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title, docid, authors, breadcrumbs, category, cmeTopicId, documentVersionId, imageCount, lastUpdated, pageDescription, pageKeywords, pageTitle, enhancedTitle, type, breadcrumbs
title docid authors breadcrumbs category cmeTopicId documentVersionId imageCount lastUpdated pageDescription pageKeywords pageTitle enhancedTitle type breadcrumbs
Facial Nerve (CNVII) 2f4818dd-6438-405b-8561-5cbbb9c91562
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94f835c8-fa13-4e8a-995b-53048e6b0605 Philip R. Chapman, MD
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b0a6efa4-ad68-430c-b5da-f5c904adf809 Ryan P. Cabeen, PhD
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Brain brain 6d8829f1-14d7-45af-8675-255189aa526a
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Anatomy anatomy 45a4cfd4-910b-4f11-8eba-c887895fdbf8
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Skull Base and Cranial Nerves skull-base-and-cranial-nerves 95ed8b31-2615-40e8-befe-a6a742a0872a
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Facial Nerve (CNVII) facial-nerve-cnvii null
Brain e4cb8b15-b95c-4309-b9d9-c9719f291581 b4c5e191-d167-409d-9300-1c0a03b77e1a 27 10/20/20 Facial Nerve (CNVII) Brain, Anatomy, Skull Base and Cranial Nerves, Facial Nerve (CNVII) Facial Nerve (CNVII) | STATdx Facial Nerve (CNVII) ANATOMY
Brain
Anatomy
Skull Base and Cranial Nerves
Facial Nerve (CNVII)

title: "Facial Nerve (CNVII)" docid: "2f4818dd-6438-405b-8561-5cbbb9c91562" authors:

  • key: "94f835c8-fa13-4e8a-995b-53048e6b0605" value: "Philip R. Chapman, MD"
  • key: "b0a6efa4-ad68-430c-b5da-f5c904adf809" value: "Ryan P. Cabeen, PhD" breadcrumbs:
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  • name: "Anatomy" slug: "anatomy" treeNodeId: "45a4cfd4-910b-4f11-8eba-c887895fdbf8"
  • name: "Skull Base and Cranial Nerves" slug: "skull-base-and-cranial-nerves" treeNodeId: "95ed8b31-2615-40e8-befe-a6a742a0872a"
  • name: "Facial Nerve (CNVII)" slug: "facial-nerve-cnvii" treeNodeId: null category: "Brain" cmeTopicId: "e4cb8b15-b95c-4309-b9d9-c9719f291581" documentVersionId: "b4c5e191-d167-409d-9300-1c0a03b77e1a" imageCount: 27 lastUpdated: "10/20/20" pageDescription: "Facial Nerve (CNVII)" pageKeywords: "Brain, Anatomy, Skull Base and Cranial Nerves, Facial Nerve (CNVII)" pageTitle: "Facial Nerve (CNVII) | STATdx" enhancedTitle: "Facial Nerve (CNVII)" type: "ANATOMY" breadcrumbs:
  • "Brain"
  • "Anatomy"
  • "Skull Base and Cranial Nerves"
  • "Facial Nerve (CNVII)"

TERMINOLOGY

  • Abbreviations

    • Facial nerve (CNVII)

  • Synonyms

    • 7th cranial nerve

  • Definitions

    • CNVII: Cranial nerve that carries motor nerves to muscles of facial expression; parasympathetics to lacrimal, submandibular, and sublingual glands; and taste from anterior 2/3 of tongue

IMAGING ANATOMY

  • Overview

    • Mixed nerve: Motor, parasympathetic, and special sensory (taste)
    • 2 roots: Motor and sensory (nervus intermedius) roots - Nervus intermedius exits lateral brainstem between motor root of facial and vestibulocochlear nerves, hence its name
    • 3 nuclei and 4 segments: Intraaxial, cisternal, intratemporal, and extracranial (parotid)

