diagnostic audiology, audiometry, tympanometry and OAE.pptx

Title: Diagnostic
Audiology: Unveiling the
Sounds of Diagnosis
DR ABDALLA ABDAZIZ

Introduction
• Diagnostic Audiology:
• Specialized branch of
audiology focused on
assessing and diagnosing
hearing and balance
disorders
• Scope:
• Identification of hearing
impairments
• Evaluation of auditory
processing
• Differential diagnosis of
various hearing-related

ASSESSMENT OF HEARING LOSS
HISTORY :
• Otalgia
• Ear discharge
• Hearing impairment – Onset, duration, progression,
unilateral/bilateral
• Tinnitus
• Vertigo
• Blocked sensation
• Feeling of fullness
• Neuro-otological symptoms – Fever, Headache, Facial
nerve palsy,

EXAMINATION
Pinna , Pre-auricular and Post-auricular regions
• External auditory canal
• Tympanic membrane
• Middle ear
• Mastoid
• Eustachian tube
• Facial nerve

CLINICAL TESTS OF HEARING
 FINGER FRICTION TEST : Rough method of screening.
Snapping the
fingers close to the patient’s ear
• WATCH TEST : Clicking watch brought close to the ear and
the distance at
which it is heard is measured. Obsolete now
• SPEECH / VOICE TESTS :
Normal person hears conversational voice -12ft, whisper -6ft
Test conducted in reasonably quite surroundings
Patient’s eyes are shielded
Test ear towards examiner at a distance of 6ft
Distance at which conversational and whispered voice are

Key Components of Diagnostic
Audiology
Subjective tests Objective tests
Tunning fork
Finger Friction Test
Watch Test
Speech / Voice Tests
Pure tone audiometry
Speech audiometry
Speech reception threshold
Speech discrimination score
Impedance audiometry
Otoacoustic Emissions
Brainstem Evoked Response
Electrocochleography
Auditory Steady State
Response
Auditory Brainstem Response

TUNING FORK TESTS
 RINNE’S TEST
 WEBER’S TEST
 ABSOLUTE BONE CONDUCTION TEST
 SCHWABACH’S TEST
 BING TEST
 GELLE’S TEST

TUNING FORK
Tuning fork was invented by John Shore in 1711.
These tests are qualitative tests as these indicate the type of
hearing loss.
Tuning forks emit pure tones and allow comparison of air
conduction with bone conduction.
Tests are done with various tuning forks, but 512 Hz is the most
commonly used as its rate of tone decay is not rapid and sound
is quite distinct from ambient noise.
Higher frequencies decay faster and with lower frequencies,
patient perceives the vibrations more than the sound.
The tuning fork should be held firmly by the stem and struck
lightly against resilient surface such as elbow, palm of the hand
or the ‘padded’ edge of a table.

TUNING FORK
Air conduction (AC) is tested by placing the
tuning fork 1/2 to 1 inch in front of and
parallel to the external acoustic meatus. It
indicates the integrity of tympano-ossicular
chain. Air conduction (AC) is better termed
as Ossicular conduction.
Bone conduction (BC) is tested by placing
the base of tuning fork on mastoid bone or
on the forehead.
a. BC signifies sound conduction through
cochlea, auditory nerve and its central
connections and hence provides
information about the integrity of inner ear.
b. Sound through BC is transmitted by

RINNE’S TEST
Air conduction of the ear is
compared with it’s bone conduction
A vibrating tuning fork is placed on
the patient’s mastoid and when he
tells it stoped hearing, it is brought
beside the meatus
If he still hears, AC > BC
Positive Rinnes’ (AC > BC) Normal
hearing, Sensorineural hearing loss
Negative Rinne’s (BC > AC)
Conductive hearing loss

RINNE’S TEST INTREPRETATION
• Prediction of air-bone gap with tuning
forks of frequency 256, 512 and 1024 Hz
• Rinne negative for 256, positive for 512
AB gap of 20-30 dB
• Rinne negative for 256 and 512, positive for
1024 AB gap of 30-45 dB
• Rinne negative for all three tuning forks,
256, 512 and 1024 Hz AB gap of 45-60 dB

WEBER’S TEST
Vibrating tuning fork placed on
the middle of the forehead or
vertex
Sound travels directly to the
cochlea via bone
Patient is asked in which ear is
the sound heard
Normal – Equal on both sides
Conductive deafness Lateralized
to worse ear
Sensorineural deafness
Lateralized to better ear

