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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
CNVII (Facial Nerve) 98cb2d45-e64c-4295-9662-3470cd46513a
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1fa14dfd-71ea-4960-908e-e720313bc63a Santhosh Gaddikeri, MD
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94f835c8-fa13-4e8a-995b-53048e6b0605 Philip R. Chapman, MD
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Head and Neck head-and-neck ed24ed8c-5d57-4629-879b-447b82d2973d
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Anatomy anatomy 678bc99d-d43e-45e6-9c8d-9fa5a7648616
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Cranial Nerves cranial-nerves 5cb153f5-b8a6-4321-a37d-ac4e2a31be47
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CNVII (Facial Nerve) cnvii-facial-nerve null
Head and Neck 0baca093-e8fa-4711-9ecc-05167315d50b 1e66f9a4-6069-4b31-b464-8a6b37d40f11 39 12/06/23 CNVII (Facial Nerve) Head and Neck, Anatomy, Cranial Nerves, CNVII (Facial Nerve) CNVII (Facial Nerve) | STATdx CNVII (Facial Nerve) ANATOMY
Head and Neck
Anatomy
Cranial Nerves
CNVII (Facial Nerve)

title: "CNVII (Facial Nerve)" docid: "98cb2d45-e64c-4295-9662-3470cd46513a" authors:

  • key: "1fa14dfd-71ea-4960-908e-e720313bc63a" value: "Santhosh Gaddikeri, MD"
  • key: "94f835c8-fa13-4e8a-995b-53048e6b0605" value: "Philip R. Chapman, MD" breadcrumbs:
  • name: "Head and Neck" slug: "head-and-neck" treeNodeId: "ed24ed8c-5d57-4629-879b-447b82d2973d"
  • name: "Anatomy" slug: "anatomy" treeNodeId: "678bc99d-d43e-45e6-9c8d-9fa5a7648616"
  • name: "Cranial Nerves" slug: "cranial-nerves" treeNodeId: "5cb153f5-b8a6-4321-a37d-ac4e2a31be47"
  • name: "CNVII (Facial Nerve)" slug: "cnvii-facial-nerve" treeNodeId: null category: "Head and Neck" cmeTopicId: "0baca093-e8fa-4711-9ecc-05167315d50b" documentVersionId: "1e66f9a4-6069-4b31-b464-8a6b37d40f11" imageCount: 39 lastUpdated: "12/06/23" pageDescription: "CNVII (Facial Nerve)" pageKeywords: "Head and Neck, Anatomy, Cranial Nerves, CNVII (Facial Nerve)" pageTitle: "CNVII (Facial Nerve) | STATdx" enhancedTitle: "CNVII (Facial Nerve)" type: "ANATOMY" breadcrumbs:
  • "Head and Neck"
  • "Anatomy"
  • "Cranial Nerves"
  • "CNVII (Facial Nerve)"

TERMINOLOGY

  • Abbreviations

    • Facial nerve (CNVII)

  • Synonyms

    • 7th cranial nerve

  • Definitions

    • CNVII: Cranial nerve carrying motor nerves to muscles of facial expression; parasympathetics to lacrimal, submandibular, & 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 CNVII and CNVIII, hence its name
    • 3 nuclei and 4 segments: Intraaxial, cisternal, intratemporal, and extracranial (parotid)
    • Blood supply from petrosal branch of middle meningeal artery & stylomastoid branch of posterior auricular artery

  • 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 - 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

    • Further divided in temporal bone into 4 segments: IAC, labyrinthine, tympanic, & 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 - Joined by deep petrosal nerve (sympathetic fibers) in foramen lacerum to form vidian nerve
    • Nerve to stapedius - Arises from high mastoid segment of CNVII behind pyramidal eminence - Provides motor innervation to stapedius muscle
    • Chorda tympani - Arises from lower mastoid segment - Courses across middle ear to exit anterior temporal bone - Carries taste fibers from anterior 2/3 of tongue - Fibers travel with lingual branch of mandibular division of trigeminal nerve - Carries parasympathetic fibers to submandibular & sublingual glands via submandibular ganglion
    • Terminal motor branches to muscles of facial expression - Superior to inferior: Temporal, zygomatic, buccal, mandibular, cervical

ANATOMY IMAGING ISSUES

  • Imaging Recommendations

    • High-resolution bone CT best for intratemporal CNVII
    • MR for intraaxial, cisternal, IAC, and extracranial segments - 3D heavily T2 sequence, thin-section axial and coronal T2, precontrast and postcontrast fat-saturated T1
    • Include brainstem, CPA cistern, IAC, temporal bone, and parotidwhen MR completed for CNVII palsy
    • Do not image typical Bell palsy

