A brief introduction to understand the topics

1. FUNCTIONAL ASSESSMENT OF
HEARING & VESTIBULAR
FUNCTION TESTS
Dr Harjitpal Singh
Assistant Professor(ENT),
Dr RKGMC, Hamirpur

2. INTRODUCTION
• HEARING LOSS : Impairment of hearing
• Characterised by :
Type – Conductive, Sensorineural, Mixed
Location of cause – External ear, Middle ear, cochlea, auditory nerve,
central cause
Onset – Insidious or Sudden
Rate of progression
Degree of loss – Mild, moderate, moderately severe, severe, profound
Unilateral or Bilateral

3. CLASSIFICATION OF HEARING LOSS
HEARING LOSS
ACQUIRED
ORGANIC FUNCTIONAL
CONGENITAL
CONDUCTIVE SENSORINEURAL MIXED

4. CLASSIFICATION OF HEARING LOSS(cont.)
ACQUIRED
ORGANIC
CONDUCTIVE SENSORINEURAL MIXED
FUNCTIONAL
PSYCHOSOMATIC
MALINGERING
HYSTERICAL

5. CLASSIFICATION OF HEARING LOSS(cont.)
SENSORINEURAL
SENSORY NEURAL
PERIPHERAL CENTRAL

6. CONGENITAL HEARING IMPAIRMENT
CONDUCTIVE
• Exostosis
• Microtia
• Absence of pinna
• Congenital cholesteatoma
• EAC atresia with/without
ossicular fixation : Treacher
Collins, Klippel Fiel, Alport’s,
Goldenhar, Mohr’s
• Associated eye disorders:
Cryptophtalmus, Duane’s
• Associated renal disorders:
Nephrosis, Taylor’s syn.
SENSORINEURAL
• Michael’s aplasia
• Mondini dysplasia
• Scheibe dysplasia
• Bing – Siebenmann dysplasia
• Alexander dysplasia
• Enlarged vestibular aqueduct
• Semicircular canal malformations

7. CONGENITAL SENSORINEURAL HEARING
IMPAIRMENT
• MICHEL APLASIA : Complete lack of development of inner ear
• MONDINI DYSPLASIA : Incomplete development of bony and
membranous labyrinth
• SCHEIBE DYSPLASIA : Cochleosaccular aplasia with normal bony labyrinth
• BING – SIEBENMANN DYSPLASIA : Malformation of membranous
labyrinth with a normal osseous labyrinth
• ALEXANDER DYSPLASIA : Affects only the basal turn of membranous
cochlea. High frequencies are affected

8. ACQUIRED CAUSES OF CONDUCTIVE HEARING
LOSS
• EXTERNAL EAR :
Obstruction of EAC  Wax, foreign body, furuncle, benign or malignant tumour,
atresia of canal
• MIDDLE EAR :
Perforation of tympanic membrane – Traumatic or infective
Fluid in middle ear – Acute otitis media, serous otitis media, hemotympanum
Disruption of ossicles – Trauma, CSOM, cholesteatoma
Fixation of ossicles – Otosclerosis
Eustachian tube blockage – serous otitis media, retracted tympanic membrane

9. ACQUIRED CAUSES OF SENSORINEURAL HEARING LOSS
• Infections of labyrinth – Viral, bacterial, spirochaetal
• Trauma to labyrinth or VIII nerve – Fracture of temporal bone
• Noise induced hearing loss
• Ototoxic drugs
• Presbycusis
• Meniere’s disease
• Acoustic neuroma
• Sudden hearing loss
• Familial progressive sensorineural hearing loss
• Systemic disorders – Diabetes, Hypothyroidism, autoimmune disorders,
multiple sclerosis etc.

10. 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,
Vomiting, diplopia

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

12. 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 -12m, whisper -6m
Test conducted in reasonably quite surroundings
Patient’s eyes are shielded
Test ear towards examiner at a distance of 6m
Distance at which conversational and whispered voice are heard is
measured

13. TUNING FORK TESTS
• RINNE’S TEST
• WEBER’S TEST
• ABSOLUTE BONE CONDUCTION TEST
• SCHWABACH’S TEST
• BING TEST
• GELLE’S TEST

14. TUNING FORK TESTS(cont.)
• 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, heel of the hand or the ‘padded’
edge of a table.

