS
EXOTROPIA
DIPLOPIA

26. Trochlear Nerve (CN IV)

27. •
•
•
•
•
Origin: Midbrain
Supplies : Superior oblique muscle.
Cranial passage : superior orbital fissure
Its cell bodies are located in the contralateral trochlear nucleus.
The superior oblique muscle helps to move the eye downward and
medially (inferomedial).

The trochlear nerve is unique in that:
•
It is the only cranial nerve attached to the dorsal aspect of the
brainstem (exits the brainstem dorsally)
It is the only one to originate completely from the contralateral
nucleus (The fibers cross over each other just like a half-tied
shoelace in the roof of the fourth ventricle)
It is the thinnest and is particularly vulnerable to traumatic injury.
•
•

29. APPLIED ANATOMY
• Damage to the trochlear nerve result in much less drastic and
noticeable deficits than damage to the oculomotor or abducens
nerves.
• Attempted movements in these directions (e.g., reading or walking
down stairs) may cause diplopia.
• Eye points superolaterally.
• This condition often causes vertical double vision as the weakened
muscle prevents the eyes from moving in the same direction
together.
• Bielschowsky's Phenomena :To compensate for the double-vision
resulting from the weakness of the superior oblique, patients
characteristically tilt their head down and to the side opposite the
affected muscle.

30. DIPLOPIA
BIELSCHOWSKY'S
PHENOMENA

31. Trigeminal Nerve (CN V)

32. • Trigeminal or fifth cranial nerve is the largest of the cranial nerves.
• It is a mixed nerve that consists primarily of sensory neurons.
 Sensory nerve Face
 Motor nerve  Muscles of masticaion & several small muscles
• Lies in the floor of the middle cranial fossa, on the petrous temporal
bone.
• It is called trigeminal because it consists of 3 divisions the
ophthalmic nerve (V1), the maxillary nerve (V2), and the
mandibular nerve (V3).
• It forms the trigeminal ganglion from which its three branches
diverge.
 The trigeminal ganglion corresponds to the dorsal root ganglion
of a spinal nerve.

33. Trigeminal Ganglion
• The trigeminal nerve arises from a large semilunar or
trigeminal ganglion which lies in the trigeminal fossa.
• The ganglion is connected to the pons by a thick sensory root.

34. • The trigeminal ganglion (or Gasserian ganglion, or semilunar
ganglion, or 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.

35. Three major branches emerge from the trigeminal ganglion and each branch
innervates a different dermatome :
1.
The ophthalmic nerve (VI) passes along the side of the cavernous sinus to pass
into the orbit through the superior orbital fissure.
2.
The maxillary nerve (V2) passes along the lateral wall of the cavernous sinus to
leave the skull through the foramen rotundum in the sphenoid bone.
3.
The mandibular nerve (V3) passes out of the skull through the foramen ovale.

36. Trigeminal Nerve – Nuclear Origin
There are 4 trigeminal nuclei .
One motor and three sensory nuclei.

37. • The ophthalmic and maxillary nerves are purely sensory.
• The mandibular nerve has both sensory and motor functions.
• Motor part supplies the 4 muscles of mastication ,
mylohyoid , anterior belly of digastric , tensor palati and
tensor tympani .
• Sensory part carries sensations to the scalp, face , teeth ,
gums and anterior two third of tongue.

38. Dermatome of Head & Neck
 OPHTHALMIC NERVE :
1.
Cornea
2.
Skin of forehead
3.
Scalp
4.
Eyelids and nose
5.
Mucous membranes of paranasal
sinuses and nasal cavity
 MAXILLARY NERVE :
1.
Skin of the face over maxilla
2.
Teeth of the upper jaw
3.
Mucous membrane of the nose, the
maxillary sinus and palate
 MANDIBULAR NERVE :
1.
Skin of cheek
2.
Skin over mandible and side of head
3.
Teeth of lower jaw and TMJ
4.
Mucous membrane of mouth and
anterior part of tongue

39. Ophthalmic Nerve - CN ( V1)
• Origin: Anterior aspect of the pons
• Opening to the Skull: Superior orbital fissure
• It has 3 main branches :
* Frontal
* Nasociliary
* Lacrimal

40. OphthalmicDivision (VI)

41. Maxillary Nerve: CN V2
• Other names : n. maxillaris; superior maxillary nerve
• Origin: Anterior aspect of the pons
• Opening to the Skull: Foramen rotundum
• Compostion: sensory
Infraorbital foreman