ABSOLUTE BONE CONDUCTION TEST
Patient’s bone conduction is
compared with that of the examiner
EAC of patient and examiner is
occluded – to prevent ambient noise
entering through air conduction
Conductive deafness – Bone
conduction is same as that of
examiner
Sensorineural deafness – Bone
conduction is reduced compared to
examiner

SCHWABACH’S TEST
Bone conduction of patient
compared to examiner
EAC is not occluded
Conductive deafness – Bone
conduction equal to that of
examiner
Sensorineural deafness –
Bone conduction reduced
compared to examiner

BING TEST
Test of bone conduction
Examines the effect of occlusion of ear
canal on hearing Vibrating tuning fork
placed on mastoid.
The examiner alternately closes and
opens the ear canal by pressing on the
tragus inwards
Bing Positive : When sound is louder
with the ear canal occluded. In normal
hearing and sensorineural hearing loss
Bing negative : No change in loudness
with the canal occluded. In conductive
hearing loss

GELLE’S TEST
Test of bone conduction Examines the
effect of increased air pressure in ear
canal on hearing Vibrating tuning fork is
placed on the mastoid.
Changes in air pressure in EAC brought
about by Siegel’s speculum
Gelle’s positive – Decreased hearing on
increased pressure. In normal
individuals and sensorineural hearing
loss.
Gelle’s negative – No change in hearing
on increased pressure. Seen in ossicular
chain fixation (Otosclerosis) or

Audiometric Testing
• Pure-Tone Audiometry:
• Purpose: Measures hearing thresholds across
different frequencies (Hz).
• Procedure: Patients respond to pure tones at varying
intensities, identifying the softest sound they can
hear.
• Results: Audiogram mapping hearing sensitivity,
aiding in the identification and classification of
hearing loss.
• Speech Audiometry:
• Purpose: Assesses speech understanding and
discrimination.
• Procedure: Measures the ability to recognize and
repeat spoken words at different intensities.
• Results: Provides insights into speech intelligibility
and helps determine hearing aid candidacy.

PURE TONE AUDIOMETRY
Hearing sensitivity of a subject for
pure tone sounds
Pure tone : Sound sensation produced
by the sinusoidal wave pattern when an
object vibrates in a fixed single
frequency
Complex sound: Sound of various
frequencies and intensities – mixture of
different pure tone sounds
Audiometer: An electronic device that
consists of an audio-oscillator which
generates pure tone sounds of various
frequencies.

AIMS OF PURE TONE AUDIOMETRY
If the subject has any definite
auditory disorder
If the hearing loss is conductive
/ sensorineural / mixed
If sensorineural, whether it is
cochlear or retrocochlear
Degree of hearing dysfunction

Advantages Of Pure Tone
Audiometry
Pure tone audiometry is a reliable
method of testing the hearing acuity
and gives information about the
quantity and quality of hearing loss
In some cases, pattern of curve points
towards a disease such as
otospongiosis, acoustic trauma,
Meniere's disease and presbycusis.
Test record is good for future
reference.
To know the degree of hearing
handicap and for prescribing a hearing
aid.

Pure-Tone Air-Conduction Testing
Pure-tone air-conduction thresholds
measure the function of the total
hearing system, including the
external, middle, and inner ear.
In typical audiometric testing, pure
tones that range in octave spacings
from 250 to 8000 Hz are presented
to the listener by headphones or
insert earphones.
Threshold is usually determined by
the use of a version of the Hughson-
Westlake “ascending method,” in
which sounds are initially presented
well above threshold, and are then
presented in decreasing steps of 10
to 15 dB until the sound is inaudible.

Cont.
When plotted on an
audiogram, pure-tone
thresholds also provide
information regarding the
severity of the hearing
loss.
Thresholds that fall into
the 0- to 25-dB range are
considered normal,
whereas thresholds
greater than 25 dB
represent various levels
of hearing loss (see Fig.

Pure-Tone Bone-Conduction Testing
Pure-tone bone-conduction
thresholds provide auditory
threshold information when the
cochlea is stimulated more or less
directly, with stimuli bypassing
external and middle ear structures.
Differences between thresholds
obtained through air and bone
conduction are used to determine
the type of hearing loss (normal
hearing versus conductive loss
versus sensorineural hearing loss
[SNHL]) and the magnitude of
conductive hearing loss if it exists.

