Transcript Cranial Nerve VII: 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.
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen Inferior Orbital Fissure
Posterior Cranial Fossa (PCF)
Internal Acoustic Meatus Facial canal Greater superficial Petrosal nerve (GSPN) Pterygoid canal Petrotympanic fissure Greater and lesser palatine canals Facial nerve Stylomastoid Foramen Chorda tympani nerve Facial nerve Posterior auricular N.
The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic meatus .
Click here to start Animation
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen Inferior Orbital Fissure
Posterior Cranial Fossa
Internal Acoustic Meatus Facial canal Greater superficial Petrosal nerve (GSPN) Pterygoid canal Petrotympanic fissure Facial nerve Stylomastoid Foramen Chorda tympani Facial nerve Posterior auricular N.
Within the internal acoustic meatus the facial nerve enters the facial canal.
Click here to start Animation Greater and lesser palatine canals
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve
Geniculate ganglion
Lacerate foramen
Posterior Cranial Fossa
Internal Acoustic Meatus Facial canal
MCF
Greater superficial Petrosal nerve (GSPN) Pterygoid canal Petrotympanic fissure Inferior Orbital Fissure Greater and lesser palatine canals Facial nerve Stylomastoid Foramen Chorda tympani Facial nerve
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 (MCF) by way of the hiatus of the canal for the GSPN.
Click here to start Animation
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen
Posterior Cranial Fossa
Internal Acoustic Meatus Facial canal Inferior Orbital Fissure Greater superficial Petrosal nerve (GSPN) Pterygoid canal Stapedial N.
Petrotympanic fissure Greater and lesser palatine canals Facial nerve Stylomastoid Foramen Chorda tympani Facial nerve Posterior auricular N.
The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.
Click here to start Animation
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen Inferior Orbital Fissure
Posterior Cranial Fossa
Internal Acoustic Meatus Facial canal Greater superficial Petrosal nerve (GSPN) Pterygoid canal Petrotympanic fissure Greater and lesser palatine canals Facial nerve Chorda tympani N.
Stylomastoid Foramen
Infratemporal fossa
Facial nerve
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.
Click here to start Animation
Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen Inferior Orbital Fissure
Posterior Cranial Fossa
Internal Acoustic Meatus Facial canal Greater superficial Petrosal nerve (GSPN) Pterygoid canal Petrotympanic fissure Facial nerve Stylomastoid Foramen Chorda tympani Facial nerve Posterior auricular N.
Parotid region The descending portion of the facial nerve exits the facial canal at the stylomastoid foramen and continues into the parotid region
Click here to start Animation Greater and lesser palatine canals
Functional components of the Facial Nerve (CN VII)
1.
2 .
3.
4.
5 .
• SVE (Special Visceral Efferent) — Motor to striated muscles derived from the 2
nd
branchial arch.
• GVA (General Visceral Afferent) — Sensory from visceral touch, temperature, and pain.
• SVA (Special Visceral Afferent) glands.
— Taste • GVE (General Visceral Efferent) — Autonomic innervation to mucosal, lacrimal, and salivary • GSA (General Somatic Afferent) — Sensory from somatic touch, temperature, and pain.
Click on numbers for functional components
SVE Component of the Facial Nerve
1.
The next 11 slides demonstrate innervation to muscles derived from the 2 nd branchial arch: Stapedius muscle -- dampens movement of the ossicles (inserts on stapes of middle ear) 2. Posterior auricular muscle -- posterior movement of pinna 3. Stylohyoid muscle -- elevates hyoid bone 4. Posterior belly of digastric -- elevates hyoid bone, depresses mandible 5. Muscles of facial expression -- blinking, smiling, frowning, facial movements Click here to start Animation of SVE component
1.
The Stapedius muscle dampens movement of the ossicles
SVE
\
Stapedius muscle dampens movement of the ossicles protecting the inner ear from damage from loud noises Click here to start Animation
2. The Posterior Auricular nerve innervates the posterior auricular muscle, pulling the pinna posteriorly.
SVE
Posterior auricular muscle pulls the pinna posteriorly SVE component of posterior auricular nerve Click here to start Animation
3. The Stylohyoid muscle elevates the hyoid bone
SVE
Through the internal Acoustic meatus Stylohyoid muscle elevates the hyoid bone.