  • Nuclei and Intraaxial Segment

    • 3 nuclei (1 motor, 2 sensory)
    • Motor nucleus of facial nerve - Located in ventrolateral pontine tegmentum - Efferent fibers loop dorsally around CNVI nucleus in floor of 4th ventricle, forming facial colliculus - Fibers then course anterolaterally to exit lateral brainstem at pontomedullary junction
    • Superior salivatory nucleus - Located lateral to CNVII motor nucleus in pons - Efferent parasympathetic fibers exit brainstem posterior to CNVII as nervus intermedius - To submandibular, sublingual, and lacrimal glands
    • Solitarius tract nucleus - Termination of taste sensation fibers from anterior 2/3 of tongue - Cell bodies of these fibers in geniculate ganglion - Fibers travel within nervus intermedius

  • Cisternal Segment

    • 2 roots in cisternal CNVII - Larger motor root anteriorly - Smaller sensory nervus intermedius posteriorly
    • Emerge from lateral brainstem at root exit zone in pontomedullary junction to enter cerebellopontine angle (CPA) cistern - CNVIII exits brainstem posterior to CNVII
    • 2 roots join together and pass anterolaterally through CPA cistern with CNVIII to internal auditory canal (IAC)

  • Intratemporal Segment

    • CNVII further divided in T-bone into 4 segments: IAC, labyrinthine, tympanic, and mastoid
    • IAC segment: Porus acusticus to IAC fundus; anterosuperior position above crista falciformis
    • Labyrinthine segment: Connects fundal CNVII to geniculate ganglion (anterior genu)
    • Tympanic segment: Connects anterior to posterior genu, passing under lateral semicircular canal
    • Mastoid segment: Inferiorly directed from posterior genu to stylomastoid foramen

  • Extracranial Segment

    • Main CNVII exits skull base through stylomastoid foramen to enter parotid space
    • Parotid CNVII passes lateral to retromandibular vein
    • Ramifies within parotid, passes anteriorly to innervate muscles of facial expression

  • CNVII Branches

    • Greater superficial petrosal nerve - Arises at geniculate ganglion, passes anteromedially, exits temporal bone via facial hiatus - Carries parasympathetic fibers to lacrimal gland
    • Stapedius nerve - Arises from high mastoid segment of CNVII - Provides motor innervation to stapedius muscle
    • Chorda tympani nerve - Arises from lower mastoid segment - Courses across middle ear to exit anterior T-bone - Carries taste fibers from anterior 2/3 of tongue - These fibers travel with lingual branch of mandibular division of trigeminal nerve
    • Terminal motor branches to muscles of facial expression - Superior to inferior: Temporal, zygomatic, buccal, mandibular, cervical

ANATOMY IMAGING ISSUES

  • Imaging Recommendations

    • Bone CT best for intratemporal segment of CNVII
    • MR for intraaxial, cisternal, IAC, and extracranial segments
    • Do not image routine Bell palsy!

  • Imaging Sweet Spots

    • Include brainstem, CPA cistern, IAC, T-bone, and parotid when MR completed for CNVII palsy

  • Imaging Pitfalls

    • Mild enhancement of labyrinthine segment, geniculate ganglion, and proximal tympanic segments of CNVII can be normal on postcontrast T1 MR - Secondary to circumneural arteriovenous plexus
    • Always check parotid in peripheral CNVII paralysis

  • Clinical Issues

    • Facial nerve paralysis can be central or peripheral - Central: Supranuclear injury resulting in paralysis of contralateral muscles of facial expression with forehead sparing - Peripheral: Injury to CNVII from brainstem nucleus peripherally, resulting in paralysis of all ipsilateral muscles of facial expression - If lesion proximal to geniculate ganglion, lacrimation, sound dampening, and taste affected - If CNVI involved, check pons for lesion - If CNVIII involved, check CPA-IAC for lesion - If lacrimation, sound dampening, and taste are variably affected, T-bone lesion possible - If lacrimation, sound dampening and taste are spared, extracranial CNVII implicated

ca024fe5-308b-4a45-965f-f5040eddf104

Images

Graphics

Axial graphic shows CNVII nuclei. Motor nucleus sends out its fibers to circle CNVI nucleus before reaching root exit zone at the pontomedullary junction. The superior salivatory nucleus sends parasympathetic secretomotor fibers to the lacrimal, submandibular, and sublingual glands. Solitary tract nucleus receives anterior 2/3 of tongue taste information. Axial graphic shows CNVII nuclei. Motor nucleus sends out its fibers to circle CNVI nucleus before reaching root exit zone at the pontomedullary junction. The superior salivatory nucleus sends parasympathetic secretomotor fibers to the lacrimal, submandibular, and sublingual glands. Solitary tract nucleus receives anterior 2/3 of tongue taste information.

