DR.CHAITHRASHREE

3. CONTENTS
Ⅵ Abducent nerve
Ⅶ Facial nerve
Ⅷ Vestibulocochlear nerve
Ⅸ Glossopharyngeal nerve
Ⅹ Vagus nerve
Ⅺ Accessory nerve
Ⅻ Hypoglossal nerve
• Cervical plexus
• Conclusion
• References

5. Contents
Cranial nerves
 Ⅰ Olfactory nerve
 Ⅱ Optic nerve
 Ⅲ Occulomotor nerve
 Ⅳ Trochlear nerve
 Ⅴ Trigeminal nerve
 Ⅵ Abducent nerve
 Ⅶ Facial nerve
 Ⅷ Vestibulocochlear nerve
 Ⅸ Glossopharyngeal nerve
 Ⅹ Vagus nerve
 Ⅺ Accessory nerve
 Ⅻ Hypoglossal nerve

6. Abducens Nerve (CN VI)
• The abducens nerve is the sixth paired
cranial nerve.
• It is purely motor.
• Function
– providing innervation to the lateral
rectus muscle.

8. The abducens nerve arises from the abducens nucleus in the pons of the
brainstem. It exits the brainstem at the junction of the pons and the medulla.
It then enters the subarachnoid space and pierces the dura mater
to travel in an area known as Dorello’s canal.
At the tip of petrous temporal bone, the abducens nerve leaves Dorello’s canal
and enters the cavernous sinus (a dural venous sinus). It travels through the
cavernous sinus and enters the bony orbit via the superior orbital fissure.
Within the bony orbit, the abducens nerve terminates by
innervating the lateral rectus muscle.

9. Motor Function
• The abducens nerve provides
innervation to the lateral rectus muscle
– one of the extraocular muscles.
• It acts to abduct the eyeball (i.e. to
rotate the gaze away from the midline).

10. Clinical Relevance – Examination of the
Abducens Nerve
• The abducens nerve is examined in
conjunction with the oculomotor and
trochlear nerves by testing the
movements of the eye.
• The patient is asked to follow a point
with their eyes (commonly the tip of a
pen) without moving their head. The
target is moved in an ‘H-shape’ and the
patient is asked to report any blurring of
vision or diplopia (double vision).

11. Clinical Relevance – Abducens Nerve Palsy
• Abducens nerve palsy can be caused by any structural pathology
which leads to downwards pressure on the brainstem
(e.g. space-occupying lesion). This can stretch the nerve from its origin
at the junction of the pons and medulla.
• Other causes include diabetic neuropathy and thrombophlebitis of the
cavernous sinus.
• The abducent nerve sometimes involved in fracture of cranial nerve this
result in paralysis of cranial nerve leads to diplopia
• Clinical features of abducens nerve palsy include :
Diplopia, the affected eye resting in adduction (due to unopposed
activity of the medial rectus), and inability to abduct the eye.
 The patient may attempt to compensate by rotating their head to allow
the eye to look sideways.

12. The Facial Nerve (CN VII)

13. The Facial Nerve (CN VII)
• The facial nerve, CN VII, is the seventh paired cranial nerve.
• The facial nerve is associated with the derivatives of the second pharyngeal arch.
• Motor:
 Innervates the muscles of facial expression,
 the posterior belly of the digastric,
 the stylohyoid and the stapedius muscles.
• Sensory:
 A small area around the concha of the auricle.
• Special Sensory:
Provides special taste sensation to the anterior 2/3 of the tongue.

14. • Parasympathetic:
• Supplies many of the glands of the
head and neck, including:
Submandibular and sublingual
salivary glands.
Nasal, palatine and pharyngeal
mucous glands.
Lacrimal glands.

15. Nucleui of origin
• Motor nucleus of facial nerve : it lies near the lower
part of pons.
• Superior salivatory nucleus :It lies in the pons lateral
to the main motor nucleus gives rise to secretomotor
parasympathetic fibers
• Nucleus solitarus : It lies in the medulla , receives the
taste sensation
• GSA fibers : fibers from back of auricle through
communication from auricular branch of vagus these
fibers terminate in main sensory nucleus of 5th nerve.

16. Cervical

17. Anatomical Course
• The course of the facial nerve is very complex. There are many branches, which
transmit a combination of sensory, motor and parasympathetic fibres.
• Anatomically, the course of the facial nerve can be divided into two parts:
Intra cranial – the course of the nerve through the cranial cavity, and the cranium
itself.
Extra cranial – the course of the nerve outside the cranium, through the face and
neck.

