TELLS ABOUT VARIOUS TESTS OF FACIAL NERVE

1. DR.RAM SHANKAR RENGANATHAN
Tests of facial nerve
function

2. Facial Nerve Test
Detect facial nerve lesion
Measure severity
Localise site of lesion
Assess prognosis for recovery
Assist in decisions
Detect and avoid surgical injury*

3. PHYSICAL
EXAMINATION
 Facial assymetry*
 Eye brow drop
 Loss of forehead *and nasolabial fold
 Uncontrolled tears
 Inability to close the eyes*
 Drooling of corner of mouth
 Deviation of angle of mouth to opposite
side*

4. HOUSE BRACKMANN
GRADING

5. TOPODIAGNOSTIC
TESTS
 Lesion below the point at which particular
branch leave the facial nerve trunk will
spare the function subserved by that
branch
 Detect only most proximal lesions
 Do not give information about precise
level of lesions

6. FACIAL NERVE
COURSE

7. LACHRYMAL
FUNCTION
 Schirmer test
 Abnormal if affected side show less than
50% lachrymation compared to normal
side
or
 Sum of the length of wetted filter paper
for both eyes is <25mm
 Modified schirmer test?

8. STAPEDIAL REFLEX
 ABSENT REFLEX OR REFLEX LAST
LESS THAN ½ OF AMPLITUDE OF
NORMAL SIDE IS ABNORMAL
 USEFUL TO PREDICT RECOVERY
 +VE REFLEX <2 WEEKS OF INJURY
FULL RECOVERY OF NERVE WITHIN
12 WEEKS

9. TASTE FUNCTION
 Using pellets with Nacl or
electrogustometry
 Two sides of tongue has similar
threshold electric stimulation –normal
 Abnormal EGM response-no response
on affected side or threshold difference
is >20dB uA

10. SALVARY FLOW TEST
 <45% flow compared to normal side on
using 6%citric acid is abnormal
 <25%flow compared to normal side is
indication for surgery
 Submandibular scintigraphy-peak count
density,washout ratio<0.8 –incomplete
recovery in long term
 Submandibular saliva pH <6.1 -poor
recovery

11. ELECTRODIAGNOSTIC
TESTS
 Apply electric stimulation and measure
electromyographic response
 Identify patients with degeneration which is
an indication for decompression surgery

12. NERVE EXCITABILITY
TEST
 Difference of 2 to 3.5 mA in threshold
between both sides-reliable sign of
severe degeneration
 Increasing pulses of electrical
stimulation given

13. MAXIMUM
STIMULATION
TEST
 Supramaximal stimulus applied on
unaffected side until no further increase
in response is obtained and same
amount of stimuli applied to affected
side and response is measured as
0%,25%,50%,100%
 No response is an indication for
decompression

14. ELECTRONEURONOGRA
PHY
 Same as nerve excitability test but here
1 electrode at stylomastoid foramen and
other elctrode at nasolabial groove
 Normal response-difference in amplitude
between 2 sides is within 3%
 Quantify % of fibres degenerated
 Even if facial movement is normal and
ENoG is abnormal degeneration is
present

15. ELECTROMYOGRAPH
Y
 Measure spontaneous and voluntary
muscle potentials induced into muscle
 Active –stimulus applied and cMAP
measured
 Passive-spontaneous cMAP measured
 Used for intraoperative facial nerve
monitoring
 Most accurate to detect defective
healing

16. ACOUSTIC REFLEX
EVOKED
POTENTIALS
 Sound stimus applied and potentials
recorded in scalp electrodes
 Impulses after 12-15ms latency is d/t
facial motor pathway activation
 Persist even after anaesthesia.
 Intraop facial nerve monitoring

17. ANTIDROMIC
POTENTIALS
 Orthodromic potentials-towards muscle
 Antidromic potential-towards cell body
 Useful in acute setting

 Intraop facial nerve monitoring

18. BLINK REFLEX
 Electrical or mechanical stimulation of
supraorbital br of trigeminal nerve elicits
reflex contraction of orbicularis oculi
 Intra op facial nerve monitoring

19. MAGNETIC
STIMULATION
 Transcranial magnetic field causes
electrical stimulation of facial nerve at
IAM if temporoparietal area is stimulated

20. TRANSCRANIAL
EXCITATION OF FACIAL
MOTOR CORTEX
 Electrodes placed at c/l facial motor cortex
and response measured at muscle supplied
by it as MEP.
 Intraop facial nerve monitoring
 Entire facial nerve tract is tested

21. THANK YOU