Download Auditory Assessment

Auditory Assessment
Bastaninejad, Shahin, MD, ORL-HNS
Assistant Prof., TUMS
Amiralam Hospital
Acknowledgment: I would like to appreciate Prof. Borghei, for preparing this
presentation
CHL
SNHL
Auditory Assessment

Subjective tests
1. Tuning fork tests (TFT)
2. Pure tone audiometry (PTA)
3. Speech audiometry

Objective tests
1.
2.
3.
4.
Impedance audiometry (Tym,AR)
Auditory Brainstem Response (ABR)
Otoacoustic Emission (OAE)
...
Tuning Fork Tests (TFT)
1.
Rinne’s test
2.
Weber’s test
3.
Absolute Bone Conduction (ABC)
Rinne’s Test
Tuning Fork Tests (TFT)




Rinne’s Test
Principal: AC>BC
Rinne +: AC>BC, normal hearing or
sensorineural hearing loss
Rinne -: AC<BC, conductive HL
False Rinne –: unilateral deep
SNHL,
due
to
cross
over
phenomena ,this can be avoided
with masking
Weber’s Test
Tuning Fork Tests (TFT)




Weber’s 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
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
Pure Tone Audiometry (PTA)


It is the graphic record of hearing
Quantitatively & Qualitatively
Pure tones are delivered by headphone 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
Pure Tone Audiometry (PTA)
Pure Tone Audiometry (PTA)
Normal Audiogram
Pure Tone Audiometry (PTA)
Range of hearing loss
Pure Tone Audiometry (PTA)
Conductive Hearing Loss (CHL)
Pure Tone Audiometry (PTA)
Sensori-Neural Hearing Loss (SNHL)
Pure Tone Audiometry (PTA)
Mixed Hearing loss
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
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
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)
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
Impedance Audiometry

Objective test

Includes :
1. Tympanometry
2. Acoustic Reflex
3. External Canal Volume (ECV)
Tympanometry

Record of resistance of conductive
mechanism of ear against pressure
changes of external canal
1. Type A: normal
2. Type B: OME, TM perforation, unfit probe,
middle ear mass
3. Type C: Eustachian tube dysfunction
4. Type As: otosclerosis, tympanosclerosis
5. Type Ad: ossicular dislocation, or Atrophic
TM
6. Type
D:
Scarred
TM,
or
normal
hypermobile TM
Tympanometry
Peak between -100 to +100
Tympanometry
Peak usually in-150 to -200
Tympanometry
Peak is under -300
Tympanometry
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
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
ABR





Surface recording of the electrical
activity of auditory pathway in
response to sound  Sensitive for
Retro-cochlear lesion
Wave
Wave
Wave
Wave
1 & 2: cochlear nerve
3: cochlear nucleus complex
4: Superior olivery complex
5: lateral leminiscus
Middle and
Long
Latency
Response
(MLR,LLR)
Lateral
lemniscus
5th
ABR
3rd
1st and 2nd
4th
Cochlear
nucleus
Sup. Olivary
Complex
ABR
Oto-Acoustic Emission (OAE)
Normal cochlea generate a sound

Due to the biological activity of
outer hair cells
They are of 2 types:

I.
Spontaneous emission (Spont.OAE5070% of people)
II.
Evoked otoacoustic emission