19. The nerve arises in the pons, an area of the brainstem. It begins as two
roots; a large motor root, and a small sensory root
The two roots travel through the internal acoustic meatus,
a 1cm long opening in the petrous part of the temporal
bone. Here, they are in very close proximity to the inner ear.
Still within the temporal bone, the roots leave the internal acoustic meatus, and
enter into the facial canal. The canal is a ‘Z’ shaped structure.
INTRCRANIAL

21. Within the facial canal, three important events occur:
Firstly the two roots fuse to form the facial nerve
Next, the nerve forms the geniculate ganglion (a ganglion is a collection of nerve cell bodies).
Lastly, the nerve gives rise to:
The facial nerve then exits the facial canal (and the cranium) via the stylomastoid
foramen. This is an exit located just posterior to the styloid process of the temporal bone.
Greater petrosal nerve – parasympathetic fibres to mucous glands and lacrimal gland.
Nerve to stapedius – motor fibres to stapedius muscle of the middle ear.
Chorda tympani – special sensory fibres to the anterior 2/3 tongue and parasympathetic fibres to the
submandibular and sublingual glands.

22. After exiting the skull, the facial nerve turns superiorly to run just
anterior to the outer ear.
The first extra cranial branch to arise is the posterior auricular
nerve . It provides motor innervation to the some of the muscles
around the ear.
Immediately distal to this, motor branches are sent to the
posterior belly of the digastric muscle and to the stylohyoid
muscle
The main trunk of the nerve, now termed the motor root of the facial
nerve, continues anteriorly and inferiorly into the parotid gland
Within the parotid gland, the nerve terminates by splitting into
five branches:
These branches are responsible for innervating the muscles of
facial expression.
Temporal branch , Zygomatic branch , Buccal branch , Marginal
mandibular branch , Cervical branch
EXTRA CRANIAL

24. Motor Functions
• Branches of the facial nerve are responsible for innervating many of the muscles of the head and neck.
• All these muscles are derivatives of the second pharyngeal arch.
• The first motor branch arises within the facial canal;
the Nerve to stapedius-The nerve passes through the pyramidal eminence to supply the stapedius
muscle in the middle ear.
• Between the stylomastoid foramen, and the parotid gland, three more motor branches are given off:
Posterior auricular nerve – Ascends in front of the mastoid process, and innervates the intrinsic
and extrinsic muscles of the outer ear. It also supplies the occipital part of the occipitofrontalis
muscle.
Nerve to the posterior belly of the digastric muscle – Innervates the posterior belly of the
digastric muscle (a suprahyoid muscle of the neck). It is responsible for raising the hyoid bone.
Nerve to the stylohyoid muscle – Innervates the stylohyoid muscle (a suprahyoid muscle of the
neck). It is responsible for raising the hyoid bone.

25. • Within the parotid gland, the facial nerve
terminates by bifurcating into five motor
branches. These innervate the muscles of facial
expression:
• Temporal branch – Innervates the frontalis,
orbicularis oculi and corrugator supercilii
• Zygomatic branch – Innervates the orbicularis
oculi.
• Buccal branch – Innervates the orbicularis
oris, buccinator and zygomaticus muscles.
• Marginal Mandibular branch – Innervates
the mentalis muscle.
• Cervical branch – Innervates the platysma.

26. Special Sensory Functions
• The chorda tympani branch of the facial nerve is responsible for innervating the
anterior 2/3 of the tongue with the special sense of taste.
• The nerve arises in the facial canal, and travels across the bones of the middle ear,
exiting via the petrotympanic fissure, and entering the infratemporal fossa.
• Here, the chorda tympani ‘hitchhikes’ with the lingual nerve.
• The parasympathetic fibres of the chorda tympani stay with the lingual nerve, but the
main body of the nerve leaves to innervate the anterior 2/3 of the tongue.

27. PARASYMPATHETIC FUNCTION
• The parasympathetic fibres of the facial nerve are carried by the greater
petrosal and chorda tympani branches.
• Greater Petrosal Nerve
The greater petrosal nerve arises immediately distal to the geniculate
ganglion within the facial canal. It then moves in anteromedial direction, exiting
the temporal bone into the middle cranial fossa. From here, its travels across (but
not through) the foramen lacerum, combining with the deep petrosal nerve to
form the nerve of the pterygoid canal.
The nerve of pterygoid canal then passes through the pterygoid canal (Vidian
canal) to enter the pterygopalatine fossa, and synapses with the pterygopalatine
ganglion. Branches from this ganglion then go on to provide parasympathetic
innervation to the mucous glands of the oral cavity, nose and pharynx, and
the lacrimal gland.

28. • Chorda Tympani
• The chorda tympani also carries some parasympathetic fibres.
• These combine with the lingual nerve (a branch of the trigeminal nerve) in
the infratemporal fossa and form the submandibular ganglion.
• Branches from this ganglion travel to the submandibular and
sublingual salivary glands.

