Transcript Functional Components of the Facial Nerve

The Facial Nerve:
Functional Components and
Anatomy
Brief overview of cranial nerve functional components
•
•
The 12 cranial nerves participate in a total of seven neural functions. Each of
these seven functions is designated by a three letter acronym.
The first letter is either G (General) or S (Special).
– General refers to primitive and/or external structures of the body.
– Special refers to senses unique to the head (taste, olfaction, hearing, vision, and
balance) and to muscles of branchial arch derivatives.
•
The second letter is either S (Somatic) or V (Visceral).
– Somatic refers to non-visceral structures including skin, muscles, tendons, joints,
retina (vision), basilar membrane (hearing), and utricle/saccula (balance).
– Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.
•
The third letter is either A (Afferent) or E (Efferent).
– Afferent refers to flow of neural information toward the brain (sensation)
– Efferent refers to flow of neural information toward the periphery (motor).
•
Knowledge of the functional components and the deficits that follow damage
to each provides the basis of the thorough neurological exam.
The Seven Functional Components
• GSA – General Somatic Afferent
– Touch, temperature, and pain from non-visceral structures
• GSE – General Somatic Efferent
– Motor to skeletal muscle
• GVA – General Visceral Afferent
– Touch (distention), temperature, and pain from the viscera
• GVE – General Visceral Efferent
– Motor to viscera, smooth muscle, and glands
• SSA – Special Somatic Afferent
– Vision, hearing, and balance
• SSE – Doesn’t exist
• SVA – Special Visceral Afferent
– Taste and olfaction
• SVE – Special Visceral Efferent
– Motor to muscles derived from the branchial arches
The remainder of this tutorial focuses on the
functional nerve components contained within the
facial nerve:
SVE
GVA
SVA
GVE
GSA
These components, either alone or in combination, make up the
facial nerve and its branches. An understanding of these
components can serve as a template for understanding the other
functional components. In addition, an understanding of the facial
nerve and its components can be applied in clinical situations to
help localize a patient’s defect.
Functional Components Within Branches of the
Facial Nerve:
• Greater Superficial Petrosal Nerve (GSPN)
– GVA, GVE, SVA
• Stapedial Nerve
– SVE
• Chorda Tympani Nerve
– GVE, SVA
• Posterior Auricular Nerve
– SVE, GSA
• Facial Nerve (terminal branch)
– SVE
Anatomy of Facial Nerve Branches
• The facial nerve exits the posterior cranial fossa (PCF) at the internal
acoustic meatus.
• Within the internal acoustic meatus the facial nerve enters the facial
canal.
• The first branch of the facial nerve, the greater superficial petrosal nerve
(GSPN) branches from the geniculate ganglion within the genu of the
facial canal and enters the middle cranial fossa by way of the hiatus of
the canal for the GSPN.
• The second branch of the facial nerve, the stapedial nerve, branches
from the descending portion of the facial nerve and enters the middle
ear.
• The third branch of the facial nerve, the chorda tympani nerve, branches
from the descending portion of the facial nerve and enters the middle
ear. Within the middle ear the chorda tympani nerve crosses the medial
surface of the tympanic membrane. It then passes through the
petrotympanic fissure to enter the infratemporal fossa.
• The descending portion of the facial nerve continues into the parotid
region by way of the stylomastoid foramen.
The facial nerve exits the posterior cranial
fossa (PCF) at the internal acoustic
meatus.
Within the internal acoustic meatus the
facial nerve enters the facial canal.
The first branch of the facial nerve, the
greater superficial petrosal nerve (GSPN)
branches from the geniculate ganglion
within the genu of the facial canal and
enters the middle cranial fossa by way of
the hiatus of the canal for the GSPN.
The second branch of the facial nerve, the
stapedial nerve, branches from the
descending portion of the facial nerve and
enters the middle ear.
The third branch of the facial nerve, the
chorda tympani nerve, branches from the
descending portion of the facial nerve and
enters the middle ear. Within the middle
ear the chorda tympani nerve crosses the
medial surface of the tympanic membrane.