  • Imaging Pitfalls

    • Enhancement of geniculate ganglion, tympanic & mastoid segments of CNVII normal on postcontrast T1 MR; can be asymmetric intensity of enhancement on right & left - Secondary to circumneural arteriovenous plexus
    • Cisternal, IAC, labyrinthine, and parotid segments do not normally enhance on MR - Faint enhancement may be seen depending on MR scanner, sequence, & type of contrast used - Be familiar with normal images in different institutions
    • Always check parotid in peripheral CNVII paralysis

  • Clinical Issues

    • Facial nerve paralysis can be central or peripheral - Central: Supranuclear injury; 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 - Lesion proximal to geniculate ganglion; lacrimation, sound dampening and taste are affected - CNVI involved; check pons for lesion - CNVIII involved; check CPA-IAC for lesion - Lacrimation, sound dampening, and taste are variably affected; temporal bone lesion possible - Lacrimation, sound dampening, and taste are spared; extracranial CNVII implicated

965f30b5-41e0-4767-82e6-813a492e4281

Images

Graphics

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

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

Sagittal graphic depicts CNVII within the temporal bone. Motor fibers pass through the temporal bone, dropping stapedius nerve to stapedius muscle, then exits via the stylomastoid foramen to the extracranial CNVII (entirely motor). Parasympathetic fibers from the superior salivatory nucleus reach the lacrimal gland via the greater superficial petrosal nerve and the 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 stapedius nerve to stapedius muscle, then exits via the stylomastoid foramen to the extracranial CNVII (entirely motor). Parasympathetic fibers from the superior salivatory nucleus reach the lacrimal gland via the greater superficial petrosal nerve and the 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 the extracranial motor branches of CNVII. Sagittal graphic depicts the extracranial motor branches of CNVII.

Axial Bone CT

First of 5 high-resolution NECT bone window images of the right temporal bone from superior to inferior demonstrates the CNVII canal for the labyrinthine segment coursing anterolaterally from the fundus of the internal auditory canal (IAC) to the geniculate fossa. The labyrinthine segment is the shortest and narrowest segment. First of 5 high-resolution NECT bone window images of the right temporal bone from superior to inferior demonstrates the CNVII canal for the labyrinthine segment coursing anterolaterally from the fundus of the internal auditory canal (IAC) to the geniculate fossa. The labyrinthine segment is the shortest and narrowest segment.

This image demonstrates the geniculate fossa, which lodges the geniculate ganglion. The greater (superficial) petrosal nerve (not shown) arises here and travels anteromedially toward the foramen lacerum. This image demonstrates the geniculate fossa, which lodges the geniculate ganglion. The greater (superficial) petrosal nerve (not shown) arises here and travels anteromedially toward the foramen lacerum.

This image demonstrates the tympanic segment of CNVII arising from the geniculate ganglion and traversing posteriorly and laterally to take a 2nd turn downward, forming the posterior genu (not shown). This image demonstrates the tympanic segment of CNVII arising from the geniculate ganglion and traversing posteriorly and laterally to take a 2nd turn downward, forming the posterior genu (not shown).

This image demonstrates the high mastoid segment of CNVII canal posteriorly, which then descends toward the stylomastoid foramen. Nerve to stapedius arises at this level. This image demonstrates the high mastoid segment of CNVII canal posteriorly, which then descends toward the stylomastoid foramen. Nerve to stapedius arises at this level.

This image demonstrates the midmastoid segment of CNVII with adjacent chorda tympani. This image demonstrates the midmastoid segment of CNVII with adjacent chorda tympani.

Axial soft tissue window NECT through the skull base demonstrates bilateral fat-containing stylomastoid foramen. CNVII exits from bone canal into the parotid space through this foramen. Axial soft tissue window NECT through the skull base demonstrates bilateral fat-containing stylomastoid foramen. CNVII exits from bone canal into the parotid space through this foramen.

Coronal Bone CT

First of 6 coronal reformatted high-resolution NECT bone window images show the labyrinthine segment of CNVII canal arising from the superior aspect of the fundus of the IAC. First of 6 coronal reformatted high-resolution NECT bone window images show the labyrinthine segment of CNVII canal arising from the superior aspect of the fundus of the IAC.

This image shows the snake eye appearance of labyrinthine and tympanic segments coursing adjacent to each other. The labyrinthine segment courses posteriorly toward the geniculate fossa, and the tympanic segment courses anteriorly away from the geniculate fossa. This image shows the snake eye appearance of labyrinthine and tympanic segments coursing adjacent to each other. The labyrinthine segment courses posteriorly toward the geniculate fossa, and the tympanic segment courses anteriorly away from the geniculate fossa.

