This PowerPoint is about about two audiometric tests namely bekesy audiometry and impedance audiometry and also about the special hearing tests.

1. ASSESSMENT OF HEARING
CHOYTOO Shiksha
ENT
29.02.16
SSR Medical ollege, Mauritius

2. AUDIOMETRIC TESTS (condt.)
• Bekesy audiometry
• Impedance audiometry

3. BEKESY AUDIOMETRY
• Self recording audiometry
• various pure tones frequencies automatically
move from low to high while the patient control
the intensity through a button
• Two tracings are obtained- one with continuous
tone and the other with pulsed tone
• Helps to differentiate
– Cochlear from retrocochlear HL
– Organic from functional HL

4. • Various types of tracings are obtained
– Type I: normal hearing or CHL
– Type II: cochlear loss
– Type III: retrocochlear or neural lesion
– Type IV: retrocochlear or neural lesion
– Type V: non organic hearing loss
• Seldom performed these days

6. IMPEDANCE AUDIOMETRY
• Widely used test
• Consists of
– Tympanomety
– Acoustic reflex measurement

7. TYMPANOMETRY
• Of all the sounds that strikes the TM, some sound energy is
absorbed while others are reflected.
• Stiff tympanic membrane will reflect more sound energy
that compliant one
• By changing the pressure in EAC, and then measuring the
reflected sound energy, it is possible to find out the degree
of compliance or stiffness of the Tympanossicular system
• Thus we can get an idea about the health status of middle
ear
• Tympanometry has also been used to find the fx of ET in
cases of intact or perforated TM

8. Type A Normal tympanogram
Type As Compliance is lower at ambient pressure
-otosclerosis , malleus fixation
Type AD Compliance is high at ambient pressure
-ossicular discontinuity or thin and lax
TM
Type B No change in compliance at ambient
pressure.
- Fluid in middle ear or thick TM
membrane
Type C Maximum compliance at negative
pressure
- Retracted TM or some fluid in middle
ear

9. ACOUSTIC REFLEX MEASUREMENTS
• Based on the fact that a loud sound 70-100dB
above the threshold of hearing of a particular
ear causes bilateral contraction of the
stapedial muscles which can be detected on
tympanogram
• Tone can be delivered to one ear and the
reflex can be picked from same or
contralateral ear.

10. • Useful in several ways:
– Test hearing in infants and young child (objective
method)
– To find malingerers (feigns total deafness and does
not give any response to pure tone audiometry
but shows positive stapedial reflex)
– Detect VIII th nerve lesions
– Detect facial nerve lesions
– Detect brainstem lesions

11. SPECIAL TESTS FOR HEARING
• Recruitment
• SISI test
• Evoked response audiometry
• Auditory steady state response
• Otoacoustic emissions
• Central auditory tests

12. RECRUITMENT
• Phenomenon of abnormal growth of loudness
• Ear which does not hear low intensity sound begin to hear
greater intensity sound as loud
• Patient with recruitment – poor candidate for hearing loss
• Recruitment is seen in cochlear lesions
• Helps to differentiate a cochlear from retrocochlear
sensorineural hearing loss
• Alternate binaural balance loudness test-detect
recruitment in unilateral cases

13. SHORT INCREMENT SENSITIVITY INDEX
(SISI)
• Patients with cochlear lesions distinguish smaller
changes in intensity of pure tone better that normal
person and those with conductive or retrocochlear
pathology
• In this test, continuous tone is presented 20dB above
the threshold and sustained for about 2 min
• Every 5s, tone is increased by 1 dB and 20 such blings
are presented
• Patient indicates the bling heard

14. • SISI scores:
– CHL 15 %
– Cochlear deafness 70-100%
– Nerve deafness 0-20 %

15. THRESHOLD TONE DECAY TEST
• Measure of nerve fatigue
• Use to detect retrocochlear lesions
• Normally, a person can hear a tone continuously for
60s
• In nerve fatigue, the person stops hearing earlier
• The result of the test is expressed as number of dB of
decay
• A decay of > 25 dB :diagnostic of retrocochlear lesion