15. TUNING FORK TESTS(cont.)
• 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.
• BC signifies sound conduction through cochlea, auditory nerve and its central
connections and hence provides information about the integrity of inner ear.
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 vibration of skull bones or through
one is own voice.
• Two different types of vibration occur, i.e.
a. Inertial type (below 800) when skull vibrates as one unit and lagging
behind of ossicles, mandible and cochlear fluid occurs due to inertia.
b. Compression type (for frequency above 800) in this the vibrations act
on the fluids of inner ear and cause its movements.

17. 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
stops 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

18. RINNE’S TEST(cont.)
• 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

19. RINNE’S TEST(cont.)
• Seen in severe unilateral sensorineural hearing loss
• Does not perceive sound by air conduction, responds to bone
conduction
• Bone conduction response  from opposite ear due to transcranial
transmission of sound
• Correct diagnosis  by masking the non-test ear with Barany’s noise
box

20. 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
Lateralised to worse ear
• Sensorineural deafness
Lateralised to better ear

21. 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

22. 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

23. 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

24. 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 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 disruption

25. AUDIOMETRIC TESTS
SUBJECTIVE
• Pure tone audiometry
• Speech audiometry
• Speech reception threshold
• Speech discrimination score
• Bekesy audiometry
OBJECTIVE
• Impedance audiometry
• Otoacoustic Emissions
• Brainstem Evoked Response
Audiometry
• Electrocochleography
• Auditory Steady State Response

26. 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

27. 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

28. 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,
Ménière’s disease and presbycusis.
•Test record is good for future reference.
•To know the degree of hearing handicap and for
prescribing a hearing aid.
•Also helps to find out speech reception threshold.
•Medicolegal purposes.

29. 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 /
better ear should be masked

30. 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
conduction

31. 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
undermask nor overmask

32. 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
• COMPLEX NOISE : Made up of a low frequency fundamental plus the
multiples of that frequency up to 4000 Hz

33. 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

34. 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

37. AUDIOGRAM

38. NORMAL AUDIOGRAM

39. SENSORINEURAL HEARING LOSS

40. CONDUCTIVE HEARING LOSS

41. MIXED HEARING LOSS

42. BEHAVIORAL TESTS
• The portion of the auditory system from the auricle to the
cochlea – Peripheral auditory system
• The peripheral part can be assessed by different behavioural
tests namely :
1.Threshold Tone Decay Test
2.Short Increment Sensitivity Index
3.Alternate Binaural Loudness Balance test
These tests are subjective tests

43. TONE DECAY TEST
•Helps in the detection of site of pathology in the
sensorineural pathway
•Pathology in the auditory nerve causes an abnormally
rapid deterioration in the threshold of hearing of a tone
if that tone is presented continuously (as a sustained
signal) to the ear
•In TDT, the rapidity of this deterioration is measured
•Principle : Wedensky’s peripheral nerve inhibition

44. TONE DECAY TEST(cont.)
Various methods of measuring tone decay :
1.CARHART’S METHOD : Most popular
2.GREEN’S MODIFIED METHOD
3.OLSEN AND NOFFSINGER METHOD
4.ROSENBERG’S METHOD
5.SUPRATHRESHOLD ADAPTATION TEST

45. INTERPRETATION OF TONE DECAY
• Normal – if decay is 0 – 5 dB
• Mild – if decay is 10 – 15 dB
• Moderate – if decay is 20 -25 dB
• Severe – if decay is 30 dB and above
Tone decay in excess of 30 dB should arouse a
suspicion of a retro cochlear lesion and the patient should be
subjected to a detailed neuro-otological examination including :
acoustic reflex decay, brainstem evoked response audiometry,
CT and MRI.

