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DR.RAM SHANKAR RENGANATHAN
Tests of facial nerve
function
Facial Nerve Test
Detect facial nerve lesion
Measure severity
Localise site of lesion
Assess prognosis for recovery
A...
PHYSICAL
EXAMINATION
 Facial assymetry*
 Eye brow drop
 Loss of forehead *and nasolabial fold
 Uncontrolled tears
 In...
HOUSE BRACKMANN
GRADING
TOPODIAGNOSTIC
TESTS
 Lesion below the point at which particular
branch leave the facial nerve trunk will
spare the funct...
FACIAL NERVE
COURSE
LACHRYMAL
FUNCTION
 Schirmer test
 Abnormal if affected side show less than
50% lachrymation compared to normal
side
or
...
STAPEDIAL REFLEX
 ABSENT REFLEX OR REFLEX LAST
LESS THAN ½ OF AMPLITUDE OF
NORMAL SIDE IS ABNORMAL
 USEFUL TO PREDICT RE...
TASTE FUNCTION
 Using pellets with Nacl or
electrogustometry
 Two sides of tongue has similar
threshold electric stimula...
SALVARY FLOW TEST
 <45% flow compared to normal side on
using 6%citric acid is abnormal
 <25%flow compared to normal sid...
ELECTRODIAGNOSTIC
TESTS
 Apply electric stimulation and measure
electromyographic response
 Identify patients with degen...
NERVE EXCITABILITY
TEST
 Difference of 2 to 3.5 mA in threshold
between both sides-reliable sign of
severe degeneration
...
MAXIMUM
STIMULATION
TEST
 Supramaximal stimulus applied on
unaffected side until no further increase
in response is obtai...
ELECTRONEURONOGRA
PHY
 Same as nerve excitability test but here
1 electrode at stylomastoid foramen and
other elctrode at...
ELECTROMYOGRAPH
Y
 Measure spontaneous and voluntary
muscle potentials induced into muscle
 Active –stimulus applied and...
ACOUSTIC REFLEX
EVOKED
POTENTIALS
 Sound stimus applied and potentials
recorded in scalp electrodes
 Impulses after 12-1...
ANTIDROMIC
POTENTIALS
 Orthodromic potentials-towards muscle
 Antidromic potential-towards cell body
 Useful in acute s...
BLINK REFLEX
 Electrical or mechanical stimulation of
supraorbital br of trigeminal nerve elicits
reflex contraction of o...
MAGNETIC
STIMULATION
 Transcranial magnetic field causes
electrical stimulation of facial nerve at
IAM if temporoparietal...
TRANSCRANIAL
EXCITATION OF FACIAL
MOTOR CORTEX
 Electrodes placed at c/l facial motor cortex
and response measured at mus...
THANK YOU
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Tests of facial nerve

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TELLS ABOUT VARIOUS TESTS OF FACIAL NERVE

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Tests of facial nerve

  1. 1. DR.RAM SHANKAR RENGANATHAN Tests of facial nerve function
  2. 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. 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. 4. HOUSE BRACKMANN GRADING
  5. 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. 6. FACIAL NERVE COURSE
  7. 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. 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. 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. 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. 11. ELECTRODIAGNOSTIC TESTS  Apply electric stimulation and measure electromyographic response  Identify patients with degeneration which is an indication for decompression surgery
  12. 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. 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. 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. 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. 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. 17. ANTIDROMIC POTENTIALS  Orthodromic potentials-towards muscle  Antidromic potential-towards cell body  Useful in acute setting   Intraop facial nerve monitoring
  18. 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. 19. MAGNETIC STIMULATION  Transcranial magnetic field causes electrical stimulation of facial nerve at IAM if temporoparietal area is stimulated
  20. 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. 21. THANK YOU

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