clinically how the function of facial nerve is tested

1. Dr Tasnia Mahmud
Trainee in Otolaryngology
CMH, Dhaka
TESTS FOR FACIAL NERVE

2. TOPOGNOSTICTESTING
1. Schirmer test for lacrimation (GSPN)
2. Stapedial reflex test (Stapedial branch)
3. Taste testing (Chorda tympani nerve)
4. Salivary flow rates & pH (Chorda tympani)
ELECTROPHYSIOLOGICTESTS
Nerve excitability test (NET)
Electromyography(EMG)
Maximal stimulation test (MST)
Electroneuronography (ENoG)
Testing of Facial Nerve

3. Topographic Diagnosis
To determine the anatomical level of a peripheral lesion
Lacrimation Geniculate ganglion
Stapedius reflex motor nerve of stapedius muscle
Taste chorda tympani

4. Topodiagnostic tests

5. Schirmer'sTest

6. Schirmer's Test
Geniculate ganglion & petrosal nerve function test
Schirmer’s test +ve when
Affected side shows less than half the amount of lacrimation seen
on the normal side
Sum of the lengths of wetted filter paper for both eyes less than 25
mm
Lesion at or proximal to the geniculate ganglion

7. Stapedius reflex
Nerve to stapedius muscle test
Impedence audiometry can record the presence or absence
of stapedius muscle contraction to sound stimuli 70 to 100 db
above hearing threshold
An absence reflex or a reflex less than half the amplitude is
due to a lesion proximal to stapedius nerve

9. Stapedial Reflex

10. Taste (Electrogustometry)
Chorda tympani
nerve test
Tongue is
stimulated
electrically to
produce a metallic
taste and the two
sides are
compared

11. Electrogustometry
Normal : difference
< 20 uAmp
(thresholds differing
by more than 25%=
abnormal)
Total lack of
Chorda tympani :
No response at 300
uAmp
Disadvantage :
False +ve in acute
phase of Bell’s palsy

12. Salivary Flow Test
 Chorda tympani
 Warthins ducts are cannulated and salivary flow is
measured over time following a gustatory stimulus
 65% citric acid on anterior part of tongue
 <25% considered abnormal

13. Salivary flow test

14. ThankYou