Audiology Testing & Principles

Question 1

Describe Interaural attenuation. What levels of attenuation can be achieved by bone conduction, headphones and insert ear phones?

Answer 1

Interaural attenuation: The reduction in sound intensity as it travels from one ear to the other. The degree of interaural attenuation varies depending on how sound is presented, and is used to determine when masking is needed.

Bone conduction: 0dB (all sound needs to be masked)
Over the head earphones: 35-50dB attenuated
Insert ehadphones: ~60-65dB attenuated

Greater interaural attenuation occurs at higher frequencies

Question 2

Define crossover

Answer 2

Crossover occurs when a sound volume exceeds the interaural attenuation with a given test device and then crosses over from the test ear to the non-test ear

Question 3

√What are five characteristics of the decibel scale?

Answer 3

1. Non-linear
2. Logarithmic scale
3. Relative measure
4. Incorporates a ratio
5. Expressed with different reference levels

Question 4

√What is masking?

Answer 4

Making is required when you would expect to experience crossover.

In order to ensure thresholds are from the test ear, a sound stimulus is presented to the non-test ear in order to overcome crossover. Narrow band noise used for pure tongues, and speech noise for speech signals.

This is ALWAYS REQUIRED FOR ANY BC TESTING because interaural attenutation with BC is 0.

Masking with air conduction varies depending on the type of headphone (supraaural or insert), the model, and the volume presented).

Masking signal to the non-test ear is via AC, and if crossover occurs, the sound is perceived on the non-test ear as BC.

Question 5

Describe the general principles of when masking is required3.
What is the initial masking level?

Answer 5

When testing air conduction:
- AC masking is required if the test ear AC exceeds non-test ear BC by 40 (supra-aural) or 50 (inserts) dB. (AC TE - BC NTE = 40-50)
- Initial masking level = AC threshold of NTE + 5dB (minimal effective masking correction) + 10dB (safety factor)

When testing bone conduction:
- BC masking required if air-bone gap of test is ear >0 (some say 10dB) (AC TE - BC TE = 0-10)
- OR when BC of test ear exceeds non-test ear by 10dB (BC TE - BC NTE = 10)

Question 6

What is the masking dilemma? How can this be over come?

Answer 6

Seen in patients with large bilateral conductive hearing loss, when enough masking it too much - when both AC thresholds approach the level of interaural attenuation (~40dB - bilateral air bone gaps 40-50). In these cases, the amount of masking needed to mask the test ear (which is high because of the conductive hearing loss) will exceed the interaural attenuation and then cross back over to the test ear. This will inadvertently mask the test signal, and the non-test ear can not be masked because any masking sound that will be loud enough to exceed the interaural attenuation will still cross over.

Can be mitigated with insert earphones (have a larger interaural attenuation). If CHL still exceeds this, then it will be marked as “could not mask”

Question 7

Go through scenarios of masking and non-masking

Answer 7

Kevan’s notes page 14

Question 8

√What is a decibel?

Answer 8

Bel = Unit of sound intensity relative to a reference intensity. Intensity is related to the perception of loudness

• Unit to express intensity of sound; Specifically, the logarithm of the ratio of two sound intensities. Decibel is One-tenth of a Bel
• Ratio may be power, sound pressure, voltage, or intensity
• For audiometry, the decibel refers to sound pressure

Bel = log10 (Is/Ir) - Sound intensity / Reference intensity (reference intensity dependent on the dB scale being used)

Decibel dB = 10Log10 (Is/Ir)

Intensity level - Magnitude of sound. Sound pressure (pascals) is proportional to the square root of intensity and therefore when substituting pressure into the formula it needs to be squared - dB = 10log10(Ps/Pr)^2 = 20log10(Ps/Pr)

Sound pressure dB = 20log (Ps/Pr)
Pr = sound pressure level at 20µPa

Question 9

√How many times louder is 60dB vs. 0dB? What about 60dB vs. 40dB?

