ABSTRACT
TIP: Ipsilateral supranuclear lesions give contralateral facial paralysis but maintain frontalis function.
2. Intratemporal • Facial nerve enters the internal auditory canal and travels with the acoustic and vestibular
nerves for approximately 8-10 mm. • Facial nerve then enters the fallopian canal by itself, where it travels for 30 mm. • Meatal foramen is the narrowest portion of the fallopian canal, measuring 0.68 mm in
diameter. • Fallopian canal has three segments (Fig. 42-1). 1. Labyrinthine segment 5-6 mm long, from entrance of the fallopian canal to the geniculate ganglion Geniculate ganglion contains the nerve cell bodies of taste and sensation. Narrowest segment: 1.42 mm diameter on average, nerve occupies 83% of available
space Greater petrosal nerve: First branch off geniculate ganglion, supplies parasympathetic
nerves for lacrimal gland and sensory taste fibers from the palate Junction of labyrinthine and tympanic segments formed by an acute angle: Shearing
occurs commonly 2. Tympanic segment 8-11 mm long, from geniculate ganglion to bend at lateral semicircular canal
3. Mastoid segment 9-12 mm long, from bend at lateral semicircular canal to stylomastoid foramen Widest cross-sectional area Three nerve branches
Nerve to stapedius: Motor function for stapedius muscle, allows dampening of loud sounds; cell bodies of this motor nerve not located in facial nucleus, therefore not affected by Möbius’ syndrome
Sensory branch to external auditory canal: Hitselberger’s sign: Hypesthesia of external auditory canal
Chorda tympani: Final intratemporal branch, joins lingual nerve to provide parasympathetic innervation to submandibular and sublingual glands; special sensory afferents from anterior two thirds of tongue
TIP: In children, the ratio of facial nerve diameter to fallopian canal diameter is less than in adults, which decreases the likelihood of facial nerve entrapment.