42. COURSE OF MAXILLARY NERVE
Pterygopalatine Fossa
Lateralward On The Back Of The Maxilla
Enters The Orbit Through The Inferior
Orbital Fissure
It Traverses The Infraorbital Groove And Canal
Appears Upon The Face At The Infraorbital
Foramen

43.  It is divided into four groups :
1. Cranium : Middle meningeal
2. In the Pterygopalatine Fossa : Zygomatic,
Sphenopalatine, Posterior superior alveolar.
3. In the Infraorbital Canal : Anterior superior
alveolar, Middle superior alveolar.
4. On the Face : Inferior palpebral, External nasal,
Superior labial.

44. • The Middle Meningeal Nerve is given off from the
maxillary nerve directly after its origin from the semilunar
ganglion; it accompanies the middle meningeal artery and
supplies the duramater.
• The Zygomatic Nerve arises in the pterygopalatine fossa,
enters the orbit by the inferior orbital fissure, and divides at
the back of that cavity into two branches,
zygomaticotemporal and zygomaticofacial.
• Posterior superior alveolar nerve arise from the trunk of the
nerve just before it enters the infraorbital groove .
• They descend on the tuberosity of the maxilla and give off
several twigs to the gums and neighboring parts of the
mucous membrane of the cheek.

45. • Communicate with the middle superior alveolar
nerve, and give off branches to the lining membrane
of the maxillary sinus and three twigs to each molar
tooth; these twigs enter the foramina at the apices of
the roots of the teeth.

46. • The Middle Superior Alveolar Branch - supply the
two premolar teeth.
• It forms a superior dental plexus with the anterior
and posterior superior alveolar branches.
• The Anterior Superior Alveolar Branch branches
supply the incisor and canine teeth.
• It communicates with the middle superior alveolar
branch, and gives off a nasal branch, which
supplies the mucous membrane of the anterior part
of the inferior meatus and the floor of the nasal
cavity.

47. Mandibular Nerve
• It is the largest of the 3 divisions of trigeminal
nerve.
• It is the nerve of the first branchial arch.
• Origin: Anterior aspect of the pons
• Opening to the Skull: Foramen Ovale
• Composition : Mixed nerve.
• It is formed by a large sensory root and a small
motor root.
• Both roots join to form the main trunk which lies
in the infratemporal fossa. After a short course
the main trunk divides into small anterior and a
large posterior division.

48. BRANCHES OF MANDIBULAR NERVE
1) Branches from the main trunk
a) Meningeal Branch
b) Nerve to medial pterygoid which also
supplies Tensor tympani & Tensor palati.
2) Branches from Anterior division gives rise to 3 motor and one
sensory nerve .
a) Masseteric Nerve
b) Deep temporal Nerves
Motor
c) Nerve to lateral pterygoid
d) Buccal Nerve – only sensory
3) Branches from posterior division – it is predominently sensory
except one branch .
a) Auriculo temporal
b) Lingual
Sensory
c) Inferior alveolar
d) Mylohyoid nerve – only motor.

49. BRANCHES OF MANDIBULAR NERVE

50. V3
provides general sensation to the anterior 2/3 of the tongue
innervates the mucosa of the mouth and gums.
innervates the external auditory
meatus and portions of the
external surface of the tympanic
membrane.
Mental
Foramen
innervate the lower teeth and gums.
chin and lower lip
anterior belly of the
digastric muscle.
nerve to the masseter m , temporalis m.,
medial and lateral pterygoids, tensor palati
and tensor tympani.

51. Sensory Branches of Mandibular
Division (V3)

52. Sensory Branches of Mandibular
Division (V3) cont:
Mandibular
(V3)
Auriculotemporal
Inf. alvolar
Buccal
Mental
Lingual n.