Sagittal graphic depicts CNVII within the temporal bone. Motor fibers pass through the temporal bone, dropping the stapedius nerve to the stapedius muscle, then exit via the stylomastoid foramen to extracranial CNVII (entirely motor). Parasympathetic fibers from superior salivatory nucleus reach the lacrimal gland via the greater superficial petrosal nerve and submandibular-sublingual glands via the chorda tympanic nerve. The anterior 2/3 of tongue taste fibers come via the chorda tympani nerve. Sagittal graphic depicts CNVII within the temporal bone. Motor fibers pass through the temporal bone, dropping the stapedius nerve to the stapedius muscle, then exit via the stylomastoid foramen to extracranial CNVII (entirely motor). Parasympathetic fibers from superior salivatory nucleus reach the lacrimal gland via the greater superficial petrosal nerve and submandibular-sublingual glands via the chorda tympanic nerve. The anterior 2/3 of tongue taste fibers come via the chorda tympani nerve.

Sagittal graphic depicts extracranial motor branches of the facial nerve. Sagittal graphic depicts extracranial motor branches of the facial nerve.

Axial Bone CT

First of 6 axial bone CT of the left temporal bone presented from superior to inferior shows the labyrinthine segment of the facial nerve canal as a C-shaped structure arching anterolaterally over the top of the cochlea. First of 6 axial bone CT of the left temporal bone presented from superior to inferior shows the labyrinthine segment of the facial nerve canal as a C-shaped structure arching anterolaterally over the top of the cochlea.

In this image, the labyrinthine segment of CNVII canal terminates in the geniculate fossa. The facial nerve canal turns abruptly at the geniculate fossa (anterior genu). The tympanic segment arises from the geniculate fossa, coursing posterolaterally in the axial plane, running under the lateral semicircular canal before turning 90° inferiorly at the posterior genu to become the mastoid segment. In this image, the labyrinthine segment of CNVII canal terminates in the geniculate fossa. The facial nerve canal turns abruptly at the geniculate fossa (anterior genu). The tympanic segment arises from the geniculate fossa, coursing posterolaterally in the axial plane, running under the lateral semicircular canal before turning 90° inferiorly at the posterior genu to become the mastoid segment.

At the level of the oval window, the mastoid segment is visible deep to the facial nerve recess. Notice the more medial pyramidal eminence and sinus tympani. At the level of the oval window, the mastoid segment is visible deep to the facial nerve recess. Notice the more medial pyramidal eminence and sinus tympani.

Mastoid segment extends ~ 13 mm from the posterior genu to the stylomastoid foramen, coursing inferiorly within the posterior wall of the middle ear cavity. The mastoid segment is related anteriorly to the facial nerve recess and medially to the stapedius muscle within the pyramidal eminence on the posterior wall of the middle ear cavity. Mastoid segment extends ~ 13 mm from the posterior genu to the stylomastoid foramen, coursing inferiorly within the posterior wall of the middle ear cavity. The mastoid segment is related anteriorly to the facial nerve recess and medially to the stapedius muscle within the pyramidal eminence on the posterior wall of the middle ear cavity.

At the level of the basal turn of the cochlea, the mastoid segment of the facial nerve is still visible. Both the nerve to the stapedius muscle proximally and the chorda tympani distally branch off the mastoid segment (CNVII). At the level of the basal turn of the cochlea, the mastoid segment of the facial nerve is still visible. Both the nerve to the stapedius muscle proximally and the chorda tympani distally branch off the mastoid segment (CNVII).

Image at the level of the stylomastoid foramen is shown. Notice the "bell" of the stylomastoid foramen is just anteromedial to the mastoid tip. The mastoid tip protects the facial nerve from traumatic injury as it exits the skull base. Image at the level of the stylomastoid foramen is shown. Notice the "bell" of the stylomastoid foramen is just anteromedial to the mastoid tip. The mastoid tip protects the facial nerve from traumatic injury as it exits the skull base.

