Auditory Assessment

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Auditory Assessment

• Bastaninejad, Shahin, MD, ORL-HNS
• Assistant Prof., TUMS
• Amiralam Hospital
• Acknowledgment I would like to appreciate Prof.
  Borghei, for preparing this presentation

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CHL
SNHL
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Auditory Assessment

• Subjective tests
• Tuning fork tests (TFT)
• Pure tone audiometry (PTA)
• Speech audiometry
• Objective tests
• Impedance audiometry (Tym,AR)
• Auditory Brainstem Response (ABR)
• Otoacoustic Emission (OAE)
• ...

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Tuning Fork Tests (TFT)

1. Rinnes test
2. Webers test
3. Absolute Bone Conduction (ABC)

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Rinnes Test
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Tuning Fork Tests (TFT)

• Rinnes Test
• Principal ACgtBC
• Rinne ACgtBC, normal hearing or sensorineural
  hearing loss
• Rinne - ACltBC, conductive HL
• False Rinne unilateral deep SNHL, due to cross
  over phenomena ,this can be avoided with masking

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Webers Test
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Tuning Fork Tests (TFT)

• Webers Test
• Principal compares the BC of the two ears
• Normal hears equal on both sides or does not
  hear at all
• Conductive HL lateralized to the more affected
  side
• SNHL lateralized to the less affected side

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Tuning Fork Tests (TFT)

• Absolute Bone Conduction test
• (Schwabach test)
• Compares the BC of the examiner with the patient
• Normal equal to the examiner
• CHL longer than the examiner
• SNHL less than the examiner

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Pure Tone Audiometry (PTA)

• It is the graphic record of hearing
  Quantitatively Qualitatively
• Pure tones are delivered by head-phone for AC
  by a vibrator for BC
• X-Axis Frequency range 125 12000 Htz
  (routinely depicted from 250-8000 Htz)
• Y-Axis Intensity of sound in decibels (dB)
• A decibel is the smallest change in the intensity
  of sound which can be recognized by normal human
  ear

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Pure Tone Audiometry (PTA)
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Pure Tone Audiometry (PTA)

• Normal Audiogram

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Pure Tone Audiometry (PTA)

• Range of hearing loss

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Pure Tone Audiometry (PTA)
Conductive Hearing Loss (CHL)
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Pure Tone Audiometry (PTA)
Sensori-Neural Hearing Loss (SNHL)
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Pure Tone Audiometry (PTA)
Mixed Hearing loss
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Masking

• To prevent crossover phenomena
• Crossover happens with
• 40-60 dB AC difference in two ears
• 0-20 dB BC difference in two ears
• Masking problem
• Masking dilemma in bilateral CHL or Bilateral
  Mixed HL
• Overmasking ? masking noise crosses over to the
  other side

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Speech Audiometry

• Recorded voice is used
• Speech Detection threshold(SDT)
• An intensity level at which a listener can barely
  discern the presence of a speech signal in 50 of
  the time
• It is equal to the PTA average obtained at
  500,1000,2000Hz

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• Speech Reception Threshold (SRT)
• Two syllabus words (Spondee)
• With different intensities
• The intensity at which 50 of the presented words
  can be repeated
• Measured in dB (it is usually 8-9dB more than
  SDT)

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Speech Audiometry

• Speech Discrimination Score (SDS)
• Mono syllable words
• At 50dB higher than SRT
• Percentage of words recognized correctly is
  noted
• Normal 96-100
• CHL 90-100
• SNHL low
• Retro cochlear very low

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Impedance Audiometry

• Objective test
• Includes
• Tympanometry
• Acoustic Reflex
• External Canal Volume (ECV)

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Tympanometry

• Record of resistance of conductive mechanism of
  ear against pressure changes of external canal
• Type A normal
• Type B OME, TM perforation, unfit probe, middle
  ear mass
• Type C Eustachian tube dysfunction
• Type As otosclerosis, tympanosclerosis
• Type Ad ossicular dislocation, or Atrophic TM
• Type D Scarred TM, or normal hypermobile TM

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Tympanometry
Peak between -100 to 100
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Tympanometry
Peak usually in-150 to -200
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Tympanometry
Peak is under -300
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Tympanometry
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Acoustic Reflex

• Stapedial muscle contraction in response to loud
  noise
• 70-100 dB above hearing threshold
• Particularly useful for DDx between Cochlear and
  Retrocochlear lesions
• Afferent cochlear (8th) nerve
• Efferent facial (7th)nerve

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Acoustic Reflex

• Absent bilaterally when tested ear has CHL
• BC must be better than 60dB to elicit this reflex
• AR negative in tested ear but in the
  contralateral ? Retrocochlear lesion
• AR Positive in Ipsi., but negative in Contra.?
  Brain Stem lesion
• It also demonstrate level of facial nerve lesion

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ABR

• Surface recording of the electrical activity of
  auditory pathway in response to sound ? Sensitive
  for Retro-cochlear lesion
• Wave 1 2 cochlear nerve
• Wave 3 cochlear nucleus complex
• Wave 4 Superior olivery complex
• Wave 5 lateral leminiscus

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Middle and Long Latency Response (MLR,LLR)
Lateral lemniscus
5th
Cochlear nucleus
ABR
3rd
4th
Sup. Olivary Complex
1st and 2nd
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ABR
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Oto-Acoustic Emission (OAE)

• Normal cochlea generate a sound Due to the
  biological activity of outer hair cells
• They are of 2 types
• Spontaneous emission (Spont.OAE?50-70 of people)
  
• Evoked otoacoustic emission

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Any Question!?