It then passes through the petrotympanic
fissure to enter the infratemporal fossa.
The descending portion of the facial nerve
continues into the parotid region by way of
the stylomastoid foramen.
Functional components of the
Facial Nerve (CN VII)
1.
2.
3.
4.
5.
• SVE (Special Visceral Efferent) — Motor to
striated muscles derived from the 2nd branchial
arch.
• GVA (General Visceral Afferent) — Sensory from
visceral touch, temperature, and pain.
• SVA (Special Visceral Afferent) — Taste
• GVE (General Visceral Efferent) — Autonomic
innervation to mucosal, lacrimal, and salivary
glands.
• GSA (General Somatic Afferent) — Sensory
from somatic touch, temperature, and pain.
SVE Component of the
Facial Nerve
1.
2.
3.
4.
5.
The next 11 slides demonstrate innervation to
muscles derived from the 2nd branchial arch:
Stapedius muscle -- dampens movement of the
ossicles (inserts on stapes of middle ear)
Posterior auricular muscle -- posterior movement
of pinna
Stylohyoid muscle -- elevates hyoid bone
Posterior belly of digastric -- elevates hyoid
bone, depresses mandible
Muscles of facial expression -- blinking, smiling,
frowning, facial movements
1. The Stapedius muscle dampens movement of the ossicles
\
When a loud noise is heard by the ear:
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting into the middle ear
via the stapedial nerve.
• In the middle ear the stapedius muscle dampens
movement of the ossicles, protecting the inner ear from
damage from loud noises.
2. The Posterior Auricular nerve innervates the posterior
auricular muscle, pulling the pinna posteriorly.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the posterior
auricular nerve branches from the facial nerve and via
the SVE component of the posterior auricular nerve the
posterior auricular muscle pulls the pinna posteriorly.
3. The Stylohyoid muscle elevates the hyoid bone
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the stylohyoid
branch of the facial nerve innervates the stylohyoid
muscle.
• The Stylohyoid muscle elevates the hyoid bone.
4. The Posterior belly of digastric muscle elevates the
hyoid bone
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the Posterior belly
of the digastric branch of the facial nerve innervates the
posterior belly of the digastric muscle.
• The posterior belly of digastric muscle elevates the hyoid
bone
5. The next six slides demonstrate SVE innervation to
the muscles of facial expression*
A.
Temporal branch (with zygomatic branch) innervates orbicularis
oculi--closes eyelids
B.
Zygomatic branch (with buccal branch) innervates zygomaticus
major--smiling
C.
Buccal branch innervates
buccinator--tenses cheek
D.
Mandibular branch innervates depressor angularis oris--frowning
E.
Cervical branch innervates platysma -- lowers mandible, tenses
skin of anterior neck
*These are key innervations to the muscles of facial expression.
However, each nerve branch innervates multiple muscles and each
muscle receives multiple nerve branches.
A. The temporal and zygomatic branches of the facial
nerve provide SVE nerve fibers that innervate the
ipsilateral orbicularis oculi, the muscle responsible for
closing the eyelid.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the temporal and
zygomatic branches of the facial nerve innervate the
orbicularis oculi muscle.
• Contraction of orbicularis oculi causes the eyelid to
close.
B. The zygomatic and buccal branches of the facial nerve
innervate the ipsilateral zygomaticus major muscle, the
main muscle responsible for smiling.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the zygomatic and
buccal branches of the facial nerve innervate the
zygomaticus major muscle.
• Contraction of the zygomaticus major muscle causes
smiling.
C. The buccal branch of the facial nerve innervates the
buccinator muscle, the muscle responsible for holding
the cheek against the teeth, thus positioning food for
chewing.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the buccal branch
of the facial nerve innervates the buccinator muscle.
• Contraction of the buccinator muscle causes tensing of
the cheek which helps position food within the occusal
plane for chewing
D. The mandibular and buccal branches of the facial nerve
innervate the ipsilateral depressor angularis oris muscle,
a muscle responsible for frowning.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the mandibular
branch of the facial nerve innervates the depressor
angularis oris muscle.