46. RECRUITMENT
• Coined by Fowler in 1937
• Defined as abnormally steep growth of loudness with increasing
intensity and is usually associated with a sensorineural deafness
due to a cochlear pathology
• Recruitment is a normal phenomenon in high intensities of sound.
Recruitment is present in all ears when sounds of high intensity
are used – normal ear or with cochlear pathology
• Recruitment is not present in a case of retrocochlear pathology –
accounted for by the defective transmission in a diseased auditory
nerve
• Presence or absence of recruitment can be directly tested by –
ALTERNATE BINAURAL LOUDNESS BALANCE test – Described by
Fowler
• Indirect test for recruitment – SHORT INCREMENT SENSITIVITY
INDEX – First described by Jerger, Sheld and Harford in 1959

47. SHORT INCREMENT SENSITIVITY INDEX
• Determines the capacity of the patient to detect a brief 1 dB increment
in a 20 dB suprathreshold tone (carrier tone) in various frequencies
• Usually tested at 1000 and 4000 Hz, but any frequency above 250 Hz
may be used
• At intervals of 5 seconds a brief increase in the intensity of the carrier
tone occurs
• This increase in intensity may be varied from 6 dB to 1 dB
• The increase takes 50 ms, remains at the specified level for 200 ms and
returns to original carrier tone in 50 ms
• Twenty such 1 dB increments are presented to the ear and the patient is
asked to count the number of increments he could correctly identify
• This multiplied by 5 gives the percentage SISI score
• The patient is initially familiarised with increments of 6dB, 5 dB etc.
before starting the test with 1 dB increment

48. INTERPRETATION OF SISI TEST
•Scores between 70% to 100% - Positive SISI –
Indicates a cochlear lesion
•Scores between 0% to 20% - Negative SISI –
Suggests a retrocochlear pathology. But may also be
seen in ears with normal hearing or with conductive
deafness

49. ALTERNATE BINAURAL LOUDNESS BALANCE TEST
• Requires specially designed audiometers which can
alternately send two tones of the same frequency in the two
ears
• The tone stays for a duration of ½ to 1 second in each ear,
but the duration must be equal in the two ears
• Intensity is controlled by 2 separate attenuators for each ear
• The patient is instructed to indicate in which ear the sound
appears to be louder and ultimately say when the sound in
the two ears appear to be of equal loudness
• Results are plotted as a graph – poorer ear data on the
abscissa and better ear data on the ordinate

50. INTERPRETATION OF ABLB
One of the following four possibilities :
1. Absence of recruitment : Equal loudness at equal sensation levels
2. Complete recruitment : Equal loudness at equal intensities or
equal hearing levels
3. Partial recruitment : Difference in the hearing level between the
two ears for equal loudness gradually diminishes with increasing
intensities but the difference never becomes zero
4. Decruitment or Loudness reversal : When the growth in loudness
in the poorer ear is slower than in the better ear – there is
decruitment

51. LIMITATION OF ABLB
•Can be carried out when there is a substantial
difference in hearing level between the two ears
•Suitable for cases of unilateral deafness
•To overcome this, Monoaural Loudness Balance test
(MLB) was devised
•Can be done in bilateral symmetrical deafness
•Measures the growth in loudness between two
frequencies in the same ear

52. 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. 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.

53. 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 alter the pressure in the meatus
 A microphone
• 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

54. PATHOLOGIES WITH INCREASED COMPLIANCE
•Ossicular discontinuity
•Scarring of the tympanic membrane
•Post stapedectomy ear
•Very large tympanic membrane – very rare

55. PATHOLOGIES WITH DECREASED COMPLIANCE
•Otosclerosis
•Adhesive or secretory otitis media
•Tumours in the middle ear – glomus jugulare
•Ossicular fixations – fixed malleus syndrome
•Thickening of the tympanic membrane

56. PATHOLOGIES WITH NORMAL COMPLIANCE
•Eustachian tube obstruction only, without secretory
changes in the middle ear
•Some cases of otosclerosis

57. 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 incresed 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 negative side

58. 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
•TYPE C : Retracted tympanic membrane

61. 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
6. Hearing acuity in infants and children.

62. ACOUSTIC / STAPEDIAL REFLEX TESTS(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 by contraction of stapedius muscle
only

63. ABSENCE OF ACOUSTIC REFLEX
Disorders on the afferent 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
Disorders on the efferent side :
• 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,
atelectasis

64. 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 –
Tensor palatini and levator veli palatini – contract during
swallowing

65. 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

66. EUSTACHIAN TUBE FUNCTION TEST(cont.)
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 performing Valsalva
• Any deviation from this - Abnormal

67. EUSTACHIAN TUBE FUNCTION TEST(cont.)
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 +250 or -250 mmof water. Patient is
asked to swallow repeatedly. Normally, the positive or
negative pressure should be totally neutralised in 3-5
swallows. If not – impaired tubal function

