seminar on facial nerve (7th cranial nerve)

1. FACIAL NERVE
PRESENTED BY-
DR. CHHAVI SAIGAL
1ST YEAR MDS

2. CONTENT
1. Introduction
2. Nuclei of Origin
3. Functional Component
4. Course and Relations
5. Branches and Distribution
6. Ganglia Associated with Facial Nerve
7. Applied Aspects

3. INTRODUCTION
• Nervus facialis
• Facial nerve is the 7th cranial nerve.
• It is a mixed nerve with both motor and sensory roots
(nerve of wrisberg).
• It is a nerve of 2nd branchial arch.
• It emerges from the brainstem at ponto-medullary
junction.

4. NUCLEI
• Fibres of facial nerve are connected to following nuclei -
1. Motor Nucleus (branchiomotor)-lies in lower part of
pons
2. Superior Salivatory Nucleus (parasympathetic)-lies in
dorsal part of pons)
3. Lacrimatory Nucleus (parasympathetic)- lower pons
4. Nucleus of Tractus Solitarius (lies in medulla)
5. Spinal nucleus of 5th nerve

5. FUNCTIONAL COMPONENTS
GVE
Secretomotor
to
submandibular,
sublingual,lacri
mal glands,
palate and
pharynx.
SVE
Muscles of
facial
expression
and for
elevation of
hyoid bone.
GVA
Carries afferent
impulses from
submandibular
gland,
sublingual
gland and
lacrimal glands.
SVA
Taste
sensation
from palate
and ant. 2/3rd
of tongue
except from
vallate papilla
GSA
Proprioceptiv
e fibres.Nerve
does not give
direct
branches to
the ear but
some fibres
may reach it
through
communicati
on with vagus
nerve.

7. ORIGIN AND INTRACRANIAL COURSE
• It is attached to the
brainstem at ponto-
medullary junction by 2
roots-
motor (large,medially)
sensory(smaller,laterally)
• Facial nerve leave the
posterior cranial fossa by
entering internal
acoustic meatus.

8. COURSE AND RELATIONS
• In the internal acoustic meatus, motor
root lies in a groove on the 8th nerve
with sensory root intervening.
• Are accompanied by labyrinthine
vessels.
• At the fundus of the meatus, 2 roots
fuse to form single trunk which lies in
the facial canal of petrous temporal
bone.

9. INTRA-PETROUS
• After entering the internal acoustic meatus,it
enters a bony canal through the roof of middle
ear.
• Runs laterally above the vestibule to reach
antero-superior surface of medial wall of
middle ear.
• Bends sharply backward above the
promontory.Nerve then runs horizontally
backward in a canal projecting into medial
wall of middle ear.
• Reaching the junction of medial and posterior
wall of middle ear, it is directed vertically
downward behind the promontory.
• It leaves the skull by passing through
stylomastoid foramen.

10. Intraparotid/Extracranial Course-
• It crosses the lateral side of base of styloid process and enters the
posteromedial surface of parotid gland.
• Runs forward through the gland crossing retromandibular vein and
external carotid artery.
• Within the parotid gland, it divides into 5 terminal motor branches.

11. BRANCHES AND DISTRIBUTION
• Within the facial canal- • At its exit from stylomastoid
foramen-
Greater Petrosal Nerve
Nerve to Stapedius
Chorda tympani
Posterior Auricular
Digastric
Stylohyoid

12. • Terminal branches within the
parotid gland-
• Communicating branches with
adjacent cranial and spinal
nerves.
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical

14. 1. Greater petrosal nerve- Preganglionic secretomotor fibres
Greater petrosal nerve joins deep petrosal nerve
Forms nerve of pterygoid canal
Relay in sphenopalatine ganglia
zygomatic nerve joins lacrimal nerve
Supplies lacrimal gland.
2. Nerve to stapedius-
• It arises opposite the pyramid of middle ear.
• Supplies stapedius muscle.

15. 3. Chorda tympani-
• Arises in the facial canal about 6mm above
the stylomastoid foramen.
• Runs forward in a bony canal,enters the
middle ear through posterior wall. Runs
forward in close relation to tympanic
membrane.
• Enters the anterior canaliculus leaving the
middle ear by passing through petro-tympanic
fissure.
• It then passes medial to the spine of
sphenoid and enters the infratemporal fossa
where it joins lingual nerve.
• Carries preganglionic secretomotor fibres to
submandibular ganglion for supply of
submandibular and sublingual salivary glands
+ taste fibres from anterior 2/3rd of tongue.

16. 4. Posterior auricular-
Arises just below the stylomastoid foramen
Ascends between mastoid process and external acoustic meatus
Supplies Auricularis posterior, Occipitalis and Intrinsic muscle on back of
auricle.
5. Digastric branch-
• It supplies posterior belly of digastric.
6. Stylohyoid branch-
• Supplies stylohyoid muscle.

17. FIVE TERMINAL BRANCHES

18. GANGLIA ASSOCIATED
• GENICULATE GANGLIA-
 Located on the 1st bend of facial nerve.
 Sensory ganglion.
• SUBMANDIBULAR GANGLIA-
 Parasympathetic ganglion
 Relay of secretomotor fibres to submandibular and sublingual glands.
• PTERYGOPALATINE GANGLIA-
 Parasympathetic ganglion, suspended by 2 roots of maxillary nerve.
 Preganglionic secretomotor fibres to lacrimal gland relay in this ganglia.

19. APPLIED ASPECTS-
Lesions of facial nerve are of 2 types-
• Supranuclear or Upper motor neuron
• Infranuclear or Lower motor neuron
Upper motor neuron lesion-
• UMN lesion spares the upper part of face because it is
innervated by corticonuclear fibres of both the cerebral
hemispheres.
• UMN lesion results in the paralysis of only lower half of
opposite side of face.
Lower motor neuron lesion-
• A LMN lesion causes ipsilateral paralysis of the whole
side of face on same side.
• Muscles in the lower part of face receive input
from the contralateral hemisphere only.

20. Bell’s palsy- Common
infranuclear lesion is bell’s
palsy.
Ipsilateral Paralysis of facial
nerve due to its compression
in facial canal at the
stylomastoid foramen.
• CAUSES- Infection in middle
ear, compression of the nerve
due to cold near stylomastoid
foramen.

21. ACCORDING TO THE SITE OF INFRANUCLEAR LESION-

22. 2. Crocodile tears syndrome-
• Efferent fibres from superior salivatory
nucleus become improperly connected to
nerve axons projecting to lacrimal glands.
• Causes one to shed tears during salivation.
3. Ramsay-hunt syndrome-
• Involvement of geniculate ganglion by herpes
zoster results in this syndrome.
• Symptoms-
1. Hyperacusis
2. Loss of lacrimation
3. Loss of sensation of taste in anterior 2/3rd of
tongue.
4. Bell’s palsy and lack of salivation.
5. Vesicular rash on external ear.