• Contraction of the depressor angularis oris muscle
causes frowning.
E. The cervical branch of the facial nerve innervates the
platysma muscle, a muscle partly responsible for
depressing the mandible.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the cervical
branch of the facial nerve innervates the platysma
muscle.
• Contraction of the platysma muscle results in depression
of the mandible.
E. The cervical branch of the facial nerve innervates the
platysma muscle (the “shaving muscle”), a muscle
responsible for tightening the skin of the anterior neck.
\
• SVE sends a signal from the motor nucleus of the facial
nerve, through the internal acoustic meatus, traveling
through the facial canal until exiting at the stylomastoid
foramen.
• After exiting the stylomastoid foramen the cervical
branch of the facial nerve innervates the platysma
muscle.
• Contraction of the platysma muscle causes the skin of
the anterior neck to tighten.
Summary of SVE
1. A nerve signal is transmitted from the facial nucleus, through the internal
acoustic meatus, to the middle ear where stapedius muscle contraction
dampens movement of the ossicles.
2. A nerve signal is transmitted from the facial nucleus, through the internal
acoustic meatus, through the stylomastoid foramen to the temporal
(orbicularis oculi closes eyelids), zygomatic (zygomaticus major muscle
partly responsible for smiling), buccal (buccinator tenses cheek), mandibular
(depressor angularis oris responsible for frowning), and cervical (platysma
helps lower mandible and tightens skin of neck) branches of the facial
nerve.
3. A nerve signal is transmitted from the facial nucleus, through the internal
acoustic meatus, through the stylomastoid foramen, to the posterior belly of
the digastric muscle, which elevates the hyoid bone.
4. A nerve signal is transmitted from the facial nucleus, through the internal
acoustic meatus, through the stylomastoid foramen, to the stylohyoid
muscle, which elevates the hyoid bone.
5. A nerve signal is transmitted from the facial nucleus, through the internal
acoustic meatus, through the stylomastoid foramen, to the posterior
auricular muscle, which is responsible for posterior displacement of the
pinna.
GVA Component of the Facial
Nerve
The next slide demonstrates that GVA is
responsible for providing:
1. Light touch, temperature, and pain
sensation from the soft palate via the
greater superficial petrosal nerve
(GSPN).
1. GVA provides sensation of light touch,
temperature, and pain from the soft palate.
•
•
•
•
When the soft palate encounters an extreme temperature,
is touched lightly, or is subject to a painful stimulus:
A nerve signal is sent via the GVA component through
the lesser palatine canal. The GVA component then
becomes part of the GSPN.
As part of the GSPN the GVA component travels to the
lacerate foramen, and then through the hiatus of the
canal of the GSPN.
At the geniculate ganglion, the GVA component
becomes part of the facial nerve.
The nerve signal travels along the GVA component of
the facial nerve and passes through the internal acoustic
meatus. After passing through the internal acoustic
meatus the nerve signal from the soft palate reaches the
brainstem.
Summary of GVA
• A nerve signal is transmitted through the lesser palatine
canal, to the lacerate foramen, through the hiatus of the
canal of the greater superficial petrosal nerve, and
through the internal acoustic meatus to provide light
touch, temperature, and pain from the soft palate.
SVA Component of the
Facial Nerve
The next two slides demonstrate that SVA
is responsible for providing:
1. Taste from the hard and soft palate via
the greater superficial petrosal nerve
(GSPN).
2. Taste from the anterior 2/3 of the
tongue via the chorda tympani nerve.
1. SVA provides taste sensation from the hard and
soft palate via the GSPN.
•
•
•
•
When food or drink, such as coffee sweetened with
sugar, comes in contact with the hard and soft palate:
A nerve signal is sent via the SVA component
through the lesser palatine canal. The SVA
component then becomes part of the GSPN.
As part of the GSPN the SVA component travels to
the lacerate foramen, and then through the hiatus of
the canal of the GSPN.
At the geniculate ganglion, the SVA component
becomes part of the facial nerve.
