Anatomy of 7th nerve

Roots:
Motor - large, anterior
Sensory - smaller, N intermedius, posterior
Cisternal segment:
Both roots join and pass anterolaterally through CPA cistern
Intratemporal segment:
IAC: anterosuperior in position, superior to crista falciformis. Superior vestibular nerve is posteior to it. Cochlear nerve is inferior to it. Inferior vestibular nerve is posteroinferior to it.
Labyrinthine: Up to geniculate ganglion, superior to cochlea. Stops at anterior genu
Tympanic: Starts at anterior genu. Includes geniculate ganglion. Ends at posterior genu. passes inferior to L-SCC
Mastoid: up to stylomastoid foramen. Anteriorly facial nerve recess; medially stepedius, pyramidal eminence and sinus tympani (sinus tympani is medial to pyramidal eminence)
Extracranial:
Enters parotid, lateral to RMV

ANATOMIC LOCALIZATION BASED ON CLINICAL SYMPTOMS:
1. Paralysis of muscles of facial expression with forehead sparing: supranuclear, i.e. central
2. Paralysis of muscles of facial expression with forehead involvement: infranuclear, i.e from brain stem below
a. involvement of 6th CN - pons
b. involvement of 8th CN - CAP, IAC
c. involvement of lacrimation, sound and taste - proximal to geniculate ganglion
d. variable involvement of lacrimation, sound and taste - intratemporal
e. sparing of lacrimation, sound and taste - extracranial
b.