53. Motor Branch of Mandibular Nerve (V3)
Suparhyoid Muscles
Mylohyoid
Anterior Belly Of
Digastric
Muscle Chewing
Masseter
Temporalis
Medial & Lateral
Pterygoid
Tensor Palati
Tensor Tympani

54. Distribution of branches of trigeminal nerve to teeth and
surrounding structures – Maxillary arch
TEETH
T. PULP
GINGIVA
PDL &
ALVEOLAR
PROCESS
HARD PALATE
Anteriors
Ant .Sup alv
nerve
Palatal- Nasoplalatine Ant sup
Labial – Infraorbital
alveolar nerve
& Ant sup Alv nerve
Nasopalatine nerve
Premolars
Middle sup alv
nerve
Palatal – Ant palatine
nerve
Buccal – Middle sup
alv and infraorbital
nerve
Middle
superior
alveolar nerve
Anterior palatine
nerve
Molars
Post sup alv
nerve except
MB root of first
molar
Palatal – Ant palatine
nerve
Buccal – Post sup
alveolar nerve
Post sup
alveolar nerve
Ant palatine nerve
Soft palate –
Middle and post
palatine nerves

55. Mandibular arch
TEETH
DENTAL
PULP
GINGIVA
PDL &
ALV.PRO
LINGUAL
SIDE
Anteriors
Incisive branch
of Inferior alv
nerve
Lingual –
Lingual N
Labial – Mental
N
Incisive N
Lingual N
Premolars
Dental branch of Lingual –
Inferior alv
Lingual N
nerve
Buccal – Mental
N
Dental branch of Lingual nerve
inferior alveolar
nerve
Molars
Dental branch of Lingual –
inferior alveolar Lingual N
nerve
Buccal –
Buccinator N
Dental branch of Lingual nerve
inferior alveolar
nerve

56. APPLIED ANATOMY OF
TRIGEMINAL NERVE

57. Trigeminal Neuralgia
• Trigeminal neuralgia ( tic douloureux ) is a
sensory disorder of CN V that is characterized
by sudden attacks of excruciating, lightening
like jabs of facial pain.
• A paraoxysm (sudden sharp pain) can last for
15 mins or more.
• The maxillary nerve is most frequently
involved, then the mandibular nerve, and least
frequently the ophthalmic nerve.

58. • The pain is initiated by touching a sensitive
trigger zone of the skin.
• The cause of trigeminal neuralgia is unknown ,
but some investigators believe that it can be
due to a anomalous blood vessel that
compresses the nerve.

59. Causes of Trigeminal Neuralgia

61. Wallenberg Syndrome
• Also called the lateral medullary syndrome is a
classic clinical demonstration of the anatomy of
the fifth nerve. It provides a useful summary of
essential points about the processing of sensory
information by the trigeminal nerve.
• A stroke usually affects only one side of the body.
If a stroke causes loss of sensation, the deficit will
be lateralized to the right side or the left side of
the body. The only exceptions to this rule are
certain spinal cord lesions and the medullary
syndromes .

62. • In Wallenberg syndrome, a stroke causes loss
of pain/temperature sensation from one side of
the face and the other side of the body.
• The explanation involves the anatomy of the
brainstem. In the medulla, the ascending
spinothalamic tract (which carries
pain/temperature information from the
opposite side of the body) is adjacent to the
descending spinal tract of the fifth nerve
(which carries pain/temperature information
from the same side of the face).

63. • A stroke that cuts off the blood supply to this
area destroys both tracts simultaneously.
• The result is loss of pain/temperature
sensation (but not touch/position sensation) in
a unique “checkerboard” pattern (ipsilateral
face, contralateral body) that is entirely
diagnostic.

64. Infraorbital nerve block
• For local anesthesia of the inferior part of the
face, the infraorbital nerve is infiltrated with an
anesthetic agent. The site of injection is the
infraorbital foramen.
• Careful aspiration is essential as a careless
injection may result in passage of anesthetic
fluid into the orbit causing temporary paralysis
of the extraocular muscles.

65. Inferior alveolar nerve
block
• Care should be taken during nerve block , if
the needle goes too far posteriorly, it may enter
the parotid gland and anesthetize branches of
facial nerve, producing transient unilateral
facial paralysis.

66. Nerve damage
• Nerve damage ,which occurs almost exclusively
during the removal of lower third molars has
been reported in inferior alveolar nerve and
lingual nerve , less frequently the long buccal
nerve.

67. Inferior alveolar nerve injuries :
• Damage to inferior alveolar nerve occurs primarily
because of the anatomic relationship between the 3rd
molar and nerve.
• IAN enters the mandible at the mandibular foramen
and exists the mandible at the sides of the chin from
mental foramen.

69. Injury to lingual nerve : • Lingual nerve is more suspectable to traumatic injury
in 3rd molar region because of its proximity to the retro
molar and paralingual sulcus mucosa.
• Lingual nerve courses just inside the jaw bone,
entering the tongue and supplying sense of touch and
taste to the right and left half of anterior 2/3 of tongue
as well as lingual gingiva.