Through the stylomastoid foramen Stylohyoid branch of facial nerve innervates stylohyoid muscle Click here to start Animation
4. The Posterior belly of digastric muscle elevates the hyoid bone
SVE
Through the internal acoustic meatus Posterior belly of digastric muscle elevates the hyoid bone Through the stylomastoid foramen Posterior belly of digastric branch of facial nerve innervates posterior belly of digastric muscle.
Click here to start Animation
5. The next six slides demonstrate SVE innervation to the muscles of facial expression*
SVE 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.
E.
Mandibular branch innervates depressor angularis oris--frowning 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
Contraction of orbicularis oculi causes the eyelid to close Temporal branch Zygomatic branch Click here to start Animation
B. The zygomatic and buccal branches of the facial nerve innervate the ipsilateral zygomaticus major muscle, the main muscle responsible for smiling.
SVE Zygomaticus major muscle
Zygomatic branch Click here to start Animation 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
Contraction of the buccinator muscle causes tensing of the cheek which helps position food within the occusal plane for chewing Buccal branch of facial nerve innervates Buccinator muscle. Click here to start Animation
D. The mandibular and buccal branches of the facial nerve innervate the ipsilateral depressor angularis oris muscle, a muscle responsible for frowning.
SVE
Mandibular branch Depressor angularis oris Click here to start Animation 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
Contraction of platysma Muscle results in depression of mandible.
Platysma muscle Cervical branch of facial nerve innervates Platysma muscle.
Click here to start Animation
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
Contraction of platysma muscle causes the skin of the anterior neck to tighten.
Platysma muscle Cervical branch of facial nerve innervates Platysma muscle.
Click here to start Animation
Summary of SVE
Facial nucleus Internal Acoustic Meatus Facial nerve Facial canal Stapedius muscle dampens movement of ossicles.
Stylomastoid Foramen Posterior auricular N.
Posterior auricular muscle responsible for posterior displacement of pinna.
Facial nerve Stylohyoid muscle elevates hyoid bone.
Posterior belly of digastric elevates hyoid bone.
Click here to start Animation Temporal-orbicularis oculi closes eyelids.
Zygomatic-zygomaticus major partly responsible for smiling.
Buccal-buccinator tenses cheek Mandibular-depressor angularis oris responsible for frowning.
Cervical- platysma helps lower mandible and tightens skin of neck.
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).
Click here to start GVA
GVA
1. GVA provides sensation of light touch, temperature, and pain from the soft palate.
GSPN Temperature sensation
soft palate
Light touch sensation Pain sensation Facial nerve
Light touch, temperature, and pain from the soft palate Click here for animation
Summary of GVA
Through the internal acoustic meatus Facial canal Through the hiatus of canal of GSPN Through the Pterygoid canal
GSPN
Pterygoid canal
Facial nerve
Through the lesser palatine canal Light touch, temperature, and pain from the soft palate Click here for animation
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.
Click here for animation
1. SVA provides taste sensation from the hard and soft palate via the GSPN.
SVA
Hard palate Soft palate
GSPN branches from the facial nerve at the geniculate ganglion within the genu of the facial canal. It is made up of fibers from SVA , GVE , and GVA .
Co
Sweetened coffee
Taste from the hard and soft palate Click here for animation
2. SVA provides taste to the anterior 2/3 of the tongue via the chorda tympani nerve.
SVA
Taste from the anterior 2/3 of the tongue
Chorda tympani
Click here for animation
Summary of SVA
Internal Acoustic Meatus Hiatus of canal of greater superficial petrosal nerve Lacerate foramen Facial canal GSPN Pterygoid canal Petrotympanic fissure Greater and lesser palatine canals Chorda tympani Taste from hard and soft palate.
Taste from anterior 2/3 tongue.
