INTRATEMPORAL COURSE OF FACIAL NERVE:
From internal acoustic meatus to stylomastoid foramen.
A) MEATAL SEGMENT: a. 8-10 mm.
b. Within internal acoustic meatus.
B) LABYRINTH SEGMENT: a. 4 mm.
b. From fundus of meatus to geniculate ganglion, where nerves takes a turn posteriorly forming “Genu”.
C) TYMPANIC OR HORIZONTAL SEGMENT: a. 11 mm.
b. From Geniculate ganglion to just above the pyramidal eminence.
c. Lies above oval window & below lateral semicircular canal.
D) MASTOID OR VERTICAL SEGMENT: a. 13 mm.
b. From Pyramid to Stylomastoid foramen.
c. Between Tympanic & mastoid segments is the 2nd Genu of nerve.
DESCRIBE THE RELEVENT TOPO DIAGNOSTIC TESTS:
These tests are useful in finding the site of lesion in paralysis of LMN.
A strip of filter paper is hooked in the lower fornix of each eye & amount of wetting of strip measured.
Decrease Lacrimation- Lesion proximal to geniculate ganglion as secretomotor fibres to lacrimal gland leave at the geniculate ganglion via greater superficial petrosal nerve.
Tested by tympanometry.
Impairment of taste- lesion above the Chorda Tympani.
Polythene tubes are passed into both Whartan Ducts & drops of saliva counted during one minute period.
Decrease Salivation- Injury above Chorda Tympani.
© 2017 Medshale - All rights reserved