29. Ganglion associated with facial nerve
• Geniculate ganglion
• Submandibular ganglion
• Pterygopalatine ganglion
• Geniculate ganglion : Geniculate ganglion is L shaped collection of fibers
& sensory neurons of the facial nerve
• It receives fibers from motor , sensory , & parasympathetic components of facial
nerve & send fibers that will innervate lacrimal , submandibular, sublingual,
tongue ,palate, pharynx external auditory meatus , stapedius, posterior belly of
digastric & muscles of facial expression

31. Submandibular ganglion
• Submandibular ganglion is small and
fusiform shape it is situated above and
deep portion of the submandibular gland
• Ganglion hangs by 2 nerve filaments it is
suspended by lingual nerve in 2
filaments one anterior & one posterior .
Through the posterior of these receives a
branch from CHORDA TYMPANI

32. Pterygopalatine ganglion
• The pterygopalatine ganglion is a
parasympathetic ganglion found in the
pterygopalatine fossa
• Its largely innervated by greater petrosal
nerve & its axon project into lacrimal
gland & nasal mucosa

33. Testing of facial nerve
• Purpose of the test
• To detect any unilateral or bilateral weakness of facial muscles (UMN or
LMN)
• Detect impairment of taste
• Method of testing :
• Observation
• Symmetry and asymmetry of face
• Nasolabial fold & wrinkle on forehead

34. Testing the temporal branch of facial nerve :
patient is asked to frown & wrinkle his or her forehead
Testing zygomatic branch of facial nerve :
patient is asked to close their eyes tightly
Testing the buccal branch :
puff up cheeks , smile & show teeth
The marginal mandibular branch
may be injured during surgery in the neck region during exicision of
salivary gland

35. • Examination of taste
• The four primary taste (sweet, salt, sour, bitter) can be carried out by using sugar,
salt, vinegar & quinine
• The side of the tongue is moistened by the test substance
• Ask the Pt to indicate taste by pointing
• Secretomotor function
• The flow of tears of two side can be compared by giving ammonia to inhale which
will result in tearing of eye
• The flow of saliva can be tasted by keeping a spicy substance in the tongue & the
tip is raised to observe the sub maxillary salivary flow

36. • Reflexes
• Corneal reflex
• Nasopalpebral reflex: tap on the nasopalpebral ridge will produce closure of
both eyes. In bells palsy there is failure to close on the affected side

37. Clinical Relevance: Damage to the Facial
Nerve
• The facial nerve has a wide range of functions. Thus, damage to the nerve can produce a
varied set of symptoms, depending on the site of the lesion.
• Intracranial Lesions
• Intracranial lesions occur during the intracranial course of the facial nerve (proximal to the
stylomastoid foramen)
• The muscles of facial expression will be paralysed or severely weakened. The other
symptoms produced depend on the location of the lesion, and the branches that are
affected
 Chorda tympani – reduced salivation and loss of taste on the ipsilateral 2/3 of
the tongue.
 Nerve to stapedius – ipsilateral hyperacusis (hypersensitive to sound).
 Greater petrosal nerve – ipsilateral reduced lacrimal fluid production.

38. The most common cause of an
intracranial lesion of the facial nerve
is middle ear pathology – such as a
tumour or infection.
If no definitive cause can be found
then the disease is termed Bell’s
palsy.

39. • Extracranial lesions occur during the extracranial course of the facial nerve
• Only the motor function of the facial nerve is affected, therefore resulting in paralysis
or severe weakness of the muscles of facial expression.
• There are various causes of extracranial lesions of the facial nerve:
Parotid gland pathology – e.g a tumour, parotitis, surgery.
Infection of the nerve – particularly by the herpes virus.
Compression during forceps delivery – the neonatal mastoid process is not fully
developed, and does not provide complete protection of the nerve.
Idiopathic – If no definitive cause can be found then the disease is termed Bell’s
palsy.

40. DIFFERENTIATING FEATURES OF UPPER AND LOWER MOTOR LESIONS

43. Complications of parotid surgery
• Intraoperative complication : parotid
gland surgery comprises transection of
the facial nerve
• The surgeon has to immediately
recognize and management must be
performed without delay
• Immediate nerve repair is mandatory
• Postoperative complication : facial nerve
dysfunction some or all branches of
nerve is a early complication of parotid
gland surgery

44. BELL’S PALSY
First described more than a century ago by SIR CHARLES BELL
Bells palsy is most common cause of facial paralysis
 Background of bells palsy
ETIOLOGY
 The cause is often not clear.
 A type of herpes infection called herpes zoster (herpes zoster) is a
painful, blistering skin rash due to the varicella-zoster virus, the virus
that causes chickenpox might be involved.
 Other conditions that may cause Bells palsy include:
 HIV infection
 Lyme disease
 Middle ear infection
 Sarcoidosis

45. • PATHOPHSIOLOGY
• Cause by herpes virus type 1 & herpes zoster inflammation of nerve
initialy results in reversible neuropraxia
• Bells phenomenon : is the upward diversion of the eye ball on
attempted closure of the lid is seen when eye closure is incomplete

46. Features of bell’s palsy
• Unilateral involvement.
• Inability to smile , close eye or raise eyebrow.
• Unable to whistle.
• Drooping of corner of mouth.
• Inability to close eye (bell’s sign)
• Inability to wrinkle forehead.
• Loss of blinking reflex.
• Slurred speech.
• Mask like appearance of face.
• Loss / alteration of taste.

