A VERY GOOD MORNING!

Dr.Priyanka shaRma1st year mdsdepartment of public health dentistryjss dental college & hospital

CRANIAL NERVEs

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

• 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

• 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

• Abducens Nerve

- Introduction

- Applied Anatomy

• Facial Nerve

- Introduction

- Nuclear Origin

- Branches

- Applied Anatomy

- Clinical Evaluation

- Conclusion

• Vestibulocochlear Nerve

- Introduction

- Branches

- Vestibular

- Cochlear

- Applied Anatomy

• Glossopharyngeal Nerve

- Introduction

- Branches

- Applied Anatomy

- Clinical Evaluation

- Conclusion

• 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

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.

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

DEVELOPMENTIn 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 73rd arch- CN 94th arch- Superior Laryngeal Branch of CN 106th arch- Recurrent Laryngeal Branch of CN 10

SENSORY/

AFFERENT

OLFACTORY

OPTIC

VESTIBULO

COCHLEAR

MOTOR/

EFFERENT

OCCULOMOTOR

TROCHLEAR

ABDUCENS

ACCESSARY

HYPOGLOSSAL

MIXTURE

TRIGEMINAL

FACIAL

VAGUS

GLOSSO

PHARYNGEAL

OLFACTORY NERVE (CN1)

OLFACTORY PATHWAY

1st neuron

•Bipolar neurons – Olfactory Cells

•Olfactory Nerves

2nd Neuron

•Mitral & tufted cells in the Olfactory bulb fibers form OLFACTORY TRACT Lateral & Medial Olfactory Striae

3rd Neuron

•Located in Primary Olfactory Cortex (Piriform lobe & Septal Nucleus)

•Anterior Perforated substances & small masses of grey matter

4th Neuron

•Secondary olfactory cortex

•Located anterior to the parahippocampal gyrus

CLINICAL ANATOMY

Anosmia

-Loss of smell Cerebrospinal fluid rhinorrhoea Temporal lobe epilepsy Kluver Bucy Syndrome

OPTIC NERVE (CN2)

Bipollar cells

Optic nerve

Optic Canal

Optic Chiasma

Optic Tract

Lateral Geniculate nucleus

Primary Visual cortex of Occipital Lobe

VISUAL PATHWAY

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

Oculomotor Nerve (CN III)

• 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” .

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.

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 non-functional and the dilator pupillae is unopposed;

• Inability for the affected eye to focus on near objects as the ciliary muscles have also been paralysed.

MYDRIASIS DIPLOPIA

PTOSIS EXOTROPIA

Trochlear Nerve (CN IV)

• 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.

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.

 

DIPLOPIA

BIELSCHOWSKY'S PHENOMENA

Trigeminal Nerve (CN V)

• 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 FaceMotor 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.

• 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.

Trigeminal Ganglion

• 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.

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.

Trigeminal Nerve – Nuclear Origin

There are 4 trigeminal nuclei .One motor and three sensory nuclei.

• 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.

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

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

OphthalmicDivision (VI)

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

COURSE OF MAXILLARY NERVEPterygopalatine Fossa

Lateralward On The Back Of The Maxilla

It Traverses The Infraorbital Groove And Canal

Appears Upon The Face At The InfraorbitalForamen

Enters The Orbit Through The Inferior Orbital Fissure

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.

• 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.

• 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.

• 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.

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.

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.

BRANCHES OF MANDIBULAR NERVE

Mental Foramen

innervates the mucosa of the mouth and gums.

innervates the external auditory meatus and portions of the external surface of the tympanic membrane.

provides general sensation to the anterior 2/3 of the tongue

innervate the lower teeth and gums. chin and lower lip

nerve to the masseter m , temporalis m., medial and lateral pterygoids, tensor palati and tensor tympani.

anterior belly of the digastric muscle.

V3

Sensory Branches of Mandibular Division (V3)

Sensory Branches of Mandibular Division (V3) cont:

Buccal

Auriculotemporal

Lingual n.Mental

Inf. alvolar

Mandibular (V3)

Motor Branch of Mandibular Nerve (V3)

Suparhyoid MusclesMylohyoid Anterior Belly Of

Digastric

Muscle ChewingMasseterTemporalis Medial & Lateral

Pterygoid

Tensor Palati

Tensor Tympani

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 Labial – Infraorbital & Ant sup Alv nerve

Ant sup alveolar nerve

Nasopalatine nerve

Premolars Middle sup alv nerve

Palatal – Ant palatine nerveBuccal – 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 nerveBuccal – Post sup alveolar nerve