Technique
In bone conduction testing, a
bone oscillator is typically
placed on the mastoid
process. Although this
placement does not guarantee
that the responses obtained
are from the ear located on
the side on which the
oscillator was placed, such
placement provides an
enhanced dynamic range
compared with other
placements, such as at the

MASKING
• In pure tone audiometry, the
exact hearing threshold by air
and bone conduction for
different frequencies in each
ear should be calculated
separately and individually
• When sound is presented to
one ear, a part of it travels to
the other ear and stimulates
it too
• To overcome the problem of
cross-hearing, the non-test /

WHEN TO MASK
Cross hearing should be
suspected when air conduction
values in the test ear are above
40 – 45 dB (as the lower limit of
interaural attenuation is around
40 – 45 dB)
During air conduction –
contralateral ear should always
be masked if tones of 45 dB and
more are used During bone
conduction, both cochlea are
stimulated equally.
Hence, the non-test ear should
always be masked during bone

Relationship between
AC and BC
• The relationship between air-conduction
and bone-conduction thresholds is used
to determine the type of hearing loss.
• When air conduction thresholds are
elevated relative to normal bone-
conduction thresholds—a phenomenon
referred to as an air-bone gap —the loss is
classified as conductive (Fig. 133-2).
• When air-conduction and bone
conduction thresholds indicate the same
amount of hearing loss, the loss is
classified as sensorineural (Fig. 133-3).
• Finally, when air-conduction thresholds
are elevated relative to abnormal bone-

AMOUNT OF MASKING SOUND
REQUIRED
• The non-test ear is masked by
presenting a ‘noise’ that is loud
enough to prevent the tone from test
ear stimulating the non-test ear, but
not so loud that it will mask the
sensitivity of the test ear.
• • Intensity of the masking sound
Should neither under mask nor over
mask.

SOUNDS USED FOR MASKING
WHITE NOISE : Broadband or wideband noise. Equal
amount of sound of all frequencies.
• NARROW BAND NOISE : More effective. Narrow
band of noise centered on the test tone frequency
with 100 to 200 Hz above and below that
frequency.
The masking noise varies for each frequency. The
band width which will provide the maximum
effective masking for a tone of a particular
frequency at minimum intensity is called critical
band width for that particular frequency.

INTERPRETATION OF AUDIOGRAMS
• WHO classification on the basis of pure
tone average of the thresholds for
frequencies 500, 1000, 2000 Hz
• • DEGREE OF HEARING LOSS :
• 0 to 25 dB : Normal for all practical
purposes
• 26 to 40 dB : Mild deafness
• 41 to 55 dB : Moderate deafness
• 56 to 70 dB : Moderately severe
deafness
• 71 to 90 dB : Severe deafness
• Above 90 dB: Profound deafness

LIMITATIONS OF PURE TONE
AUDIOMETRY
Subjective test
Patient should understand the
instructions – cannot be done in
children and psychiatric patients
Not accurate for medico-legal
purposes if malingering is
suspected
Does not evaluate the properties
of supra threshold hearing, like
frequency discrimination and
temporal resolution of sound
Does not identify the exact
nature of the pathology

Normal hearing
SNHL
CH
L
MIXED
HL

IMPEDANCE AUDIOMETRY
• The test measures the
impedance of middle ear
system at the level of
tympanic membrane due to
changes in air pressure in
external auditory meatus.
• • It consists of:
• 1. Tympanometry
• 2. Acoustic reflex
audiometry.

Advantages of Impedance Audiometry
1. Objective test
2. Differential diagnosis of conductive
and SNHL.
2. To find out the differential diagnosis
of conductive hearing Loss.
3. To know the site of lesion in facial
nerve palsy.
4. To test hearing acuity in infants and
children.
5. To find out malingers.
6. To find out lesions of brainstem

TYMPANOMETRY
• Tympanometry is an objective
audiometry and measures the
impedance (means resistance) offered
by the middle ear conducting apparatus
such as tympanic membrane (TM) and
ossicular chain and also the compliance
(suppleness) to sound pressure
transmission.
• It consists of the following:
• A probe fitted into external auditory
meatus connected to an oscillator,
which gives sound at 220 Hz
• An air pressure pump, which is used to

Cont.
• Principle : Sound strikes tympanic
membrane some energy is absorbed,
rest is reflected.
• Stiffer tympanic membrane reflects
more sound than a compliant one.
• By changing the pressure in a sealed
external auditory canal and
measuring the reflected sound
energy, it is possible to find the
compliance / stiffness of the
tympano-ossicular system healthy
or diseased status of the middle ear.