Coronal Bone CT

First of 6 coronal bone CT of the left temporal bone presented from posterior to anterior shows the lower mastoid segment of the facial nerve (CNVII) and stylomastoid foramen. First of 6 coronal bone CT of the left temporal bone presented from posterior to anterior shows the lower mastoid segment of the facial nerve (CNVII) and stylomastoid foramen.

At the level of the round window, the posterior genu of the facial nerve can be seen just lateral to the pyramidal eminence. Notice the sinus tympani is medial to the pyramidal eminence. At the level of the round window, the posterior genu of the facial nerve can be seen just lateral to the pyramidal eminence. Notice the sinus tympani is medial to the pyramidal eminence.

At the level of the oval window, the tympanic segment of the facial nerve can be seen coursing under the lateral semicircular canal. Notice the fine bony covering (thin white line) surrounding the facial nerve. Also note the location relative to the upper margin of the oval window. In patients with oval window atresia, the facial nerve is found near or within the oval window niche. At the level of the oval window, the tympanic segment of the facial nerve can be seen coursing under the lateral semicircular canal. Notice the fine bony covering (thin white line) surrounding the facial nerve. Also note the location relative to the upper margin of the oval window. In patients with oval window atresia, the facial nerve is found near or within the oval window niche.

At the level of the anterior margin of the oval window, the tympanic segment of the facial nerve can be seen under the lateral semicircular canal. Notice the fine bony covering (thin white line) surrounding the facial nerve is now not seen. The facial nerve canal bony covering in this area is normally incomplete. At the level of the anterior margin of the oval window, the tympanic segment of the facial nerve can be seen under the lateral semicircular canal. Notice the fine bony covering (thin white line) surrounding the facial nerve is now not seen. The facial nerve canal bony covering in this area is normally incomplete.

In the anterior middle ear cavity, the labyrinthine segment of the facial nerve can be seen exiting the internal auditory canal over the top of the cochlea. The anterior tympanic segment of the facial nerve is also visible. Do not confuse the muscle-tendon of the tensor tympani in the cochleariform process with the facial nerve. In the anterior middle ear cavity, the labyrinthine segment of the facial nerve can be seen exiting the internal auditory canal over the top of the cochlea. The anterior tympanic segment of the facial nerve is also visible. Do not confuse the muscle-tendon of the tensor tympani in the cochleariform process with the facial nerve.

In the most anterior portion of middle ear cavity (where both the carotid and the cochlea are visible), the geniculate ganglion is seen within the geniculate fossa as an ovoid structure just above the cochlea. In the most anterior portion of middle ear cavity (where both the carotid and the cochlea are visible), the geniculate ganglion is seen within the geniculate fossa as an ovoid structure just above the cochlea.

3T Axial T2 & T1 MR

First of 2 axial high-resolution T2 MR through the cerebellopontine angle cistern and internal auditory canal is shown. The facial nerve root exit zone is seen anterior to the vestibulocochlear nerve in the pontomedullary junction bilaterally. Notice the facial nerve maintains an anterior relationship with the vestibulocochlear nerve as it crosses through the cerebellopontine angle cistern. First of 2 axial high-resolution T2 MR through the cerebellopontine angle cistern and internal auditory canal is shown. The facial nerve root exit zone is seen anterior to the vestibulocochlear nerve in the pontomedullary junction bilaterally. Notice the facial nerve maintains an anterior relationship with the vestibulocochlear nerve as it crosses through the cerebellopontine angle cistern.

Image through the cephalad internal auditory canal on the patient's left shows the facial nerve anterior to the superior vestibular nerve throughout its internal auditory canal course. Image through the cephalad internal auditory canal on the patient's left shows the facial nerve anterior to the superior vestibular nerve throughout its internal auditory canal course.

Axial T1 MR at the level of the stylomastoid foramen shows the exiting low-signal facial nerve surrounded by high-signal fat in the "bell" of the stylomastoid foramen. If perineural parotid malignancy is present, the fat in this area is obscured. Axial T1 MR at the level of the stylomastoid foramen shows the exiting low-signal facial nerve surrounded by high-signal fat in the "bell" of the stylomastoid foramen. If perineural parotid malignancy is present, the fat in this area is obscured.

