A review for Hearing loss causes and Hearing aids ototoxicity has been left out other then a mention as it is separate topic. PPt prepared for in ward discussion with colleagues.

1. Hearing loss & Hearing Aids
Dr.R.Malarvizhi
DLO 2nd yr
MMC

3. Hearing loss
• Congenital or acquired
• Conductive, sensorineural or mixed
• External, middle or inner

4. External ear- conductive
• Foreign body
• Wax, keratosis obliterans
• Otitis externa
• Exostosis
• Trauma
• Tumors – benign & malignant
• Myringitis
• External auditory canal atresia unilatral or bilateral
• EAC hypoplasia – membranous / bony
• Rudimentary TM, perforation –traumatic or com
• Microtia

5. • Altmann – 3 grades
• Congenital
▫ Nager s/d
▫ Hemifacial microsomia
▫ Goldenhar s/d
▫ Crouzen s/d
▫ Apert’s s/d
▫ Downs s/d
▫ Pierre robin s/d
▫ Treacher collins s/d

6. Middle ear- conductive
• Congenital
▫ Ossicular
▫ Nager s/d, downs s/d, pierre robins, achondroplasia, osteogenesis
imperfecta, treacher collins
▫ Absence of OW, RW or persistance of stapedial artery
• Infections-aom, com, cholesteatoma,ANOM .
• Adhesive OM , TS, aural polyp
• Otosclerosis
• OME
• Allergy
• Barotrauma
• Hemotympanum
• Iatrogenic
• ME growth- glomus , SqCC
• Altmann grading

7. Eustachian
• Tubal catarrh / obstruction
• ET dysfunction
• Barotrauma
• Enlarged adenoids
• Nasopharyngeal growths- benign & malignant

8. Inner ear-sensorineural
• Cochlear & retro-cochlear
• Special entites
▫ NIHL
▫ Ototoxicity
▫ Age related sensori neural hearing loss
▫ Idiopathic sudden onset sensorineural hearing
loss

9. Cochlear
• Inflammatory – bacterial, viral, chlamydial
• Traumatic
• Vascular
• Haematological
• Connective tissue disorders
• Endolymphatic hydrops
• Metabolic
• Drugs
• Ototoxicity
• Skeletal system

10. Retrocochlear
• Meningitis
• Multiple sclerosis
• Frireich ataxia
• Lateral sclerosis
• VKH s/d
• Xeroderma pigmentosa
• Tumors- vestibular schwannoma, meningioma,
cholesteatoma, haemangioma in CP angle
• Central deafness

11. • Drugs n noise on Outer hair cells- basal turn-
high frequncy
• Vestibular – type I more sensitive
• Cochlear – outer haircells more susceptible
• Crista ampulli are more sensitive than maculi
• Loss of cochlear hair cells results in sec
degeneration of auditory nerve
• Cisplatin- HF
• Mitochondrial susceptibilty to aminoglycoside
• Cisplatin- individual susceptibilty

12. supplements
Ototoxic insult
Antioxidant systems Reactive oxygen species
Cellular redox status
Activation of transcription factors
Specific gene transcription
Homeostatic survival pathways
Cell death pathways, apoptosis,
necrosis

13. Age related SNHL
• External ear
▫ Increased cerumen
production
▫ Reduced epithelial migration
▫ Increased hair growth
▫ Potential collapse of ear canal
▫ Enlargement of pinna
• Middle ear
▫ Stiffening, thinning, loss of
vascularity of TM
▫ Arthritic changes and
ossification in ossicles and
ossicular joints
▫ Degeneration of middle ear
muscles
▫ Calcification of cartilaginous
support of ET

14. Schuknecht 6 distinct types
• I Sensory type- loss of hair cells and
sustentacular cells at the basal end of organ of
corti
• II Neural type- degenration of neurons of
cochlear nerve with resulting cochlear ganglion
cell loss
• III Vascular / Metabolic- atrophy of cochlear
stria vascularis with associated loss of strial
tissue primarily in the apical and middle turns of
cochlea

15. • IV type mechanical/ cochlear conductive- stiffness
of cochlear basal membrane, asso with increase in
number of fibrillar layers of basilar membrane
• V type intermediate, change in charac of cochlear
duct not evident in light microscopy but alter
function at submicroscopic level. Changes in
intracellular organelles involved in cell metabolism
decrease in synapse numbers and changes in
endolymph composition
• VI type mixed

16. • Neural type – MC
• HF loss
• Gene ‘ahl’ , autosomal recessive
• Rate of deterioration increase with age
• Onset variable, once certain amt HL occurs (75-
80dB) progression very slow, particularly HF
• PTA
• MRI
• Binaural Hearing aids