PATHOLOGIES WITH INCREASED
COMPLIANCE
PATHOLOGIES WITH DECREASED
COMPLIANCE
Ossicular discontinuity
 perforation of the tympanic
membrane (tympanosclerosis)
 Post stapedectomy ear
1. Otosclerosis
2. Adhesive or secretory otitis
media
3. Tumors in the middle ear –
glomus jugular
4. Ossicular fixations – fixed
malleus syndrome
5. Thickening of the tympanic
membrane

TYPES OF TYMPANOGRAMS
TYPE A : Peak is near 0 pressure.
TYPE As : Peak is at 0 but amplitude
of the peak is low. Due to
increased stiffness of the system
TYPE Ad : Peak is around 0 but
amplitude is abnormally high.
System is more compliant than
normal
TYPE B : Flat or dome shaped curve
denoting that pressure changes do
not have much effect on the
compliance.
TYPE C : Peak is shifted to the

diagnostic audiology, audiometry, tympanometry and OAE.pptx

SIGNIFICANCE OF TYMPANOGRAMS
TYPE A : Normal
tympanogram.
TYPE As : Otosclerosis,
tympanosclerosis, thick graft
in myringoplasty.
TYPE Ad : Ossicular
discontinuity, flaccid
tympanic membrane.
TYPE B : Impacted wax,
foreign body, secretory otitis
media, adhesive otitis media,
perforated TM.

ACOUSTIC / STAPEDIAL REFLEX TESTS
• Objective test, non-invasive, simple to
perform and requires very little time
(few minutes)
• • Helps in the following :
• 1. Elimination of middle ear pathology
• 2. Differentiation of cochlear from
retrocochlear pathology
• 3. Objective estimation of average
hearing threshold level
• 4. Detection of non-organic hearing loss
• 5. Identifying the level of lesion in
facial nerve paralysis

Cont.
• PRINCIPLE:
• • When a loud sound reaches the ear (70
-100 dB above the hearing threshold), the
intra-aural muscles, STAPEDIUS and
TENSOR TYMPANI contract reflexly.
• • The net result of the contraction of the
muscles leads to stiffening of the middle
ear conductive apparatus and changing
the impedance of the middle ear system
• • Stapedius is innervated by branch of
facial nerve. Tensor tympani by
mandibular branch of trigeminal nerve.
• • For all practical purposes, changes in
impedance of the middle ear are caused

ABSENCE OF ACOUSTIC REFLEX
Disorders on the afferent
side :
Disorders on the efferent
side :
• Disease in the ipsilateral
middle ear
• Lesion in the ipsilateral
cochlea or 8th cranial nerve.
• Lesion in the cochlear
nucleus or superior olivary
complex.
• Lesion in the facial nerve
nucleus in brainstem.
• Facial nerve palsy at a level
proximal to the nerve to
stapedius –
Ramsay Hunt syndrome.
• Disease of stapedius muscle
– myasthenia gravis.
• Lesion in the middle ear –
otosclerosis, ossicular
discontinuity,

EUSTACHIAN TUBE FUNCTION TEST
• Physiological functions of the
eustachian tube :
1.Maintenance of equality of air
pressure between the middle ear
and the ambient atmosphere –
VENTILATORY FUNCTION (major)
2.Drainage of the mucous from the
ear to the nasopharynx –
MUCOCILIARY CLEARANCE
FUNCTION
• Muscles causing intermittent
opening of the eustachian tube –

EUSTACHIAN TUBE FUNCTION
TEST(cont.)
• Modern impedance audiometers can test Eustachian
tube function by 2 methods :
• 1. WILLIAM’S TEST : Test of tubal function in
subjects with an intact tympanic membrane
• 2. TOYNBEE’S TEST : Test of tubal function in
subjects with perforated tympanic membrane.