3T Oblique Sagittal T2 MR

First of 3 oblique sagittal T2 MR presented from lateral to medial shows normal fundal anatomy. The horizontal crista falciformis separates the fundus into the upper and lower portions. The facial nerve is anterosuperior, separated from the superior vestibular nerve by a vertical bony septum called the "Bill bar," which is not resolved. Below the falciform crest are the larger anterior cochlear nerve and posterior inferior vestibular nerve. First of 3 oblique sagittal T2 MR presented from lateral to medial shows normal fundal anatomy. The horizontal crista falciformis separates the fundus into the upper and lower portions. The facial nerve is anterosuperior, separated from the superior vestibular nerve by a vertical bony septum called the "Bill bar," which is not resolved. Below the falciform crest are the larger anterior cochlear nerve and posterior inferior vestibular nerve.

In the midinternal auditory canal, 4 nerves are clearly identified. The facial nerve is anterosuperior. In the midinternal auditory canal, 4 nerves are clearly identified. The facial nerve is anterosuperior.

This image through the porus acusticus reveals the characteristic ball in a catcher's mitt appearance of the facial and vestibulocochlear nerves. The facial nerve is the "ball" and the vestibulocochlear nerve is the "catcher's mitt." This image through the porus acusticus reveals the characteristic ball in a catcher's mitt appearance of the facial and vestibulocochlear nerves. The facial nerve is the "ball" and the vestibulocochlear nerve is the "catcher's mitt."

3T T2-SPACE MR

First of a series of 3 axial slices of a T2 sampling perfection with application-optimized contrasts by using flip angle evolution (T2-SPACE) MR showing the facial nerve. First of a series of 3 axial slices of a T2 sampling perfection with application-optimized contrasts by using flip angle evolution (T2-SPACE) MR showing the facial nerve.

Second in the series shows a more superior axial T2-SPACE MR slice through the facial nerve. Second in the series shows a more superior axial T2-SPACE MR slice through the facial nerve.

Third in the series shows a detailed view of an axial T2-SPACE MR slice through the facial nerve. The facial nerve was manually segmented and rendered in 3D in pink. The cochlear and vestibular nerves are also partially visible in green and orange, respectively. Third in the series shows a detailed view of an axial T2-SPACE MR slice through the facial nerve. The facial nerve was manually segmented and rendered in 3D in pink. The cochlear and vestibular nerves are also partially visible in green and orange, respectively.

3T MR

A 3D surface rendering from T2-SPACE MR of the facial (CNVII) and vestibulocochlear nerve (CNVIII) is shown. The facial nerve was manually segmented and rendered in 3D in pink. The cochlear and vestibular nerves are also partially visible in green and orange, respectively. A 3D surface rendering from T2-SPACE MR of the facial (CNVII) and vestibulocochlear nerve (CNVIII) is shown. The facial nerve was manually segmented and rendered in 3D in pink. The cochlear and vestibular nerves are also partially visible in green and orange, respectively.

First of 2 axial sections of a diffusion tensor imaging (DTI) dataset shows the facial nerve along with white matter pathways. The image is colored to indicate orientation, where left-right fibers are colored in red, anterior-posterior fibers are colored in green, and inferior-superior fibers are colored in blue. Note: The facial nerve (CNVII) cannot be visibly discerned from the vestibulocochlear nerve (CNVIII) at this resolution. First of 2 axial sections of a diffusion tensor imaging (DTI) dataset shows the facial nerve along with white matter pathways. The image is colored to indicate orientation, where left-right fibers are colored in red, anterior-posterior fibers are colored in green, and inferior-superior fibers are colored in blue. Note: The facial nerve (CNVII) cannot be visibly discerned from the vestibulocochlear nerve (CNVIII) at this resolution.

Second of 2 axial sections of a DTI dataset showing the facial nerve along with white matter pathways is shown. The facial nerve (CNVII) was modeled using diffusion tractography (orange). Note: The facial nerve (CNVII) cannot be visibly discerned from the vestibulocochlear nerve (CNVIII) at this resolution. Second of 2 axial sections of a DTI dataset showing the facial nerve along with white matter pathways is shown. The facial nerve (CNVII) was modeled using diffusion tractography (orange). Note: The facial nerve (CNVII) cannot be visibly discerned from the vestibulocochlear nerve (CNVIII) at this resolution.

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