17. Noise Induced Hearing Loss
• NIHL refers to reduction in auditory
acuityassociated with noise exposure
• NI temporary threshold shift- exposed to noise
at damaging intensities for sufficient period of
time , a temporary depression of hearing results,
disappearing after min or hrs of rest.
PHYSIOLOGICAL phenomenon. Steep isolated
dip 3,4or 6 kHz. A low intensity sound before
subsequent high intensity sound reduces the
temporary threshold shift

18. • NI permanent threshold shift ( occupational HL,
industrial HL, Boiler’s disease)
Occurs when exposure to noise is longer or in
greater intensity or both, a stage is reached when
d HL no longer returns to normal. Rate of loss HF
in early stages and low F in late stages.
• Under water (immersion blast) intensity of
sound pressure wave is 4x than in air . So
damage more in water.

19. • Gene ahl predisposition
• Acoustic overstimulation – excessive release of
neurotransmitters
• Stimulation with sound of high intensity
decreases cochlear blood flow
• Role of caspases
• Outer haircell plasma membrane fluidity
• Role of glucocorticoid receptors
• Oxidative stress

20. • Shadow effect
• Loudness discomfort level

21. Altmann Group I
• Minor external and middle ear malformation
▫ Auricle normal or with minor abnormality
▫ External auditory canal is normal or with minor
variations
▫ Hypoplastic middle ear
▫ Handle of malleus deformed
▫ Seicircular canal is deformed

22. Altmann Group II
• Moderate external and middle ear malformations
▫ Encompasses majority of ear deformity
▫ Auricle abnormal
▫ EAC – hypoplasia, membranous/ bony, partial/complete
▫ TM – rudimentary
▫ Middle ear- ossicles deformed
▫ Anomalies of auricle (microtia)
 Type I different parts of auricle still recognizable
 Type II auricle represented by vertical edge in normal position
 Type III rudiment of soft tissue , no longer any resemblance to
any portion of auricle

23. Altmann Group III
• Severe external and middle ear malformations
• Pinna- absent
• EAC – aplastic
• Mastoid process – hypoplastic
• Middle ear n antrum absent
• Ossicles- absent
• EAC atresia
▫ UL/BL, Partial/Complete, membranous/osseous
• Ossicular malformations
▫ Abnormalities of malleus/ incus/ stapes
• Ossicles
▫ Absence(partial/complete), Adherence, Attchment
• Facial nerve
▫ Absence of bony canal, Aberrent position

27. • DeaFNess A, B , X
• Various genes
• Wolframin gene – low frq SNHL
• Wolfram s/d – DM, optic atrophy, DI & deafness
• Mutation of CocH gene
• Mid frq- DFNA10

29. Characteristics of sound
• Frequency- rate at which sound fluctuates
• Period- time taken for repetitive fluctuation to repeat
• Wavelength- distance over which its waveform repeats
• Diffraction- way sound bends around obstacles
• Pressure & sound pressure level- strength of sound wave
• Spectrum- break-up of a complex sound into pure tone
components at different frequencies
• Or into several frequency bands (octave, one-third
octave or critical bands)
• Velocity & impedance – degree to which a body of air
vibrates when it is exposed to vibrating sound pressure

30. • AC / BC mechanical hearing aids
▫ AC – hand cupping around the pinna
▫ BC
• Electronic
▫ Vacuum tubes & diodes. Transister instruments
• Electric

31. Components
• Microphone-converts acoustic mechanical
energy into WEAK electrical energy
• Amplifier – converts weak electrical energy into
strong one by increasing voltage
• Receiver – strong electrical energy converted
into mechanical energy

32. Microphone
• Unidirectional
• Omnidirectional
▫ 2 entry ports- front n rear
▫ Rear entry port connected to back of diaphragm via
acoustic delay
▫ Front entry port directly to front of diaphragm
▫ Sound pressure wave approaching from behind will
first enter rear entry port and d acoustic delay before
reaching back face of diaphragm
▫ By this time pressure wave will also enter front port
and will b reaching the front face of diaphragm
▫ Becoz of delay from rear port- 2 pressure waves are in
phase and hence no resultanat pressure

33. Amplifier
• Linear/ Non-linear or compression
• Can represent sound in analogue or digital manner
• Analogue – have waveforms that mimic acoustic
waveforms that they represent
• Digital – represent signal as string of numbers
• Class A, B,D and H. Most efficient is class D.
• Filteres can be used to change relative amplitudes .
Can also b used to break d signal at diff frequency
ranges- so diff aplication can b used for diff
frequency ranges

