Paediatric Audiology - Untitled by hjkuiw354

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									 Paediatric Audiology




Introduction To:
 Audiograms
 Tympanometry
 Hearing Loss Management




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              Audiograms




Audiograms
Audiograms show hearing acuity and hearing levels are
referred to as thresholds

Frequency is expressed in Hertz (Hz) and is perceived as
pitch

Intensity represents the physical energy generated by a
signal and is expressed in decibels




                 20 log     pressure output
                            pressure reference




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    The Speech Spectrum
Significant hearing
loss is determined on
the basis of how
accessible the speech
sounds are to the
child

Significant hearing
loss is generally
defined as bilateral
thresholds of
greater than 40dB




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Audiogram Key
 Air conduction thresholds
 Right - O    Left - X     Binaural (FF) -

 Bone conduction thresholds
 Right - [   Left - ]    Binaural -

 Aided Thresholds
 Right - H   Left - V     Binaural -




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 Conductive Hearing Loss

                                Mild
                                Bilateral




Maximum Conductive Hearing Loss = 60dB




    Moderate                Profound
    Bilateral               Bilateral
    Conductive              Mixed




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Conductive Hearing Loss
Ear Canal
OBSTRUCTION OF SOUND PATHWAY:
 Otitis externa
 Haemangiomas
 Wax occlusion
 Inserted objects
 Deformed ear canal - atresia




Conductive Hearing Loss
Middle Ear
 Glue ear
 Eustachian tube dysfunction
 Tympanic membrane problems
           * Tympanosclerosis
           * Perforations
 Chronic infection – Cholesteatoma
 Ossicular Chain problems
           * Sclerosis
           * Discontinuity




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Sensorineural Hearing Loss
                                     Mild
                                     Bilateral




Sensorineural Hearing Loss
 Incidence of 1 : 1000 live births

 Babies admitted to NICU increases the risk
 of S/N loss by 10 to 20%




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Sensorineural Hearing Loss
Risk Factors
 Family history of deafness
 Congenital deformities
 Ante-natal infections
 Peri and post-natal infections
 Low birth weight ( < 1500gms )
 Hyperbilirubinaemia
 ( exchange transfusion level )
 Severe cerebral hypoxia
 Ototoxic drugs




 Mixed Hearing Loss
                                  Moderate
                                  Bilateral




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       Tympanometry




Tympanometry
Measure how efficient the transfer of sound
energy through the middle ear system

Apply negative and positive air pressure on the
T.M. while monitoring a constant tone in the ear
canal indirectly measures how compliant the
middle ear system is to sound

Arrive at 3 different traces (Tympanograms)
which indicate the state of the middle ear




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Tympanometry




               10
Tympanograms
Type (A)
 “Normal” middle ear function

 Rules out the presence of most conductive
 hearing loss

 Most consistent with normal thresholds or
 a sensorineural hearing loss




Type (A) Tympanogram




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  Tympanometry
  Type (B)
   Middle ear pathology indicated
        * Glue ear
        * T.M. perforation
        * Wax occlusion
        * Ear canal stenosis

   Would expect a conductive component to
   the audiogram ranging from mild to
   moderate




Type (B)
Tympanogram




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Tympanometry
Type (C)
 Eustachian tube dysfunction

 May result in a mild low to mid tone
 conductive hearing loss

 Would not expect a significant speech
 delay




  Type (C) Tympanogram




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Tympanometry
Neonates 0-6mths age
      Conventional low frequency probe tone
      testing (226Hz.) is not reliable with this
      age group

      Results have shown:
1.    False negatives (type A = type B tymp.)
2.    False positives (type B = type A tymp.)




 Tympanometry
 Neonates:0-6mths age
     Otoscopy and surgical examination have
     shown that using a 1000Hz. probe tone
     frequency gives reliable tympanogram
     traces.

     NB: Studies of high frequency probe tone
     tympanometry have only investigated
     middle ear effusion – other pathologies can
     not be commented on at this stage




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    Tympanometry
    Neonates: 0-6mths age

   Low frequency probe tone is thought to
   be ineffective in this age group due to
   maturational reasons




Tympanometry
Neonates: 0-6mths age
Physical Changes:
1. Increase in size of the external ear,
   middle ear cavity and mastoid
2. Changes in the orientation of the T.M.
3. Fusion of the Tympanic ring
4. Tightening of the ossicular joints
5. Closer coupling of the of the stapes to the
   annular ligament
6. Formation of the bony ear canal




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Audiogram Interpretation




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17
18
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Freefield Testing : To rule out an
overall hearing loss
Minimum Levels
 Test to 20 dB

Acceptable Levels
  30 to 40 dB – but
  important to review
  hearing later on




               Case: B.M.




                                     20
                Case: B.M.




                           Freefield Testing

What does this audiogram
show?
How would you manage
this case if:
(1)Type(A) tympanograms
(2)Type(B) tympanograms




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                Left Ear Canal Atresia


How would you
manage this
case?




