This document discusses various tests used to evaluate facial nerve function including physical examination, House Brackmann grading scale, topodiagnostic tests, and electrodiagnostic tests. Physical examination evaluates features like facial asymmetry, eyebrow position, and ability to close eyes. Electrodiagnostic tests like electroneuronography, electromyography, and acoustic reflex testing can help localize facial nerve lesions and assess prognosis for recovery. Together these evaluation methods provide information on the severity and location of facial nerve damage.

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