34. Receiver
• Minature headphones convert amplified
modified electrical signals back to sound energy

35. Feedback
• Feedback – major prob
• Happens when amplification from microphone
to d receiver is greater than the attenuation of
sound leaking from the output back into the
input

36. Compression system in hearing aids
• Decrease the range of sound levels in the
environment to better match the dynamic range
of a hearing impaired person
• May b most active at low, mid or high sound
levels
• Compression threshold- which is the input level
above which the compressor operates is clearly
visible in the diaphragm

37. • Compression ratio- descibes variation in output
level that corresponds to variation in input level
• Simple compression systems-
▫ Input controlled- controlled by signal prior to the
hearing aids vol control
▫ Output controlled- controlled by a signal
subsequent to volume contro

38. Aims of using compressor controls
• Prevent lodness discomfort, hence prevent
distortion
• Increase audibilty of soft syllables by fast acting
compression
• Slow acting compression leaves relative intensities
unchanged but alters overall level speech signal
• More comfortable to wear in noisy ( medium
compression threshold)
• Multi channel compression enables hearing
impaired person to hear sounds of same loudness as
that would be heard by normal hearing persons to
same sounds

39. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
39
Telecoil
• Alternate input source
• Listens to magnetic signal instead
of (or in addition to) the sound.
• Magnetic signal can be from a
telephone, CD, TV, personal ALD,
headphone, loop
• Major advantage is improved
signal to noise
• Usually on BTEs; sometimes on
smaller, seldom on smallest
• You may have to ASK (or
DEMAND) if you want telecoils!
Magnetic
Input
Signal
Sound
Input
Signal
Opinion: Very Valuable

40. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
40
Multiple Microphone Directionality
• Front Facing Directional Mic
• Rear Omnidirectional Mic
• Aid Can Focus on Sounds in
Front and Diminish
Background Noise
• Selectable Modes
▫ Quiet situations: hear
everything
▫ Noisy situations: block
background noise
• Manual or Auto Selection
Opinion: Very Valuable

41. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
41
Compression
0
20
40
60
80
100
quiet loud
Amount of Noise
Amplification
• Reduces Amplificaton
when it’s Noisy
• Helps you hear more
when it’s Quieter
• Keeps it from being
Painful when it’s Noisy
• Adjustable (manual and
automatic)
• Different settings in
multiple frequency
bands
Opinion: Very useful; available
on most aids; may requre
tweaking to set right.

42. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
42
Clipping
0
10
20
30
40
50
60
70
80
90
100
quiet loud
Amount of Noise
Amplification
• Eliminates all
amplificaton above a
certain input
volume
• Prevents hearing
damage from
excessive
amplification in
loud situations
• A setting for most
hearing aids
Normal
Amplification
No Amp-
lification
Opinion: Essential for safety;
available on most aids

43. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
43
Direct Audio Input (DAI)
• Alternate input source
• Listens to electrical signal
instead of (or in addition to)
the sound.
• Electrical signal can be from
a telephone, CD, TV, or
personal ALD
• Major advantage is improved
signal to noise
• Boots available only for BTEs
Opinion: Very good signal;
comparable to FM, but requires
the wires.

44. Introductio
n to
Hearing
Aid
Features
by Steve
Barber,
SHHH
Wake
Chapter
44
Booted or Integrated FM• Some Aids have FM receivers
either booted on (as shown) or
integrated into the aid.
• Some can be used with hand-
held transmitters or with fixed
transmitters which can
integrate TV and Telephone.
• Clean signal; bridges distance;
improves signal to noise ratio.
Opinion: Expensive but wonderful
if you can afford it.

45. Introductio
n to
Hearing
Aid
Features
by Steve
Barber,
HLAA-
Wake
Chapter
45
Bluetooth
• Some Aids have an optional Bluetooth pendant
that use a proprietary magnetic interface.
• Any aids with a telecoils can use a Bluetooth
pendant that uses an analog neckloop.
• Some aids have both (Ask if you want both!)
• Bluetooth has some advantages.
▫ Personal connectivity to TV, Phone, iPods, Tablets
▫ Clean signal; bridges distance; improves signal to
noise ratio.
• Proprietary versions have advantages
▫ True 2-channel stereo
▫ No EMI (interference)
• Bluetooth has some disadvantages:
▫ A bit “techie” for some
▫ Requires a pendant/neckloop
▫ Some delay in audio
▫ Personal: Doesn’t do “broadcast”
Opinion: Not terribly expensive,
and nice to have if you want
that connectivity.