47. Diagnosis :
Paralysis of all muscles group of one side of the face
sudden onset.
Management :
Eye care : protecting the cornea from drying & abrasion due
to problems with eye lid closure
--lubricating drops should be applied
Medical treatment :
prednisolone 1mg /kg/day
corticosteroids combine with antiviral drug is better
acyclovir 400mg , 5 times /day
surgical treatment : facial nerve decompression

48. A TUMOR COMPRESSING THE FACIAL NERVE
RESULT IN FACIAL PARALYSIS

49. CONGENITAL FACIAL NERVE PALSY
Moebius syndrome (congenital )
• Abnormal 6th , 7th , 9th nerve nuclei.
• Facial nerve absent / smaller
• Congenital extra ocular muscle & facial palsy.

50. Vestibulocochlear Nerve (CN VIII)
• The vestibulocochlear nerve is the
eighth paired cranial nerve.
• It is comprised of two parts –
vestibular fibres and cochlear fibres.
• Both have a purely sensory function.

51. • The vestibular and cochlear portions of the vestibulocochlear nerve are functionally
discrete, and so originate from different nuclei in the brain:
Vestibular component – arises from the vestibular nuclei complex in the pons and
medulla.
Cochlear component – arises from the ventral and dorsal cochlear nuclei,
situated in the inferior cerebellar peduncle.
Both sets of fibres combine in the pons to form the vestibulocochlear nerve. The nerve emerges from the brain at
the cerebellopontine angle and exits the cranium via the internal acoustic meatus of the temporal bone.
Within the distal aspect of the internal acoustic meatus, the vestibulocochlear nerve splits, forming the vestibular
nerve and the cochlear nerve.
The vestibular nerve innervates the vestibular system of the inner ear, which is responsible for detecting balance.
The cochlear nerve travels to cochlea of the inner ear, forming the spiral ganglia which serve the sense of hearing.

52. Special Sensory Functions
• The vestibulocochlear nerve is unusual in that it primarily consists of bipolar neurones.
It is responsible for the special senses of hearing (via the cochlear nerve),
and balance(via the vestibular nerve).
• Hearing
• The cochlea detects the magnitude and frequency of sound waves. The inner hair
cells of the organ of Corti activate ion channels in response to vibrations of
the basilar membrane. Action potentials travel from the spiral ganglia, which house
the cell bodies of neurones of the cochlear nerve.
• The magnitude of the sound determines how much the membrane vibrates and
thereby how often action potentials are triggered. Louder sounds cause the basilar
membrane to vibrate more, resulting in action potentials being transmitted from the
spiral ganglia more often, and vice versa.

53. • Equilibrium (Balance)
• The vestibular apparatus senses changes in the position of the head in relation
to gravity.
• The vestibular hair cells are located in the otolith organs
(the utricule and saccule), where they detect linear movements of the head, as
well as in the three semicircular canals, where they detect rotational
movements of the head.
• The cell bodies of the vestibular nerve are located in the vestibular
ganglion which is housed in the outer part of the internal acoustic meatus.

54. The vestibulo-ocular reflex (also called the oculocephalic reflex) allows images on
the retina to be stabilised when the head is turning by moving the eyes in the
opposite direction.
It can be demonstrated by holding one finger still at a comfortable distance in front
of you and twisting your head from side to side whilst staying focused on the finger.

55. • Purpose of the test
• To determine any deafness is bilateral or unilateral
• Whether deafness is due disease of middle ear or cochlear nerve
• To determine the disturbance of vestibular functions
• Test of hearing
• Observe if the patient turns one ear towards you
• Evaluate hearing using a ticking watch, rub fingers together, whisper.
• Rinne’s test
• Strike a tuning fork gently, hold it near one external meatus & ask the Pt if he
can hear it
• Place it on the mastoid, ask if he can still hear it & instruct him to say “NOW”
when sound ceases, & keep it on the external meatus again (normally the note
is still audible)

56. • Weber’s test
• The fork is place on the vertex
• Ask the Pt if he can hear the sound all over
the head, in both ears or in one ear
• In nerve deafness the sound appear to be
heard on the normal ear
• Interpretation
• In middle ear deafness – the note is not
heard
• In nerve deafness – air & bone conduction
are reduced but air remains better

57. • Test of vestibular function
• Observe equilibrium as patient walks or stands
• Observe abnormal eye movements.
• Ask for
• Dizziness
• Falling
• Nausea and vomiting

58. Clinical Relevance:
Basilar Skull Fracture
• A basilar skull fracture is a fracture of the skull base, usually resulting from major
trauma.
• The vestibulocochlear nerve can be damaged within the internal acoustic meatus,
producing symptoms of vestibular and cochlear nerve damage.
• Patients may also exhibit signs related to the other cranial nerves, bleeding from the ears
and nose, and cerebrospinal fluid leaking from the ears (CSF otorrhoea) and nose (CSF
rhinorrhoea).
• Labyrinthitis refers to inflammation of the membranous labyrinth, resulting in damage to
the vestibular & cochlear branches of the vestibulocochlear nerve.
• The symptoms are similar to vestibular neuritis, but also include indicators of cochlear nerve
damage:
• Sensorineural hearing loss.
• Tinnitus – a false ringing or buzzing sound
Labyrinthitis