68. 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

69. BERA
• Pure tone audiogram should preferably be done prior to
BERA because, the sound stimulus has to be presented at a
fixed suprathreshold level (usually 60 dB above threshold)
and also the interpretation of BERA is dependent on
audiometric contour
• Sound stimulus : Broad band click of 100 microseconds
duration
• Broadband click stimulated synchronously a large number of
neurons and elicits a BERA tracing which is clear, sharp and
well marked with distinctly recognisable peaks in the graph

71. PLACEMENT OF ELECTRODES

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

73. NORMAL BERA WAVEFORM

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

75. 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 window  Ossicles 
Tympanic membrane  Ear canal

76. OTOACOUSTIC EMISSIONS(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.

77. OTOACOUSTIC EMISSIONS(cont.)
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.
7. Provides objective confirmation of cochlear dysfunction in
tinnitus.

78. VESTIBULAR FUNCTION TESTS
• Derangement of vestibular system is indicated by
Vertigo and
Nystagmus, which is defined as involuntary, rhythmical,
oscillatory movements of eyes away from the
direction of gaze.
• Nystagmus of vestibular origin has 2 components:
• Slow component and quick (fast/corrective)
component and by convention, nystagmus is
named after quick component – Right or Left
• Quick component of nystagmus is eliminated when
the patient is put under anesthesia.

79. VESTIBULAR FUNCTION TESTS(cont.)
Degrees of Nystagmus
• First degree is a weak nystagmus and it is present whenthe patient
looks in the direction of quick component
• Second degree nystagmus appears when the patient is looking
straight ahead.
• Third degree nystagmus (severe) appears when the patient is looking
towards slow component.

80. VESTIBULAR FUNCTION TESTS(cont.)
Types of Nystagmus
• Central It is coarse, irregular and does not fatigue. It can be in any
direction. Vertigo is usually not present. Symptoms and signs of
intracranial disease are present.
• Ocular It is of congenital type and is pendular. Paralysis of external
rectus may simulate nystagmus.
• Vestibular It is rhythmic, has a slow and fast component, fatigues
easily, vertigo is present, duration is of less than 1 minute and
latency is 2 to 20 second. It can be spontaneous, positional or
induced.
• Spontaneous nystagmus It is horizontal, rotatory or mixed type and
does not last for more than 3 weeks and vertigo is also present.

81. VESTIBULAR FUNCTION TESTS(cont.)
Types of Nystagmus
• Positional nystagmus
• It appears and reappears when the head is put in the same
position.
• Vertigo is not much and it may be because of vestibular or
central causes
• A nystagmus, which is fatigable and short lasting is usually of
peripheral origin and the one not fatigable and with
changing direction is of central type.
• Induced nystagmus This type of nystagmus can be induced by
rotation in a chair, thermal stimuli (caloric test) or by visual
stimulation such as looking at a series of objects moving from
one side to other.

82. 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 localisation of the lesion
• To establish an etiological diagnosis
• To establish management protocols

83. ASSESSING THE DEAF CHILD(cont.)
• A detailed history is essential – Prenatal, perinatal or
postnatal causes, family history
• A detailed physical and otologic examination and
investigations depending on the cause suspected
• Suspicion of hearing loss when
a.Child sleeps through loud noises unperturbed
b.Fails to startle to loud sounds
c.Fails to develop speech at 1 – 2 years

84. ASSESSMENT OF HEARING IN INFANTS AND CHILDREN
BEHAVIOUR TESTS :
• Auditory signals presented to an infant produces a change in
behaviour – 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 a loud sound

85. ASSESSMENT OF HEARING IN INFANTS AND
CHILDREN(cont.)
DISTRACTION TECHNIQUES :
Used in children 6 – 7 months old.
Child turns his head to locate the source of sound
CONDITIONING TECHNIQUES :
1. Visual reinforcement audiometry
2. Play audiometry
3. Speech audiometry

86. ASSESSMENT OF HEARING IN INFANTS
AND CHILDREN(cont.)
OBJECTIVE TESTS :
• EVOKED RESPONSE AUDIOMETRY :
1.Electrocochleography
2.Brainstem Evoked Response Audiometry
• OTOACOUSTIC EMISSIONS
• IMPEDANCE AUDIOMETRY

87. THANK YOU