46. Introductio
n to
Hearing
Aid
Features
by Steve
Barber,
HLAA-
Wake
Chapter
46
Programmability
• The ability of an aid to have several different sets of settings
• Hearing aid dealer/audiologist chooses and sets up the programs
• User can switch among the programs
• Examples of useful programs
▫ for quiet situations
▫ for noisy situations
▫ for music
▫ telecoil or DAI with or without microphones
▫ FM
• May be controlled with a switch or button on the aid or with a
remote control
Opinion: Very valuable, but you must understand,
choose and learn how to use the options.

47. Introductio
n to
Hearing
Aid
Features
by Steve
Barber,
HLAA-
Wake
Chapter
47Speech Enhancement and Noise
Reduction
• Speech Enhancement
▫ Enhance certain speech sounds (like consonants)
• Noise Reduction Processing
▫ Identify speech in the signal and separate it from noise
Opinion: May be useful in some situations but these are
not miracles and their benefit may not be obvious in
many situations.

48. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
48
Frequency Shifting
0
10
20
30
40
50
60
70
80
90
100
2k 4k 6k 8k
dB
• Only one aid, so far (AVR
ImpaCT)
• Lowers the frequency of
sounds you can’t hear into a
range where you can hear
them.
• Does some speech
enhancement, too
• With practice those new
sounds start to sound
realistic.
Can Hear Can’t
Hear
Opinion: Most likely useful
for steep ski slopes

49. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
49
Ear Mold Design
• The shape and
smoothness of the bore
• The size and
smoothness of the vent
▫ Too small: Drum Feeling
▫ Too Large: Feedback
• Depth of the mold
• Smoothness of the
adaptor
Vent
Bore
Depth
Adaptor
Opinion: Very important,
and much ovelooked.

50. Introduction to
Hearing Aid
Features by
Steve Barber,
HLAA-Wake
Chapter
50
Open Fitting
• People with mild or
moderate hearing
losses can consider an
“open fitting” instead of
an full ear mold.
• An open fitting is
common on mini-BTE
aids like the one shown.
• Not suitable for more
serious losses.

51. Introductio
n to
Hearing
Aid
Features
by Steve
Barber,
HLAA-
Wake
Chapter
51
Remote Controls
• Let you control your aids
conveniently
• Some simple; some powerful
• Some people like them; some
don’t
• Control:
▫ Volume
▫ Program
▫ Mode
Opinion: Very convenient;
especially if it allows direct
access to individual programs.

52. Styles of Hearing Aids
• Behind the ear (BTE)
• In the ear (ITE)
• In the canal (ITC)
• Completely in the canal (CIC)

53. Binaural hearing aids
• Accurate horizontal localization
• Binaural squelch
▫ In Binaural hearing aids , auditory system can
combine diffenrent mixtures of speech and noise
arriving at each ear to effectively remove some of
the noise
Vertical localization based on HF cues crreated by
pinna- not improved by hearing aids

54. BAHA
• Bone anchored hearing aids
• Consists of titanium screw osseointegrated in
the skull bone behind the ear
• Eligibility
▫ Adequate bone conduction, pure tone thresholds
▫ BC averaged over 0.5,1,2 & 3 kHz should be equal
to or better than 45dB for ear level aid and better
than 58dB for body level aid

55. • Surgery
▫ Complications
 Long term- crusting and inflammation progressing
to granulation tissue
 Osseointegration resulting in screw falling

56. Cochlear Implantation
• Audiological candidacy
• Medical, otological, psychological and Imaging
• Electrode – single or multiple – 4-22
• Incisions
▫ Extended endaural/ Hannover
▫ Inverted U shaped flap
▫ Anteriorly based C shaped incision
complications

57. Middle ear implants
• Partially implantable hearing aids- microphone,
microchip, amplifier and battery externally
• Totally implantable hearing device( Fully
Implanted Middle ear Ossicular Stimulator)
whole unit concealed under skin

58. Vibrant sound bridge
• Surgically implated part- vibrating ossicular
prsothesis (VORP) and an external audio
processor
• VORP is made up of receiving coil, conductor
link and transducer. The transducer emplys a
small electromagnetic coli and enclosed magnet
to produce ibrations I this floating mass
transducer, which is coupled to the long process
of the incus

59. Middle ear transducer (MET)
• Ossicular stimulator
• Fully implantable
• Consists of subcutaneous microphone and
electronic receiver connected to a transducer.
• The transducer drives a proe coupled to body of
incus
• Tip of probe made of aluminium oxide and this
forms a fibrous connection with laser-made hole
in incus body

60. Thanks to the Internet
• For vast resources in terms of pictures and text
material.