The nerve signal travels along the SVA component of
the facial nerve and passes through the internal
acoustic meatus. After passing through the internal
acoustic meatus the nerve signal from the hard and
soft palate reaches the brainstem.
2. SVA provides taste to the anterior 2/3 of the
tongue via the chorda tympani nerve.
•
•
•
•
When a drink or food item, such as a lollipop, comes
in contact with the anterior 2/3 of the tongue:
A nerve signal is sent via the SVA component.
Fibers from the SVA component then join with fibers
from the GVE component to form the chorda tympani
nerve.
The chorda tympani nerve passes through the
petrotympanic fissure and across the medial surface
of the tympanic membrane.
The chorda tympani nerve fibers then become part of
the facial nerve. As part of the facial nerve the SVA
fibers pass through the internal acoustic meatus.
After passing through the internal acoustic meatus
the nerve signal from the anterior 2/3 of the tongue
reaches the brainstem.
Summary of SVA Pathways
1.
2.
A nerve signal is transmitted through the greater and
lesser palatine canals, to the lacerate foramen,
through the hiatus of the canal of the greater
superficial petrosal nerve, and through the internal
acoustic meatus to provide taste from the hard and
soft palate.
A nerve signal is transmitted through the
petrotympanic fissure and through the internal
acoustic meatus to provide taste from the anterior 2/3
of the tongue.
GVE Component of the
Facial Nerve
1. Via the pterygopalatine ganglion GVE provides:
A. Lacrimation (tearing of the eye)
B. Mucus secretions of the nasal cavity
C. Mucus secretions of the oral cavity
2. Via innervation of the submandibular ganglion
GVE provides:
A. Salivation of the oral cavity
1. The GVE component of the facial nerve transmits preganglionic
fibers to the pterygopalatine ganglion via the GSPN. From the
pterygopalatine ganglion postganglionic fibers cause ipsilateral
lacrimation and mucus secretions of the nasal and oral cavities.
•
GVE fibers send a signal from the lacrimal nucleus,
through the internal acoustic meatus. The nerve signal
travels along the GVE component of the facial nerve
•
At the geniculate ganglion the nerve signal travels
along preganglionic GVE fibers of the GSPN to the
Vidian nerve and to the pterygopalatine ganglion.
•
From the pterygopalatine ganglion postganglionic GVE
fibers carry the nerve signal to cause ipsilateral tearing
of the eye, mucus secretions of the nasal cavities, and
mucus secretions of the hard and soft palate.
2. The GVE component of the facial nerve transmits preganglionic
fibers to the submandibular ganglion via the chorda tympani nerve.
From the submandibular ganglion postganglionic fibers innervate the
submandibular and sublingual glands, causing salivation.
•
•
•
GVE sends a signal from the superior salivary nucleus,
through the internal acoustic meatus. The nerve signal
travels along the GVE component of the facial nerve.
At the point that the chorda tympani nerve branches
from the facial nerve the nerve signal travels along
preganglionic GVE fibers of the chorda tympani nerve,
through the petrotympanic fissure, to the
submandibular ganglion.
From the submandibular ganglion postganglionic GVE
fibers carry the nerve signal to cause salivation from
the submandibular and sublingual glands.
Summary of GVE
1.
2.
From the superior salivary and lacrimal nucleus a nerve
signal is transmitted through the internal acoustic meatus,
through the hiatus of the canal of the GSPN, to the lacerate
foramen, and through the pterygoid canal to the
pterygopalatine ganglion. From the pterygopalatine
ganglion postganglionic GVE fibers provide lacrimation of
the eyes and mucus secretion of the nasal cavity and oral
cavity.
From the superior salivary and lacrimal nucleus a nerve
signal is transmitted through the internal acoustic meatus
and through the petrotympanic fissure to the submandibular
ganglion. From the submandibular ganglion postganglionic
GVE fibers provide salivation in the oral cavity.
GSA Component of the
Facial Nerve
GSA is responsible for providing:
1. Touch, temperature, and pain sensation from
part of the external acoustic meatus via the
posterior auricular nerve.
