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Facial Nerve (CNVII)

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• 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

• 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)

• 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)

• 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

• 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

• 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

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Tags: Imaging Anatomy Brain and Spine

Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off