 Desferal – Thalasaemia Major




                                         22
Tobramycin – Cystic Fibrosis




     Cisplatin - Oncology




                               23
     Alports Nephritis




Hearing Loss Management




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     Audiological Management
     Referrals received from UNHS
     regarding diagnosed hearing loss would
     fall into 3 main categories:

1.   Bilateral minimal loss or unilateral loss
2.   Bilateral moderate to severe loss
3.   Bilateral severe to profound loss

     Each category requires a different
     management approach




 Oto Acoustic Emissions

 Test of peripheral
 hearing to the level
 of the Outer Hair
 Cells in the Cochlea




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     A-ABR: Automated Auditory
     Brainstem Response


Tests the auditory
pathway to the of the
level of the brainstem




  Audiological Management

 Bilateral minimal
 losses can be defined as
  a loss of up to 40dB

  Results gained through a
  diagnostic ABR would
  show hearing thresholds of
  20 to 30dB or 30 to 40dB
  determined by using a
  broadband click stimulus




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Audiological Management
Bilateral Mild losses up to 40dB
 Hesitant to amplify - baby 1-1 hears speech well
 Monitor and define hearing behaviourally
 Monitor speech and language development
 With speech delays perform assessments to rule out
 speech specific problems eg dyspraxia
 May need amplification in demanding listening
 environments eg classroom




  Audiological Management

  Unilateral Loss can be defined as a
   significant loss in one ear (equal to or
   greater than 40dB) and normal thresholds
   in the contralateral ear




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     Audiological Management
     Unilateral Losses
      Generally do not refer for amplification
      If problems occur with learning at school
      then consider:
1.    Improving the classroom acoustics
2.    Trialling a sound field or personal FM
      system
      If no success with above alternatives
      consider a hearing aid on a trial basis




 Case: ZG Minimal Losses
 Born 24 weeks gestation,490gms
 A-ABR at 3 months age
 Result – Bilateral refer

 Diagnostic ABR at 4 months age
 Result
   Right – 20-30 response to click stimulus
   Left – 40-50 response to click stimulus
   Tympanometry did not indicate middle ear
   pathology (226Hz)




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Case: ZG
BOA at 12 months (corrected age)

 Responded at minimum intensity levels of
 35-40 dB, good localisation abilities
 Babbling well and generally responding
 well to sound
 Normal Tympanometry




                        Case:ZG
VROA at 18 months
 (corrected)

 Tympanometry
 indicated middle ear
 fluid bilaterally

 Speech developing:
 Beginning to say
 some single words




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                            Case:ZG
Repeat VROA at 22
months (corrected age)
after grommet
insertion

Tympanometry:
 L - Patent Grommet
 (ABR- 40-50)

R - Non patent grommet
& middle ear fluid
(ABR- 20-30)




                            Case:ZG
Headphone testing
3years of age

Speech is normal for age

Tympanograms
consistent with bilateral
middle ear fluid

Bone conduction
suggests normal
thresholds




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                        Case: ZG


3.5 years age
post grommet
revision shows
normal hearing




  Minimal Losses in Neonates
  Audiological Management
     Minimal losses can take some time to accurately
     define in very young children

     It is important to monitor the child’s progress
     especially in the areas of speech and language
     development

     Amplification for minimal losses based only on
     electrophysiological test results should be
     approached with caution




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     Audiological Management
     Bilateral Moderate
     to Severe losses can
     be defined as having
     hearing thresholds
     ranging from 45dB to 85
     dB across the audiogram
     frequency range




Audiological Management
Bilateral Moderate to Severe Losses
(Fitting of Hearing Aids 3 mths. age)

       ENT clearance for hearing aid fitting
       Monitor hearing over time
1.     Unaided
2.     Aided - detection of speech
             - speech perception




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Medically Related Contraindications to a
Hearing Aid Fitting
  Situations Requiring Investigation in order to
  identify cause of problem and to rule out retro-
  cochlea pathology
  A hearing loss of sudden onset
  A rapid progressing hearing loss
  Pain in either ear
  Tinnitus: of sudden recent onset or unilateral
  tinnitus
  Unilateral or markedly asymmetrical hearing loss of
  unknown origin
  Vertigo
  Headaches
  Fluctuating hearing loss




 Audiological Management
Bilateral Severe to
Profound Losses can
be defined as thresholds
ranging from 70dB to
120dB across the
audiogram frequency
range




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     Audiological Management
     Bilateral Severe to Profound losses
     Urgent fitting of hearing aids
     (by 3 months age)

     Referral to Cochlear Implant Program
     Assess /Address middle ear involvement
     SSEP
1.   to define amount of residual hearing
2.   to optimise the hearing aid fitting




     Audiological Management

     Bilateral Severe to Profound Losses
     Assess potential to develop speech through
     aided testing

     Intensive Aided Evaluation from 7 months
     age to determine candidacy for Cochlear
     Implantation
     Arrive at a recommendation regarding
     Cochlear Implantation by the age of 9mths
     age given no complicating factors eg global
     developmental delay




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Medical Contraindications for
Cochlear Implant Surgery
Chronic otitis media
Cochlea ossification
Cochlea deformities – Mondini
Absent cochlea and/or auditory nerve
Child is unable to undergo surgery due to
poor health / complicating factors eg cardiac
problems – Noonan’s Syndrome




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