59. Vestibular Neuritis
• Vestibular neuritis refers to inflammation of the vestibular branch of the vestibulocochlear
nerve.
• The aetiology of this condition is not fully understood, but some cases are thought to be due
to reactivation of the herpes simplex virus.
• It presents with symptoms of vestibular nerve damage:
Vertigo – a false sensation that oneself or the surroundings are spinning or moving.
Nystagmus – a repetitive, involuntary to-and-fro oscillation of the eyes.
Loss of equilibrium (especially in low light).
Nausea and vomiting.
• The condition is usually self-resolving. Treatment is symptomatic, usually in the form of
anti-emetics or vestibular suppressants

60. • The glossopharyngeal nerve, CN IX, is the ninth paired cranial nerve.
Embryologically , the glossopharyngeal nerve is associated with the derivatives
of the third pharyngeal arch.
Sensory: Innervates the oropharynx, carotid body and sinus, posterior 1/3 of the
tongue, middle ear cavity and Eustachian tube.
Special Sensory: Provides taste sensation to the posterior 1/3 of the tongue.
Parasympathetic: Provides parasympathetic innervation to the parotid gland.
Motor: Innervates the stylopharyngeus muscle of the pharynx.
Glossopharyngeal Nerve (CN IX)

62. The glossopharyngeal nerve originates in the medulla oblongata of the brain
It emerges from the anterior aspect of the medulla, moving laterally in the posterior cranial fossa.
The nerve leaves the cranium via the jugular foramen.
At this point, the tympanic nerve arises. (It has a mixed sensory and parasympathetic composition.)
Immediately outside the jugular foramen lie two ganglia (collections of nerve cell bodies).
They are known as the superior and inferior (or petrous) ganglia – they contain the cell bodies of the sensory
fibres in the glossopharyngeal nerve.
Now extracranially , the glossopharyngeal nerve descends down the neck, anterolateral to the internal carotid
artery.
At the inferior margin of the stylopharyngeus, several branches arise to provide motor innervation to the muscle.
It also gives rise to the carotid sinus nerve, which provides sensation to the carotid sinus and body.
The nerve enters the pharynx by passing between the superior and middle pharyngeal constrictors.
Within the pharynx, it terminates by dividing into several branches – lingual, tonsil and pharyngeal.
COURSE

63. Sensory Functions
• The tympanic nerve arises as the nerve traverses the jugular foramen. It
penetrates the temporal bone and enters the cavity of the middle ear. Here, it forms
the tympanic plexus – a network of nerves that provide sensory innervation to
the middle ear, internal surface of the tympanic membrane and Eustachian
tube.
• At the level of the stylopharyngeus, the carotid sinus nerve arises. It descends
down the neck to innervate both the carotid sinus and carotid body, which
provide information about blood pressure and oxygen saturation respectively.
• The glossopharyngeal nerve terminates by splitting into several sensory branches:
Pharyngeal branch – combines with fibres of the vagus nerve to form the pharyngeal plexus.
It innervates the mucosa of the oropharynx.
Lingual branch – provides the posterior 1/3 of the tongue with general and taste sensation
Tonsillar branch – forms a network of nerves, known as the tonsillar plexus, which
innervates the palatine tonsils.

64. • Special Sensory
• The glossopharyngeal nerve provides taste sensation to the posterior 1/3 of
the tongue, via its lingual branch (Note: not to be confused with the lingual
nerve).
• Motor Functions
• The stylopharyngeus muscle of the pharynx is innervated by the
glossopharyngeal nerve.
• This muscle acts to shorten and widen the pharynx, and elevate the larynx
during swallowing.

65. • The glossopharyngeal nerve provides parasympathetic
innervation to the parotid gland.
• These fibres originate in the inferior salivatory nucleus of CN
IX. These fibres travel with the tympanic nerve to the middle
ear. From the ear, the fibres continue as the lesser petrosal
nerve, before synapsing at the otic ganglion.
• The fibres then hitchhike on the auriculotemporal nerve to
the parotid gland, where they have a secretomotor effect.
• Remember – although the facial nerve splits into its five terminal
branches in the parotid gland, it is the glossopharyngeal nerve
that actually supplies the gland.
Parasympathetic Functions

66. • Clinical Relevance – Gag Reflex
• The glossopharyngeal nerve supplies sensory innervation to the oropharynx, and
thus carries the afferent information for the gag reflex. When a foreign object
touches the back of the mouth, this stimulates CNIX, beginning the reflex. The
efferent nerve in this process is the vagus nerve, CNX.
• An absent gag reflex signifies damage to the glossopharyngeal nerve.

67. CLINICAL SIGNIFICANCE
Glossopharyngeal Neuralgia

68. M
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69. The Vagus Nerve (CN X)
• The vagus nerve is the 10th cranial nerve
(CN X).
• It is associated with the derivatives of the
fourth and sixth pharyngeal arches.
• It’s a mixed nerve, i.e., composed of both the
motor and sensory fibres but mostly it is
motor.
• Its area of distribution goes past the head and
neck-to the thorax and abdomen.
• It’s the longest and most widely distributed
cranial nerve.
• It’s so called due to its wide-ranging obscure
course and distribution. It’s a vagrant or
wandering nerve.