Stylomastoid Foramen Click here to start animation
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 Click to start Animation of GVE component
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 GSPN Lacrimal gland Pterygopalatine ganglion
A. Tearing of eye
Lacrimal nucleus
B. Mucus secretion of nasal cavities C. Mucus secretion of hard and soft palate.
Click here to start Animation
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
Sublingulal gland Submandibular gland
Superior salivary nucleus Chorda tympani Submandibular ganglion
Click here to start Animation
Summary of GVE
Internal Acoustic Meatus
Superior salivary and lacrimal nucleus
Hiatus of canal of greater superficial petrosal nerve Lacerate foramen
GSPN
Facial canal Inferior Orbital Fissure Greater and lesser palatine canals Pterygoid canal From the pterygopalatine ganglion postganglionic GVE fibers provide lacrimation of the eyes and mucus secretion of the nasal cavity and oral cavity.
Petrotympanic fissure
Chorda tympani
Click here to start animation 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.
Click here to start GSA
1. GSA provides touch, temperature, and pain sensation from the external acoustic meatus.
Cotton swab
GSA
Touch, temperature, and pain sensation from part of the external acoustic meatus.
Posterior auricular nerve Click here to start animation
Foramen Rotundem Inferior Orbital Fissure
Summary of GSA
Internal Acoustic Meatus Facial canal Facial nerve Stylomastoid Foramen Facial nerve Touch, temperature, and pain sensation from the external acoustic meatus.
Posterior auricular nerve Click here to start animation
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.
Question #1
One effect of a lesion here, between the branching of the stapedial nerve and the branching of the chorda tympani nerve, would be:
Question #2
A lesion here, between the branching of the stapedial nerve and the branching of the chorda tympani nerve, will also cause?
A . Loss of light touch from the soft palate
B. Loss of taste from the soft palate
C. Loss of taste of anterior 2/3 of tongue
D. Loss of temperature from the soft palate.
Question #3
One effect of a lesion here, at the stylomastoid foramen will be:
A . Loss of light touch from the soft palate
B. Loss of salivation of oral cavity
C. Increased sensitivity to loud noises
D.Partial loss of sensation of external acoustic meatus
Question #4
A lesion here, between the branching of the GSPN and the branching of the stapedial nerve, will spare:
A . Taste of anterior 2/3 of tongue
D. Ipsilateral facial expression
Question #5
A lesion here, between the branching of the GSPN and the branching of the stapedial nerve, will also spare:
A. Light touch from the soft palate
C. Taste from the anterior 2/3 of tongue
D. Protection of the inner ear from loud noises
Thank You
Incorrect
The
GVA
component of the GSPN, which is spared by this lesion, is responsible for providing sensation from the soft palate.
Incorrect
The stapedial nerve (
SVE
), which is spared by this lesion, is responsible for protecting the ear from increased sensitivity to loud noises.
Incorrect
The
SVA
component of the GSPN, which is spared by this lesion, is responsible for providing taste from the hard palate.
Incorrect
The
GVA
component of the GSPN, which is spared by this lesion, is responsible for providing light touch from the soft palate.
Incorrect
The
SVA
component of the GSPN, which is spared by this lesion, is responsible for providing taste from the soft palate.
Incorrect
The
GVA
component of the GSPN, which is spared by this lesion, is responsible for providing temperature sensation from the soft palate.
Incorrect
The
GVA
component of the GSPN, which is spared by this lesion, is responsible for providing light touch from the soft palate.
Incorrect
The
GVE
component of the chorda tympani nerve, which is spared by this lesion, is responsible for providing salivation of the oral cavity.
Incorrect
The stapedial nerve (
SVE
), which is spared by this lesion, is responsible for protecting the ear from increased sensitivity to loud noises.
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.
Incorrect
This lesion will not spare salivation of the oral cavity, which is supplied by the
GVE
component of the chorda tympani nerve.
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
).
Incorrect
This lesion will not spare the ability to smile, which is supplied by the zygomatic branch of the facial nerve (
SVE
).
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.
Incorrect
This lesion will not spare the ability to smile, which is supplied by the zygomatic branch of the facial nerve (
SVE
).
Incorrect
This lesion will not spare the ability to protect the ear from loud noises, which is supplied by the stapedial nerve (
SVE
).
Correct!
A lesion here will cause paralysis of facial muscles due to its disruption of the
SVE
component.
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.
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.
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.
Correct!
A lesion here will spare the sensation of light touch of the soft palate because the
GVA
component of the GSPN remains intact.