1. GSA provides touch, temperature, and pain
sensation from the external acoustic meatus.
•
•
•
•
When the external acoustic meautus encounters an
extreme temperature, is touched, or is subject to a
painful stimulus:
A nerve signal is sent via the GSA component of the
posterior auricular nerve.
The nerve signal continues to travel along the GSA
component as part of the descending portion of the facial
nerve and passes through the stylomastoid foramen.
From the stylomastoid foramen the nerve signal
continues to travel along the GSA component of the
facial nerve and passes through the internal acoustic
meatus.
After passing through the internal acoustic meatus the
nerve signal from the external acoustic meatus reaches
the brainstem.
Summary of GSA
• A nerve signal is transmitted from the external
acoustic meatus, through the stylomastoid
foramen, and through the internal acoustic
meatus to provide touch, temperature, and pain
sensation from the external acoustic meatus.
Summary of functional components
• Each of the five functional components of the
facial nerve SVE, GVA, SVA, GVE, and GSA
have a unique function. Knowledge of these
functional components can be applied to clinical
observations to aid in localizing lesions of nerve
branches or at anatomical landmarks.
• The following slides provide examples of how
lesions at different locations can effect function.
Lesion #1
One effect of a lesion located between the
branching of of the stapedial nerve and the
branching of the chorda tympani nerve would be
paralysis of facial muscles.
Lesion #2
Another effect of a lesion located between the
branching of the stapedial nerve and the
branching of the chorda tympani nerve would be
loss of taste of anterior 2/3 of the tongue.
Lesion #3
One effect of a lesion located at the stylomastoid
foramen would be partial loss of sensation of the
external acoustic meatus.
Lesion #4
A lesion located between the branching of the
GSPN and the branching of the stapedial nerve
will spare taste of the hard palate.
Lesion #5
A lesion located between the branching of the
GSPN and the branching of the stapedial nerve
will also spare light touch sensation from the soft
palate.
Thank You
Return to SVE
Return to GVA
Return to GVE
Return to SVA
Return to GSA
Return to Lesions
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing sensation from the soft palate.
Please try again
Incorrect
The stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud
noises.
Please try again
Incorrect
The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the hard palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
Incorrect
The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the soft palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing temperature sensation from
the soft palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
Incorrect
The GVE component of the chorda tympani nerve, which is spared
by this lesion, is responsible for providing salivation
of the oral cavity.
Please try again
Incorrect
The stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud
noises.
Please try again
Incorrect
This lesion will not spare taste to the anterior 2/3 of the tongue,
which is supplied via the SVA component of the chorda tympani
nerve.
Please try again
Incorrect
This lesion will not spare salivation of the oral cavity, which is
supplied by the GVE component of the chorda tympani nerve.
Please try again
Incorrect
This lesion will not spare ipsilateral facial expression, which is
supplied by the temporal, zygomatic, buccal, mandibular, and
cervical branches of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to taste from the anterior 2/3 of
the tongue, which is supplied by the SVA component of the chorda
tympani nerve.
Please try again
Incorrect
This lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to protect the ear from loud
noises, which is supplied by the stapedial nerve (SVE).
Please try again
Correct!
A lesion here will cause paralysis of facial muscles due
to its disruption of the SVE component.
Go back to question 1
Next question
Correct!
A lesion here will cause a loss of taste to the anterior 2/3 of the
tongue due to the disruption of the SVA component of
the chorda tympani nerve.
Go back to question 2
Next question
Correct!
A lesion here will cause partial loss of sensation (light touch,
temperature, and pain) of the external acoustic meatus due to
disruption of the GSA component of the posterior auricular nerve.
Go back to question 3
Next question
Correct!
A lesion here will spare a person’s ability to taste on the hard and soft
palate because the SVA component of the Greater Superficial Petrosal
Nerve (GSPN) remains intact.
Go back to question 4
Next question
Correct!
A lesion here will spare the sensation of light touch of the soft palate
because the GVA component of the GSPN remains intact.
Go back to question 5
Continue