16. EVOKED RESPONSE AUDIOMETRY
• Objective test
• Measure electrical activity in the auditory
pathways in response to auditory stimuli
• Requires special equipment with an averaging
computer
• Two components of evoked electric response
have gained clinical acceptance
– Electrocochleography
– Auditory brainstem response

17. ELECTROCOCHLEOGRAPHY
• Measures electrical potentials arising in the cochlea
and CN VIII th nerve in response to auditory stimuli
within first 5ms
• Response is in the form of 3 phenomenon
– Cochlear microphonics
– Summating potentials
– AP of CN VIII th nerve
• Recording electrode- thin needle passed through TM
onto the promontory
• Done under LA in adults ( apprehensive person and
children – GA)

19. • It is useful to
– Find threshold of hearing in young infants and
children within 5-10 dB
– To differentiate lesion of cochlear to that of CN VIII
th nerve
• Ratio between the amplitude of summating
potential to the AP is less than 30%
• Increase in ratio – indicative of Ménière’s
disease

20. AUDITORY BRAINSTEM RESPONSE
• Also known as BERA ( brainstem evoked response
audiometry)
• Elicit brainstem responses to auditory stimulation
by clicks or tone bursts
• Non invasive technique to find integrity of central
auditory pathways through the VIIIth nerve,
pons, and midbrain
• Measures the hearing sensitivity in the range of
1KHz – 4KHz

21. • Normal person- 7 waves are produced in the
first 10ms
• First, third and fifth waves are most stable and
are used in measurement
• The waves are studied for absolute latency,
interwave latency ( wave I and V) and the
amplitude

23. • Use for:
– Screening procedure for infants
– Determine threshold of hearing in infants
(uncooperative)
– Diagnose retrocochlear pathology particularly in
acoustic neuroma
– Diagnose brainstem pathology
– To monitor CN VIII intraoperatively in surgery of
acoustic neuromas to preserve the function of
cochlear nerve

24. AUDITORY STEADY STATE RESPONSE
(ASSR)
• Electrophysiological test which uses steady state pure tone
signals ( instead of transient signal of tone bursts in ABR)
• Steady state signals are modulated rapidly in amplitude and
frequency and thus give a frequency specific audiogram
• Detect hearing losses > 80 dB
• Detect hearing sensitivity in severe to profoundly deaf
infants
• Helps in selection of children for cochlear implantation at
an early age

25. OTOACOUSTIC EMISSIONS (OAE)
• Low intensity sounds produced by outer hair cells of a
normal cochlear
• Elicited by very sensitive microphone placed in external ear
canal and analysed by a computer
• Sound produced by outer ear travel in reverse direction:
outer hair cells-basilar membrane-perilymph- oval window-
ossicles- TM-ear canal
• help to detect fx of cochlear (OAEs produce only when
outer hair cells are healthy)
• Do not disappear in VIII th nerve pathology

26. Types of
OAEs
Evoked
OAEs
Transient
evoked OAEs
Distorted
Product OAEs
Spontaneous
OAEs
Present in healthy
normal persons
where hearing loss
do not exceed 30dB.
They are absent in
50% normal persons
A series of click
stimuli are
presented at
80-85 dB SPL
and response
are recorded
Two tones are
simultaneously
presented to the
cochlear to produce
distortion products.
Used to test hearing
in the range 1-8 KHz

27. • Uses:
– Screening test of hearing in neonates,
uncooperative, and mentally challenged person
after sedation
– Distinguish cochlear from retrocochlear hearing
loss, OAEs are absent in cochlear lesions. They
detect ototoxic effects earlier than pure tone
audiometry
– Useful to diagnosed retrocochlear pathology

28. CENTRAL AUDITORY TEST
• Patients with central auditory disorders have
difficulty to hear in noisy environments, or
when speech is distorted and not clearly
spoken
• 3 types of speech discrimination tests;
– Monotic test
– Dichotic test
– Binaural test

29. • Monotic test: test for lesions of brain and cortex
• Dichotic test; test for temporal lobe lesions
• Binaural tests: identify integration of information
from both ears
• Not routinely used

30. THANK YOU