Answer 9

60 vs 0:
dB = 10 log10 (Is/Ir)
60=10log10(Is/Ir)
Is/Ir = 10^6 = 1 000 000 times louder

60 vs 40:
dB = 10 log10 (Is/Ir)
60-40=10log10(Is/Ir)
20=10log10(Is/Ir)
Is/Ir = 10^2 = 100 times louder

See Vancouver notes 224

Question 10

√Define the following terms:
dB SPL
dB HL
dB nHL
dB SL

Answer 10

dB = 10log10 (Is/Ir) (sound intensity/reference intensity)

dB SPL = dB Sound Pressure Level
- Most common measure of sound
- Amount of sound pressure that is produced at a given frequency (pressure to move the TM), also a logarithmic ratio
- Values are all normalized against a reference sound pressure level (20microPascal, or 0.01mPa = 0dB)
- Used for tympanometry and stapedial reflexes

dB HL = dB Hearing Level
- Not all sound pressures are equally loud
- Human ear does not respond equally to all frequencies - much more sensitive to sounds in the frequency range about 1kHz to 7kHz than to very low or high frequency sounds
- Audiometric test tones are therefore specified as hearing level (HL) rather than SPL, because normal ear is not sensitive to the SPL ranges
- In dB HL, the baseline reference is calibrated to the threshold sound pressure that can be heard in normal patients with normal hearing at each frequency
- 0dB HL is least intensity for the average normal ear to perceive a specific frequency 50% of the time
- Image: Notice that low and high frequencies need higher sound pressure to be audible, while 1kHz to 7kHz is the most sensitive and have the least amount of pressure to create audible sound. These sound pressures can then be normalized and converted at each level to a hearing level.

dB nHL = dB Normal Hearing Level
- A decibel scale used in ABR measurement referenced to average behavioural threshold for the click stimulus of a small group of normal-hearing subjects

dB SL = dB Sensation Level
- Another way to refer to stimulus intensity. It’s reference (denominator) is the threshold (hearing level) of the individual being tested
- E.g. 30dBSL means 30dB above that individual’s threshold for the test stimulus. If the PTA is 30dB HL, then a stimulus presented at 70db HL = 40dB SL.
- dBSL will often be used to specify the level at which speech discrimination tests (SDT) are administered. For example, if an individual’s speech reception threshold (SRT) is 40dBHL, a SDT administered at 30dBSL is given at a hearing level of 70dBHL. If SRT was 10dBHL, the SDT would have to be given at 40dBHL to meet the condition of a 30dBSL presentation
- Each human has different pressure levels for the same frequencies. Therefore each frequency is mathematically normalized to a similar baseline of “0dB SPL”.

https://entokey.com/wp-content/uploads/2016/06/9781604063585_c001_f001.jpg

Audiology half day notes

Question 11

What frequency do humans hear best at?

Answer 11

Between 500Hz - 4000Hz

Question 12

√What is the reference level for SPL, HL, and SL?

Answer 12

SPL: Reference sound pressure level of 20 microPa
HL: Reference is the threshold sound pressure that can be heard in normal patients with normal hearing at each frequency
SL: Referenced against patient’s specific hearing thresholds (HL)

Question 13

√How many decibels is required to double sound energy?

Answer 13

3dB IL or 6dB SPL

Question 14

Describe the degrees of hearing loss with respect to dB level

Answer 14

Normal: 0-25dB
Mild: 25-40dB
Moderate: 40-55dB
Moderate-Severe: 55-70dB
Severe: 70-90dB
Profound: >90dB

Pediatrics - “slight hearing loss” - 15-25dB, as there are quieter cues that are important for speech and language development at this age

Question 15

What are the symbols used on an audiogram?
Red
O
Triangle
<
[
Blue
X
Square
>
]
S
Down left arrow
Down right arrow

Answer 15

Right ear:
- RIGHT = RED = ROUND
- O = Unmasked air conduction
- Triangle = Masked air conduction
- < = Unmasked bone conduction
- [ = masked bone conduction
- Down left arrow = no response

Left ear:
- BLUE
- X = Unmasked air conduction
- Square = Masked air conduction
- > = unmasked bone conduction
- ] = masked bone conduction
- Down right arrow = no response

S = sound-field

Question 16

Interpretation of tuning fork exam

Answer 16

Weber:
- Ipsilateral - CHL
- Contralateral - SNHL

Rinne:
- AC > BC = Normal
- BC > AC = SNHL
- BC (opposite ear) = SNHL ipsilateral

Question 17

Why does Weber lateralize to the ipsilateral ear in CHL?