70. • Overview
• Sensory: Innervates the skin of the external acoustic meatus and the internal
surfaces of the laryngopharynx and larynx.
Provides visceral sensation to the heart and abdominal viscera.
• Special Sensory: Provides taste sensation to the epiglottis and root of the tongue.
• Motor: Provides motor innervation to the majority of the muscles of the pharynx,
soft palate and larynx.
• Parasympathetic: Innervates the smooth muscle of the trachea, bronchi and
gastro-intestinal tract and regulates heart rhythm.

71. Anatomical Course
• The vagus nerve has the longest course of all the cranial nerves, extending from the head to
the abdomen. Its name is derived from the Latin ‘vagary’– meaning wandering. It is
sometimes referred to as the wandering nerve.
In the Head
Auricular branch
In the Neck
 Right vagus nere
 Left vagus nerve
 Pharyngeal branch
 Superior laryngeal
nerve
 Right Recurrent
laryngeal nerve
In the Thorax
 Left recurrent
laryngeal nerve
 Cardiac
branches
In the
Abdomen
Terminal
branches

72. • In the Head
• The vagus nerve originates from the
medulla of the brainstem. It exits
the cranium via the jugular
foramen, with the
glossopharyngeal and accessory
nerves (CN IX and XI
respectively).
• Within the cranium, the auricular
branch arises. This supplies
sensation to the posterior part of the
external auditory canal and external
ear.

73. • In the Neck
In the neck, the vagus nerve passes into the carotid sheath, travelling inferiorly with the
internal jugular vein and common carotid artery. At the base of the neck, the right and
left nerves have differing pathways:
 The right vagus nerve passes anterior to the subclavian artery and posterior to the
sternoclavicular joint, entering the thorax.
 The left vagus nerve passes inferiorly between the left common carotid and left
subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.

74. • Several branches arise in the neck:
• Pharyngeal branches –
• Provides motor innervation to the majority of the muscles of the pharynx and
soft palate.
• Superior laryngeal nerve –
• Splits into internal and external branches.
• The external laryngeal nerve innervates the cricothyroid muscle of the larynx.
• The internal laryngeal provides sensory innervation to the laryngopharynx
and superior part of the larynx.
• Recurrent laryngeal nerve (right side only) –
• Hooks underneath the right subclavian artery, then ascends towards to the
larynx.
• It innervates the majority of the intrinsic muscles of the larynx.

75. In the Thorax
• In the thorax, the right vagus nerve forms the posterior vagal trunk, and the left
forms the anterior vagal trunk.
• Branches from the vagal trunks contribute to the formation of the oesophageal
plexus, which innervates the smooth muscle of the oesophagus.
• Two other branches arise in the thorax:
• Left recurrent laryngeal nerve –
• it hooks under the arch of the aorta, ascending to innervate the majority of
the intrinsic muscles of the larynx.
• Cardiac branches –
• these innervate regulate heart rate and provide visceral sensation to the
organ.
• The vagal trunks enter the abdomen via the oesophageal hiatus, an opening
in the diaphragm.

76. • In the Abdomen
• In the abdomen, the vagal trunks terminate by dividing into branches that
supply the oesophagus, stomach and the small and large bowel (up to the
splenic flexure).
•Special Sensory Functions
• The vagus nerve has a minor role in taste sensation. It carries afferent fibres from
the root of the tongue and epiglottis.

77. Sensory Functions
• There are somatic and visceral components to the sensory function of the vagus
nerve.
• Somatic refers to sensation from the skin and muscles.
• This is provided by the auricular nerve, which innervates the skin of
the posterior part of the external auditory canal and external ear.
• Viscera sensation is that from the organs of the body. The vagus nerve innervates:
• Laryngopharynx – via the internal laryngeal nerve.
• Superior aspect of larynx (above vocal folds) – via the internal laryngeal nerve.
• Heart – via cardiac branches of the vagus nerve.
• Gastro-intestinal tract (up to the splenic flexure) – via the terminal branches of
the vagus nerve.

78. Motor Functions
• The vagus nerve innervates the majority of the muscles associated
with the pharynx and larynx. These muscles are responsible for the
initiation of swallowing and phonation.
• Pharynx
Most of the muscles of the pharynx are innervated by the pharyngeal
branches of the vagus nerve:
Superior, middle and inferior pharyngeal constrictor muscles
Palatopharyngeus
Salpingopharyngeus
An additional muscle of the pharynx, the stylopharyngeus, is innervated by
the glossopharyngeal nerve.

79. • Larynx
Innervation to the intrinsic muscles of the larynx is achieved via the recurrent
laryngeal nerve and external branch of the superior laryngeal nerve.
• Recurrent laryngeal nerve:
Thyro-arytenoid
Posterior crico-arytenoid
Lateral crico-arytenoid
Transverse and oblique arytenoids
Vocalis
• External laryngeal nerve:
Cricothyroid
• Other Muscles
In addition to the pharynx and larynx, the vagus nerve also innervates
the palatoglossus of the tongue, and the majority of the muscles of the soft
palate.