70. • Injury results in abnormal taste sensation, and
visible fungiform papillae are atrophic on
lingual nerve injured sides of the anterior
tongue tip when compared with normal sides.
• Thus distrophic changes of the fungiform
papillae density of the anterior tongue tip may
provide objective assessment of LN nerve
injury in some patients.

72. Complications of LA Nerve
damage
•
LA injections may also be responsible for
nerve damage.
•
This complication can be extremely
difficult to distinguish from nerve
damage resulting from surgical
procedure itself.
•
Direct injury from needle
Epineural hematoma formation and local
toxicity from anesthetic agent.

73. • Hematoma formation within the epineurium appears
to be the most likely cause of nerve damage.
• A particular cause of nerve injury may be associated
with the use of needle that has developed a barb as a
result of contacting bone as part of normal IAN Block
procedure.

74. Clinical evaluation of CN V
• The sensory function is tested by asking the patient to
close his or her eyes and respond when feeling a
touch.
• A piece of guaze or test tubes filled with warm and
cold fluid are applied to one cheek and then to the
corresponding position on the other side. The testing
is then repeated with gentle touch of a sharp pin
alternating sides.

75. • The motor function is tested by asking the
patient to open the mouth against resistance .
Action of both pterygoid muscles keeps the
open jaw in the midline. If pterygoid muscles
of one side is paralysed , the jaw is deviated to
the paralysed side ( Pterygoid muscles of one
side pushes the jaw to the opposite side
normally ).

77. Conclusion
• The trigeminal nerve forms the most
important cranial nerve of the orofacial
region.
• The anatomy and distribution are of
importance to identify the pathology and
physiology.

78. AbducenS Nerve (CN VI)

79. • Origin : fibres originate from the ipsilateral abducens nuclei
located in the caudal pons beneath the 4th ventricle
• Component: Motor
• Function: Lateral rectus muscle turns eyeball laterally
• Opening to the Skull: Superior orbital fissure
• Supplies : Lateral rectus muscle.
 Clinical Significance of the Abducens Nerve (Lateral Gaze)
• This causes medial strabismus (the affected eye deviates
medially by the unopposed action of the medial rectus
muscle).
• The individual may be able to move the affected eye to the
midline, but no further, by relaxing the medial rectus muscle.

80. APPLIED ANATOMY OF ABDUCENS
NERVE
Medial
strabismus

81. Facial Nerve (CN VII)

82.  Component: Mixed
 Origin : Medulla oblongata
 Opening to the Skull: Internal acoustic meatus, facial canal, stylomastoid foramen
 Function:
 Motor
o muscles of the face and scalp
o Stapedius muscle
o Posterior belly of digastric
o Stylohyoid muscles
 Sensory
o Taste from ant. 2/3 of tongue, from the floor of the mouth and palate
 Secretomotor
o Submandibular and sublingual salivary glands
o Lacrimal gland
o Glands of nose and palate

84. Nuclear Origin Of Facial Nerve
•
The facial nerve fibers are connected to the following
4 cranial nuclei :
1. Motor nucleus of facial nerve – fibers supplying
muscles of second branchial arch originate here.
2. Superior salivatory nucleus – provides the
preganglionic parasympathetic secretomotor fibers.
3. Nucleus of tractus solitarius – fibers responsible for
taste sensation.
4. Spinal nucleus of trigeminal nerve – fibers for pain
and temperature sensations.

85. BRANCHES OF FACIAL NERVE
Branches within facial canal :
1. Greater petrosal nerve
2. Nerve to the stapedius
3. Chorda tympani
Branches immediately below the stylomastoid
foramen :
1. Posterior auricular
2. Diagastric
3. Stylohyoid
Branches within the parotid gland :
1. Temporal
2. Zygomatic
3. Buccal
4. Mandibular
5. Cervical

87. FUNCTION OF FACIAL
NERVES

88. APPLIED ANATOMY OF
FACIAL NERVE

89. Facial palsy
• Facial palsy is due to the paralysis of facial nerve.
• It is of 2 types – * Upper motor neuron
type
* Lower motor neuron
type
• Upper motor neuron facial palsy is due to the involvement of
corticonuclear fibers.
• It is also called as supranuclear type of palsy.
• It leads to paralysis of the contralateral lower part of face below the
palpebral fissure.