This image shows the geniculate fossa, which lodges the geniculate ganglion. This image shows the geniculate fossa, which lodges the geniculate ganglion.

This image shows the lateral semicircular canal, the tympanic segment of CNVII canal, and oval window from superior to inferior along the medial wall of the middle ear cavity. This image shows the lateral semicircular canal, the tympanic segment of CNVII canal, and oval window from superior to inferior along the medial wall of the middle ear cavity.

This image shows the descending mastoid segment of the CNVII canal. The chorda tympani leaves the CNVII canal 6 mm above the stylomastoid foramen and enters the middle ear cavity through the posterior canaliculus (not shown). This image shows the descending mastoid segment of the CNVII canal. The chorda tympani leaves the CNVII canal 6 mm above the stylomastoid foramen and enters the middle ear cavity through the posterior canaliculus (not shown).

This image shows the distal part of the CNVII mastoid segment exiting through the stylomastoid foramen into the parotid space. This image shows the distal part of the CNVII mastoid segment exiting through the stylomastoid foramen into the parotid space.

Axial T2 MR

First of 2 axial 3D T2 SPACE MR images through the left IAC shows CNVII arising from the lateral pontomedullary junction at the root exit zone. It then traverses the cerebellopontine angle cistern and enters the IAC through the porus acusticus. Note that posterior to it is the superior vestibular nerve. First of 2 axial 3D T2 SPACE MR images through the left IAC shows CNVII arising from the lateral pontomedullary junction at the root exit zone. It then traverses the cerebellopontine angle cistern and enters the IAC through the porus acusticus. Note that posterior to it is the superior vestibular nerve.

This image shows the IAC and labyrinthine segments of CNVII in the anterosuperior quadrant. This image shows the IAC and labyrinthine segments of CNVII in the anterosuperior quadrant.

Axial 3D T2 SPACE MR through the skull base at the level of stylomastoid foramina shows bilateral facial nerve mastoid segment exiting the bony canal and entering the parotid space. Note the fat surrounding the facial nerves bilaterally at this level. Axial 3D T2 SPACE MR through the skull base at the level of stylomastoid foramina shows bilateral facial nerve mastoid segment exiting the bony canal and entering the parotid space. Note the fat surrounding the facial nerves bilaterally at this level.

Oblique Sagittal T2 MR

First of 3 sagittal oblique MR images of the IAC from medial to lateral is shown. This image through the porus acusticus shows the anteriorly traversing facial nerve trunk, and immediately posterior to it is the vestibulocochlear nerve, both entering the IAC. First of 3 sagittal oblique MR images of the IAC from medial to lateral is shown. This image through the porus acusticus shows the anteriorly traversing facial nerve trunk, and immediately posterior to it is the vestibulocochlear nerve, both entering the IAC.

This image through the middle of the IAC shows the appearance of a ball in the catcher's mitt where the ball is CNVII and the catcher's mitt is formed by the vestibulocochlear nerve complex. This image through the middle of the IAC shows the appearance of a ball in the catcher's mitt where the ball is CNVII and the catcher's mitt is formed by the vestibulocochlear nerve complex.

This image through the fundus of the IAC shows CNVII in the anterosuperior quadrant above the crista falciformis. Note the anteroinferiorly located cochlear nerve, posterosuperiorly located superior vestibular nerve, and posteroinferiorly located inferior vestibular nerve. This image through the fundus of the IAC shows CNVII in the anterosuperior quadrant above the crista falciformis. Note the anteroinferiorly located cochlear nerve, posterosuperiorly located superior vestibular nerve, and posteroinferiorly located inferior vestibular nerve.

Additional Images

First of 6 axial bone CT images 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 images 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 axial plane, running under the lateral semicircular canal before turning 90 degrees 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 axial plane, running under the lateral semicircular canal before turning 90 degrees 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. 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. 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 stapedius muscle proximally and chorda tympani distally branch off the mastoid segment of 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 stapedius muscle proximally and chorda tympani distally branch off the mastoid segment of 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.

First of 6 coronal bone CT images of the left temporal bone presented from posterior to anterior shows the lower mastoid segment of CNVII and stylomastoid foramen. First of 6 coronal bone CT images of the left temporal bone presented from posterior to anterior shows the lower mastoid segment of 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 CVII 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 CVII 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 CNVII 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 CNVII 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.

First of 2 axial high-resolution T2 MR images 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 images 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 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 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.

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

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

This image through the porus acusticus reveals the characteristic ball in 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 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."

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