80. Parasympathetic Functions
• In the thorax and abdomen, the vagus nerve is the main parasympathetic outflow
to the heart and gastro-intestinal organs.
• The Heart
Cardiac branches arise in the thorax, conveying parasympathetic innervation
to the sino-atrial and atrio-ventricular nodes of the heart .
These branches stimulate a reduction in the resting heart rate. They are
constantly active, producing a rhythm of 60 – 80 beats per minute. If the vagus
nerve was lesioned, the resting heart rate would be around 100 beats per
minute.

81. • Gastro-Intestinal System
• The vagus nerve provides parasympathetic innervation to the majority
of the abdominal organs.
• It sends branches to the oesophagus, stomach and most of the
intestinal tract – up to the splenic flexure of the large colon.
• The function of the vagus nerve is to stimulate smooth muscle
contraction and glandular secretions in these organs.
• For example, in the stomach, the vagus nerve increases the rate of
gastric emptying, and stimulates acid production.

82. • Purpose of the test
• To test the elevation of palate & contraction of pharynx
• To examine the movts of vocal cords
• Method of testing
• Notice the pitch & quality of voice, cough & difficulty in swallowing saliva
• Ask the Pt to open his mouth wide after a few movts ask to say “AH” while
breathing out & “UGH” while in
• The palate should move symmetrically upwards & backwards, the uvula in
mid line & two sides of pharynx contract symmetrically.

83. • Nerves are protected by myelin sheaths that serve to prevent the delicate nerve fibers from
damage and destruction;
• However, aberrations in normal biochemical environment due to excessive alcoholism or
persistently raised blood sugar levels can lead to swelling of myelin sheaths that lead to
permanent destruction of nerve fibers leading to inactivity of nerves.
• Other causes includes:
 inflammatory disorders,
 autoimmune destruction of nerves (in the setting of diseases like amyotrophic lateral
sclerosis, multiple sclerosis and other),
 viral infections and
 damage due to neoplastic conditions that press upon nerves causing mechanical damage.
• CLINICALANATOMY:

84. 1. Pain - most common nerve pain symptoms are due to pinched nerve (when nerve
exits through tiny foramina in the skull).
2. Organ Dysfunction - a branch or tributary of nerve is affected that leads to
localized symptoms of organ dysfunction due to damage to nerve fibers or
discrepancy in the synthesis of neurotransmitters.
3. Muscle Cramps - painfull and involuntary muscular contraction
4. Difficulty in Swallowing - Glottis is normally closed when a person is swallowing
in order to prevent the aspiration of food. This is managed by gag - reflex (gagging
sensation if the back of throat is touched). In patients of head injury or stroke, gag
reflex may get impaired leading to choking while eating and difficulty in swallowing.
5. Peptic Ulcer - Defects in the normal functioning of Vagus nerve may impair the
normal control mechanisms that modulate the gastric acid secretion. Excessive
secretion of peptic acid can lead to ulceration, dyspepsia and gastro- esophageal reflux
disease.

85. 6. Gastroparesis - under-activity of vagus nerve may interfere with the blood supply of
stomach after ingestion of food that leads to improper digestion. Gastroparesis is marked by
painful spasms in the stomach that affect normal food intake, heartburn, nausea and weight
loss.
7. Fainting - Over-activity of Vagus nerve increases the firing rate of receptors that presents
with sudden episodes of collapse and fainting (also referred to as vasovagal syncope).
Although, it is not dangerous, but fainting episodes may increase the risk of accidental injuries
that may prove life threatening.
8. Other Symptoms - Other symptoms include changes in the rhythm of heart, urinary
difficulties and changes in vocal tone.
• lesion to one of the RLN’s will cause dysphonia.
• A lesion to both RLN’s will cause aphonia (loss of voice) and a stridor (inspiratory
wheeze).
• Paralysis of the RLN’s usually occur due to cancer of the larynx or thyroid gland or due
to surgical complications.

86. The Accessory Nerve (CN XI)
• The Accessory Nerve (CN XI)
• The accessory nerve is the eleventh paired
cranial nerve.
• It has a purely somatic motor function,
innervating the sternocleidomastoid and
trapezius muscles.
• Anatomical Course
• Traditionally, the accessory nerve is
divided into spinal and cranial parts.