90. • The upper part of face is spared because the part of the
facial nucleus which supplies it, is innervated by
corticonuclear fibers from both the cerebral hemispheres.
•
Lower motor neuron palsy is of 2 types :
1. Nuclear paralysis - due to involvement of nucleus of
facial nerve, the motor nucleus of facial nerve is close to
the abducens nerve which is also usually affected, it
leads to paralysis of muscles of the entire face on
ipsilateral side.
2. Infranuclear paralysis : This occurs due to involvement
of facial nerve.

91. Bell’s Palsy
• Is a lower motor neuron type of facial nerve
involvement.
• It has varied etiology eg : exposure to sudden
cold, middle ear infections.
• It leads to paralysis of muscles of facial
expression.

93. Millard Gubuler Syndrome
• Abducens nerve palsy on the ipsilateral
side.
• Infra nuclear type of facial nerve palsy.
• Contra lateral hemiplegia.

94. Raymond Foville Syndrome
• Paralysis of conjugate occular deviation to
same side of lesion.
• Contralateral hemiplegia, infra nucleus
facial nerve palsy on the same side.

95. Ramsay Hunt Syndrome
• Herpetic eruption in the external acoustic
meatus due to the involvement of facial nerve.
• Facial nerve injured by forceps delivery,
fracture of skull, tumour, middle ear infection.

96. Injury of Zygomatic branch of CN
VII
• Leads to paralysis, loss of tonus of
orbicularis oculi, in the lower eyelid thus
the lower eye lid drops.
• As a result, tears do not spread over the
cornea and the dry cornea ulcerates –
results in corneal scar – impairs vision.

97. Paralysis of Buccal
branch
• It prevents the emptying of food from the
vestibule of the cheeks.
• The food lodges in the vestibule and
cannot be maintained in position between
the teeth for chewing.

98. Paralysis of Marginal
mandibular branch of CN VII
• This may occur when an incision is made
along the inferior border of the mandible.
• Injury to this branch results in an
unslightly drooping of the corner of the
mouth.

99. Injury of Facial nerve at various
sites

100. Clinical evaluation of
Facial nerve
Tested by checking the facial muscles :
1. FRONTALIS: Ask the patient to look upward
without moving his head and look for normal
horizontal wrinkles of the forehead.
2. ORBICULARIS OCULI: Tight closure of eyes.
3. ORBICULARIS ORIS: whistling and pursing
the mouth.

101. 4. DILATOR OF MOUTH: Showing the
teeth.
5. BUCCINATOR: Puffing the mouth and
then blowing forcibly.
6. PLATYSMA: Forcible pulling of the
angle of the mouth downwards and
backwards forcing vertical folds of skin
on the side of the neck.

102. • Taste on each half of the anterior two
thirds of the tongue can be tested with
sugar, salt, vinegar and quinine for sweet,
salt, sour and bitter sensation.

103. CONCLUSION
• Thus the facial nerve which supplies all
facial muscles plays an important role in
facial expression.
• Any damage or injury to the nerve affects
all the muscles of the face and leads to
paralysis.

104. Vestibulocochlear Nerve
CN (VIII)

105. • Other Names : Auditory / Acoustic Nerve
• Component : Sensory
• Function:
o Vestibular – Saculae/saccule/semicircular canals –
Balance position of head
o Cochlear – Organ of Corti – Hearing
• Origin: Medulla oblongata
• Opening to the Skull: Internal acoustic meatus

106. Vestibulocochlear Nerve

107. Vestibular Branch
•
Vestibular branch arises from the vestibular organs of
equilibrium and balance.
•
Relays afferent information related to the position and
movement of the head
•
Central processes of the vestibular nerve are located in the
vestibular ganglion, which is situated in the internal acoustic
meatus.
•
Its fibres conduct impulses to the vestibular nuclei within the
pons and medulla oblongata.
•
Fibres from there extend to the thalamus and cerebellum.

108. Cochlear Branch
• Cochlear branch arises from the Organ of
Corti in the cochlea and is concerned with
hearing.
• It conveys impulses through the spiral
ganglion to the cochlear nuclei within the
medulla oblongata.
• From there fibres extend to the thalamus and
synapse there with neurons that convey the
impulses to the auditory areas of the cerebral
cortex.