WILLIAM’S TEST
 Measures middle ear pressure
in 3 conditions – At the start of
the test (resting pressure),
after the patient swallows
(with nose and mouth closed),
after performing Valsalva
 Normally, the ambient middle
ear pressure should be at or
near atmospheric pressure,
should become negative on
swallowing and positive on

TOYNBEE’S TEST
• Done in patients with perforated
tympanic membrane
• The audiometer is programmed to
artificially increase or decrease the air
pressure in the middle ear each time the
patient swallows.
• Advantage : Can be done on a pressure
differential – positive pressure at the
tympanic end of the tube and ambient
pressure at the nasopharyngeal end of the
tube.
• Air pressure at the middle ear end of the
Eustachian tube is first changed to either

BRAINSTEM EVOKED RESPONSE
AUDIOMETRY
Introduced by Jewitt in 1970
• Non-invasive objective audiological investigation
• PRINCIPLE : Sound waves entering cochlea are transduced
to electric potentials and transmitted via VIII nerve through
brainstem and then to the auditory cortex
• Passage of the impulse through the auditory pathway
generates an electrical activity
• These electrical responses are picked up by surface
electrodes and represented graphically
• Each wave in the graph is generated by major processing
centers of the auditory system.

WAVES IN BERA
WAVE SITE OF NEURAL GENERATOR
WAVE I
WAVE II
WAVE III
WAVE IV
WAVE V
WAVE VI & VII
Cochlear nerve (distal end)
Cochlear nerve (proximal
end)
Cochlear nucleus
Superior olivary complex
Lateral lemniscus
Inferior colliculus

CLINICAL USES OF BERA
1. Estimation of hearing threshold
2. Diagnosis of lesions of VII cranial nerve
3. Identification of nature of deafness
4. Screening procedure for infants
5. To diagnose brainstem pathology. Ex:
multiple sclerosis or pontine tumours
6. To monitor VIII cranial nerve
intraoperatively in surgery of acoustic
neuromas to preserve the function of
VIII nerve

Otoacoustic Emissions (OAEs)
• Basics of OAEs:
• Purpose: Measures the sound emitted
by the inner ear in response to an
acoustic stimulus.
• Procedure: A small probe is placed in
the ear canal, and responses are
recorded.
• Results: Presence or absence of OAEs
aids in identifying cochlear damage or
dysfunction.

OTOACOUSTIC EMISSIONS
• They are low intensity
sounds produced by outer
hair cells of a normal cochlea
due to their biological
activity.
• • Can be picked up, recorded
and measured by placing a
microphone – receiver in the
deep external meatus.
• • Direction of travel of OAE :
Outer hair cells basilar
membrane Perilymph Oval

Cont.
Types of OAE
• 1. Spontaneous OAEs—arise from
outer hair cells, inhibited by
ototoxic drugs.
• 2. Stimulus frequency OAEs—
technically difficult to record.
• 3. Transient evoked OAEs—elicited
in response to transient clicks.
• 4. Distortion product OAEs—in
response to simultaneous tones.

OTOACOUSTIC EMISSIONS
Uses of OAE:
• 1. These are very useful in ‘screening of
neonates and high risk infants’ for
hearing loss.
• 2. Diagnosing central processing
auditory disorders, particularly auditory
neuropathy.
• 3. Differentiate cochlear from
retrocochlear pathology.
• 4. Detect early changes in ototoxicity
and noise induced hearing loss.
• 5. To monitor Ménière’s disease.
• 6. Malingerers.

ASSESSING THE DEAF CHILD
Objectives :
• To ascertain whether the child has
any deafness or not.
• If deafness is present, whether
unilateral or bilateral.
• To document the degree of
functional impairment for each ear.
• To establish a topographical
localization of the lesion.
• To establish an etiological diagnosis
• To establish management protocols

ASSESSMENT OF HEARING IN INFANTS
AND CHILDREN
BEHAVIOUR TESTS :
• Auditory signals presented to an
infant produces a change in behavior –
Alerting, cessation of activity,
widening of eyes or facial grimacing.
• MORO’S reflex : Sudden movement
of limbs and extension of head in
response to sound of 80 – 90 dB
• COCHLEOPALPEBRAL reflex : Child
responds by a blink to a loud sound
• CESSATION reflex : Child stops
activity or starts crying in response to

Auditory Brainstem Response (ABR)
• Purpose: Evaluates the electrical activity in the auditory
nerve and brainstem.
• Procedure: Electrodes are placed on the scalp to record
responses to auditory stimuli.
• Results: Useful in diagnosing retro cochlear pathology and
assessing neural integrity, especially in difficult-to-test
populations.

THANK YOU
WEBALE
MAHADSANID
GRACIAS
MERCI

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