87. The spinal portion arises from neurons of the upper spinal
cord, specifically C1-C5/C6 spinal nerve roots.
These fibres coalesce to form the spinal part of the
accessory nerve, which then runs superiorly to enter the
cranial cavity via the foramen magnum.
The nerve traverses the posterior cranial fossa to reach
the jugular foramen.
It briefly meets the cranial portion of the accessory nerve,
before exiting the skull (along with the glossopharyngeal
and vagus nerves).
Outside the cranium, the spinal part descends along
the internal carotid artery to reach the
sternocleidomastoid muscle, which it innervates.
It then moves across the posterior triangle of the neck to
supply motor fibres to the trapezius
Spinal Component

88. The cranial portion is much smaller, and arises from the
lateral aspect of the medulla oblongata.
It leaves the cranium via the jugular foramen, where it
briefly contacts the spinal part of the accessory nerve.
Immediately after leaving the skull, cranial part combines
with the vagus nerve (CN X) at the inferior ganglion of
vagus nerve.
The fibres from the cranial part are then distributed
through the vagus nerve.
For this reason, the cranial part of the accessory nerve is
considered as part of the vagus nerve.
Cranial Component

89. Motor Function
• The spinal accessory nerve innervates two muscles –
the sternocleidomastoid and trapezius.
• Sternocleidomastoid
• Actions –
 Lateral flexion and rotation of the neck when
acting unilaterally
extension of the neck at the atlanto-occipital joints
when acting bilaterally.
• Trapezius
• Actions – It is made up of upper, middle and lower
fibres.
The upper fibres of the trapezius elevate the scapula
and rotate it during abduction of the arm.
The middle fibres retract the scapula .
The lower fibres pull the scapula inferiorly.

90. Clinical Relevance
• Examination of the Accessory Nerve
• The accessory nerve is examined by asking the patient to rotate their head and
shrug their shoulders, both normally and against resistance.
• Simply observing the patient may also reveal signs of muscle wasting in the
sternocleidomastoid and trapezius in cases of long-standing nerve damage.

91. • Palsy of the Accessory Nerve
• The most common cause of accessory nerve damage is iatrogenic (i.e. due to a
medical procedure).
• In particular, operations such as cervical lymph node biopsy or cannulation of
the internal jugular vein can cause trauma to the nerve.
• Clinical features include muscle wasting and partial paralysis of the
sternocleidomastoid, resulting in the inability to rotate the head or weakness in
shrugging the shoulders.
• Damage to the muscles may also result in an asymmetrical neckline.

92.  Congenital
Due to excessive stretching of sternocleidomastoid muscle
during labor.
• Injury to spinal part of accessory nerve
• Injury to brachial plexus
• Injury to nerve to platysma
CLINICAL FEATURES
Deformity where head is bent to one side and chin points to
opposite side.
Torticollis (wry neck):

93. Hypoglossal Nerve (CN XII)
• The hypoglossal nerve is the twelfth
paired cranial nerve.
• Its name is derived from ancient
Greek, ‘hypo‘ meaning under, and
‘glossal‘ meaning tongue.
• The nerve has a purely somatic
motor function, innervating the
majority of the muscles of the
tongue.

94. The hypoglossal nerve arises from the hypoglossal nucleus
in the medulla oblongata of the brainstem
It then passes laterally across the posterior cranial fossa,
within the subarachnoid space.
The nerve exits the cranium via the hypoglossal canal.
Now extracranial, the nerve receives a branch of
the cervical plexus that conducts fibres from C1/C2 spinal
nerve roots. These fibres do not combine with the
hypoglossal nerve – they merely travel within its sheath
It then passes inferiorly to the angle of the mandible,
crossing the internal and external carotid arteries, and
moving in an anterior direction to enter the tongue.
Anatomical Course

95. • Motor Function
• The hypoglossal nerve is responsible for motor innervation of the vast majority of
the muscles of the tongue (except for palatoglossus). These muscles can be
subdivided into two groups:
i) Extrinsic muscles
• Genioglossus (makes up the bulk of the tongue)
• Hyoglossus
• Styloglossus
• Palatoglossus (innervated by vagus nerve)
• ii) Intrinsic muscles
• Superior longitudinal
• Inferior longitudinal
• Transverse
• Vertical
• Together, these muscles are responsible for all movements of the tongue.

96. • Role of the C1/C2 Roots
• The C1/C2 roots that travel with the
hypoglossal nerve also have a motor
function.
• They branch off to innervate the
geniohyoid (elevates the hyoid bone)
and thyrohyoid (depresses the hyoid
bone) muscles.

97. Clinical Relevance
• Cranial Nerve Examination
• Purpose of the test
• To inspect the surface of the tongue
• To detect wasting, weakness & involuntary movements.
• To examine voluntary muscle control
• Method of testing
• Ask the Pt to protrude the tongue & observe for
• Reduction in size of affected side
• Excessive ridging & wrinkling
• Restricted protrusion
• Deviation towards one side

98. • Hypoglossal Nerve Palsy
• Damage to the hypoglossal nerve is a relatively
uncommon cranial nerve palsy. Possible causes
include head & neck malignancy and penetrating
traumatic injuries.
• If the symptoms are accompanied by acute pain, a
possible cause may be dissection of the
internal carotid artery.
• Patients will present with deviation of the tongue
towards the damaged side on protrusion, as well as
possible muscle wasting and fasciculations (twitching
of isolated groups of muscle fibres) on the affected
side.
Right hypoglossal
nerve palsy,
characterised by
deviation of the tongue
to the right.

99. Speech charecteristics
• The abnormality of the tongue leads to misarticulation
• The individual will have problem in producing t/d/l/n/j/k/g
• Due to dysarthria these individuals may have distorted vowel and
word flow

100. TO BE CONTINUED ……

101. THANK YOU