109. CLINICAL ANATOMY OF
VESTIBULOCOCHLEAR NERVE
Damage produces:
• Deafness
• Dizziness
• Nausea
• Loss of balance
• Nystagmus

110. Glossopharyngeal NERVE
CN IX

111. • Other Name : Hering ’s nerve
• Component : Mixed
• Origin: Medulla oblongata
• Opening to the Skull: Jugular foramen
•
Function:
• Motor
Stylopharyngeus muscle – assists swallowing
• Sensory
Pharynx
Carotis sinus and carotid body
Gustatory :Posterior one third of tongue including circumvallate papillae.
• Secretomotor
Parotid gland

112. Branches of Glossopharyngeal nerve
1. Communicating branch
- a twig to the ganglion of vagus nerve
- a twig to auricular branch of vagus
nerve.
2. Tympanic branch
- Lesser petrosal nerve - carry pre-ganglionic
parasympathetic secretomotor fibres to parotid
gland .
- twigs to tympanic cavity, auditory
tube

113. 3. Carotid branch – supplies the carotid sinus
4. Pharyngeal branch - form plexus with
branches of vagus and sympathetic .
5. Branch to stylopharyngeus
6. Tonsillar branches - tonsil and soft palate
7. Lingual branches - taste and general sensation
from posterior one third of tongue .

115. APPLIED ANATOMY OF
GLOSSOPHARYNGEAL NERVE

116. • Complete lesion of the glossopharyngeal nerve
results in the following :
1. Loss of taste and common sensations over the
posterior one third of the tongue.
2. Difficulty in swallowing
3. Loss of salivation from the parotid gland
4. Unilateral loss of gag reflex
•
Complete lesion of glossopharyngeal nerve is
rare in isolation. There is often involvement of
vagus nerve.

117. Glossopharyngeal Neuralgia
• It is known as tic douloureux of CN IX or
Cranial mononeuropathy IX .
• It is a condition in which there are repeated
episodes of severe pain in the tongue, throat, ear
and tonsils which can last from few seconds to
few minutes.
• It is believed to be caused by irritation of the
ninth cranial nerve.

118. • The sudden intensification of pain is of a burning or
stabbing nature.
• Paroxysms of pain are initiated by swallowing,
protruding the tongue, talking or touching the palatine
tonsil.
• Pain paroxysms occur during eating when trigger
areas are stimulated.

119. Clinical Evaluation Of
Glossopharyngeal Nerve
• Ninth nerve is tested by tickling the
posterior wall of pharynx. There is reflex
contraction of pharyngeal muscles called
gag reflex .
• In IX nerve paralysis there is no such
contraction.

120. Conclusion
• Injuries to glossopharyngeal nerve results in
absence of taste sensation on the posterior one
thirds of tongue and absence of gag reflex on the
side of lesion.
• Hence it is important to know the anatomy of
glossopharyngeal nerve as it is usually
accompanied by signs of involvement of
adjacent nerves.

121. Vagus Nerve (CN X)

123. • Vagus nerve is a mixed nerve.
• Containing approximately 80% sensory fibers.
• It supplies :
 Organs of voice and respiration with both motor
and sensory fibres .
 Pharynx (except stylopharyngeus), oesophagus,
stomach and heart with motor fibres.
 One muscle of the tongue (palatoglossus).
 The muscles of the soft palate (except tensor veli
palatini ).
• It is the most extensive cranial nerve, consisting
of many branches.

124. COURSE OF VAGUS NERVE
• The nerve runs from the lower brainstem through the
base of the skull to travel in the neck with the carotid
artery and jugular vein.
• It then penetrates the chest to travel to the heart and
lungs.
• It continues on to the abdomen where it breaks into a
network of nerves to the abdominal organs.
• Supplies motor and sensory parasympathetic fibres to
pretty much everything from the neck down to the first
third of the transverse colon.

125. • It is involved in, amongst other things, such as heart
rate, gastrointestinal peristalsis, sweating, and
speech (via the recurrent laryngeal nerve) and also
the controls a few skeletal muscle of the pharynx and
larynx:






Levator veli palatini muscle
Salpingopharyngeus muscle
Stylopharyngeus muscle
Palatoglossus muscle
Palatopharyngeus muscle
Superior, middle and inferior pharyngeal
constrictors

127. CLINICAL ANATOMY OF VAGUS
NERVE
• Lesion Of Vagus Nerve Leads To :
Dysphagia
Hoarseness
Uvula points away from the affected side
 Loss of gag and cough reflex

128. Accessory Nerve
(CN XI)

129. • Component: Motor
•
Function:

o
o
o
Cranial root
Muscles of soft palate (except tensor veli palatini)
Muscles pharynx (except styopharyngeus)
Muscles of larynx (except cricothyroid)
 Spinal root
o Sternocleidomastoid
o Trapezius muscle
• Origin: Medulla oblongata
• Opening to the Skull: Jugular foramen

130. • The sternocleidomastoid muscle turns the head
and the trapezius muscle braces the shoulder
and rotates the scapula during elevation of the
upper limbs.