Post sup alveolar nerve

Ant palatine nerveSoft palate – Middle and post palatine nerves

Mandibular arch

Anteriors Incisive branch of Inferior alv nerve

Lingual – Lingual NLabial – Mental N

Incisive N Lingual N

Premolars Dental branch of Inferior alv nerve

Lingual – Lingual NBuccal – Mental N

Dental branch of inferior alveolar nerve

Lingual nerve

Molars Dental branch of inferior alveolar nerve

Lingual – Lingual NBuccal – Buccinator N

Dental branch of inferior alveolar nerve

Lingual nerve

TEETH DENTAL PULP

GINGIVA PDL & ALV.PRO

LINGUAL SIDE

APPLIED ANATOMY OF TRIGEMINAL NERVE

• 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.

Trigeminal Neuralgia

• 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.

Causes of Trigeminal Neuralgia

• 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 .

Wallenberg Syndrome

• 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).

• 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.

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.

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.

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.

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.

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.

• 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.

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.

• 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.

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.

• 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 ).

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.

AbducenS Nerve (CN VI)

• 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.

APPLIED ANATOMY OF ABDUCENS NERVE

Medial strabismus

Facial Nerve (CN VII)

Component: Mixed Origin : Medulla oblongata Opening to the Skull: Internal acoustic meatus, facial canal, stylomastoid foramen

Function: Motor

o muscles of the face and scalpo Stapedius muscleo Posterior belly of digastrico Stylohyoid muscles

Sensoryo Taste from ant. 2/3 of tongue, from the floor of the mouth and palate

Secretomotoro Submandibular and sublingual salivary glandso Lacrimal glando Glands of nose and palate

• 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.

Nuclear Origin 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 :

4. Posterior auricular

5. Diagastric

6. Stylohyoid

Branches within the parotid gland :

7. Temporal

8. Zygomatic

9. Buccal

10. Mandibular

11. Cervical

BRANCHES OF FACIAL NERVE

FUNCTION OF FACIAL NERVES

APPLIED ANATOMY OF

FACIAL NERVE

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.

• 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.

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.

Millard Gubuler Syndrome

• Abducens nerve palsy on the ipsilateral side.

• Infra nuclear type of facial nerve palsy.

• Contra lateral hemiplegia.

Raymond Foville Syndrome

• Paralysis of conjugate occular deviation to same side of lesion.

• Contralateral hemiplegia, infra nucleus facial nerve palsy on the same side.

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.

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.

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.

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.

Injury of Facial nerve at various sites

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.

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.

• 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.

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.

Vestibulocochlear Nerve CN (VIII)

• Other Names : Auditory / Acoustic Nerve

• Component : Sensory

• Function: o Vestibular – Saculae/saccule/semicircular canals –

Balance position of heado Cochlear – Organ of Corti – Hearing

• Origin: Medulla oblongata

• Opening to the Skull: Internal acoustic meatus

Vestibulocochlear Nerve

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.

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.

CLINICAL ANATOMY OF VESTIBULOCOCHLEAR NERVE

Damage produces:• Deafness• Dizziness • Nausea• Loss of balance • Nystagmus

Glossopharyngeal NERVE CN IX

• 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

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

Branches of Glossopharyngeal nerve

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 .

APPLIED ANATOMY OF GLOSSOPHARYNGEAL

NERVE

• 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.

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.

• 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.

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.

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.

Vagus Nerve (CN X)

• 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.

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.

• 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

CLINICAL ANATOMY OF VAGUS NERVE

• Lesion Of Vagus Nerve Leads To :

DysphagiaHoarsenessUvula points away from the affected side Loss of gag and cough reflex

Accessory Nerve (CN XI)

• Component: Motor

• Function:

Cranial root o Muscles of soft palate (except tensor veli palatini)o Muscles pharynx (except styopharyngeus)o Muscles of larynx (except cricothyroid)

Spinal root o Sternocleidomastoid o Trapezius muscle

• Origin: Medulla oblongata

• Opening to the Skull: Jugular foramen

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

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.

APPLIED ANATOMY OF ACCESSARY NERVE

• Lesion may result the followings :

Shoulder droop

Weakness turning head to opposite side

Hypoglossal Nerve (CN XII)

• 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.

• 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.

• 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.

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.

2. Branches of the Hypoglossal nerve containing

C1 fibers :

* Meningeal branch – It supplies the duramater of posterior cranial fossa.

* 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

APPLIED ANATOMY OF HYPOGLOSSAL NERVE

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.

• 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.

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.

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

REFERENCES• B D Chaurasia - Textbook of Human’s Anatomy – 5th

Edition• Tortora - Principles of Anatomy and physiology-12th

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

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