131. ASSESSING X & XI CRANIAL
NERVES
• CN X &XI can be assessed together by testing the
gag reflex, palatal movement and sensation.
– Touching the pharynx with an orange stick tests pharyngeal
sensation (9th nerve) and the gag reflex (9th and 10th
nerve). On phonation the soft palate should rise
symmetrically in the midline (10th nerve).
• CN XI can be tested by assessing the power of the
sternocleidomastoid and the trapezius muscles i.e.
turning the head and shrugging the shoulders.

132. APPLIED ANATOMY OF
ACCESSARY NERVE
• Lesion may result the followings :
 Shoulder droop
 Weakness turning head to opposite side

133. Hypoglossal Nerve
(CN XII)

134. • Component : Motor.
• Supplies : Muscles of the tongue except the
palatoglossus.
• Fibers arises : From the hypoglossal Nucleus
which lies in the Medulla, in the floor of the
fourth verticle deep to hypoglossus triangle.
• Opening to the skull : Hypoglossal canal.

136. • After coming out of the cranial cavity the nerve
lies deep to the internal carotid artery and the
ninth, tenth and eleventh cranial nerves.
• Finally the nerve ends by dividing into terminal
branches.
• Some fibers of the first cervical nerve join the
hypoglossal nerve and are distributed through its
branches.

137. • After coming out of the cranial cavity the nerve
lies deep to the internal carotid artery and the
ninth, tenth and eleventh cranial nerves.
• Finally the nerve ends by dividing into terminal
branches.
• Some fibers of the first cervical nerve join the
hypoglossal nerve and are distributed through its
branches.

138. BRANCHES OF HYPOGLOSSAL
NERVE
1. Muscular branches :
These are branches of the hypoglossal nerve proper and
supply all the muscles of the tongue expect
palatoglossus which is supplied by the cranial root of
accessory nerve via the pharyngeal plexus.
1. Branches of the Hypoglossal nerve containing
C1 fibers :
* Meningeal branch – It supplies the duramater of
posterior cranial fossa.

139. * Descendens hypoglossi or upper root of ansa
cervicalis – it arises from the nerve as it crosses the
internal carotid artery. It runs downwards to join the
inferior root of ansa cervicalis.
* Nerve to thyrohyoid
3. Nerve to geniohyoid
4. Communicating branches

142. APPLIED ANATOMY OF
HYPOGLOSSAL NERVE

143. Injury to the Hypoglossal nerve
• The hypoglossal nerve
accompanies the tonsillar artery
on the laterial wall of the
pharynx and this wall is
vulnerable to injury during
tonsillectomy.
• Injury to CN twelve paralyses
the ipsilateral half of the tongue.
After some time the tongue
atrophies, making it appear
shrunken and wrinkled.

144. • When the tongue is protruded, its tip deviates
towards the paralysed side because of the
unopposed action of the genioglossus in the
normal side of the tongue.

145. Clinical Evaluation Of Hypoglossal
Nerve
• The hypoglossal nerve is
tested clinically by asking the
patient to protrude his tongue.
Normally the tongue is
protruded straight forward. If
the nerve is paralysed, the
tongue deviates to the
paralysed side.

146. Conclusion
• The Hypoglossal –the twelfth cranial
nerve which supplies all the muscles of
the tongue.
• Thus any injury to the nerve lead to
paralysis, muscles of the affected side
undergo atrophy and the movement of the
tongue is affected

147. REFERENCES
• B D Chaurasia - Textbook of Human’s Anatomy –
5th Edition
• Tortora - Principles of Anatomy and physiology12th Edition
• Keith L Moore - Clinically oriented anatomy – 6th
Edition
• Harold Ellis - Clinical anatomy - 12th Edition
• Richard S.Snell – Clinical anatomy – 8th Edition
• Julian.B.Woelfel - Dental anatomy – 6th Edition
• Inderbir Singh - Textbook of Anatomy – 8th Edition
• www.google images.com
• www.wikipedia.com