Answer 17

Mechanism not well understood, but generally 2 proposed mechanisms:

1. Release from masking in the ear with the conductive loss (conductive loss masks the sound) - wounds from the surrounding world cannot mask the tuning fork tone, therefore still goes to the good ear
2. Sound is not allowed to filter out through the ossicular chain/TM/EAC, therefore BC when doing Weber is perceived as louder in this ear

Question 18

Discuss the Pure Tone test Procedure

Answer 18

Threshold of hearing is defined as 2 out of 3 (or 3 out of 5) correct responses during the ascending portion of the tone presentation.

If patient responds when tone is ascending, test will decrease level by 10dB.

Intensity increase will be in steps of 5dB, and decrease will be in steps of 10dB

Question 19

What are the frequencies tested on Pure Tone Audiometry?

Answer 19

125Hz lowest
Octaves - 250, 500, 1000, 2000, 4000, 8000

1000 is the most important single frequency

Conventional speech ~65 dB SPL
Autophony ~85 dB SPL

Question 20

Define Pure Tone Average (PTA)

Answer 20

Average of the pure tone thresholds at 500, 1000, and 2000 Hz

Note: Per Baileys, can also use 3000Hz but some centres that don’t use 3000 can include 2K and 4K into average

Question 21

At what dB HL level are vibrotactile responses experienced at for air conduction and bone conduction?

Answer 21

Air Conduction
- 90dBHL @ 250Hz
- 110 dBHL @ 500 & 1000 Hz

Bone Conduction:
- 30-35dBHL @ 250Hz
- 55dBHL @ 500Hz
- 65-70dBHL @ 1000 Hz

Question 22

What is 6 differential diagnosis of a flat hearing loss?

Answer 22

1. Late Meniere’s
2. Ototoxicity (macrolides)
3. Otosyphillis
4. Presbycusis (strial/metabolic & neural types)
5. Sudden SNHL
6. Vascular Loop (vascular compression of CNs)

“LOOPS” - Vascular Loop, then LOOPS mnemonic

Question 23

What is 8 differential diagnosis for a sloping (high frequency) hearing loss?

Answer 23

1. Sudden SNHL
2. Ototoxicity (cisplatin, aminoglycosides)
3. Vestibular Schwannoma
4. Presbycusis (sensory & cochlear conductive types)
5. Diabetes
6. Herpes Zoster Oticus
7. MS
8. Vascular loop

Question 24

What is 4 differential for reverse-sloping (rising, or low frequency) hearing loss?

Answer 24

1. Early Meniere’s
2. Otosclerosis
3. SCDS
4. Sudden SNHL

Question 25

What id 3 differential of a cookie-bite hearing loss (mid-range hearing loss, U-shaped)?

Answer 25

1. Hereditary 2. Cochlear Otosclerosis 3. Congenital Rubella

Question 26

What is 2 differential for reverse-cookie bite (tenting) hearing loss?

Answer 26

1. Meneire's 2. Cogan Syndrome (bilateral)

Question 27

Define Speech Detection Threshold (SDT) vs. Speech Recognition Threshold (SRT)

Answer 27

SDT: The minimum sound threshold needed at which speech is discernable 50% of the time (can recognize presence of speech signal with spondee words). Patients not required to repeat the word back; used when patients don't speech English or mentally handicapped and cannot repeat words back (not a routine test). SRT: The minimum sound threshold at which at least 50% of words are understandable (have to repeat them back). Words are taken from a library of spondees (2 syllable words with equal stress on each syllable). Correlates to the PTA - agreement between PTA & SRT should be within 5-10dB HL

Question 28

Define Spondee

Answer 28

Two syllable words with equal emphasis on both syllables, that are used to determine the speech recognition threshold. E.g. Sunset, bookmark, baseball, earthquake

Question 29

Define Speech/Word Discrimination Score (SDS/WDS) or Word Recognition Score (WRS)

Answer 29

Percentage of correct words identified from a phonetically balanced word list (a collection of words matching the phoneme distribution in the english language). Can be an open set (open response) or closed set (closed response - given possible options for each word like multiple choice) Words are presented at 30-50dB above a patient's SRT which should be easily audible. Useful to determine functional ability to hear and understand speech. SDS + PTA should be > 100. If < 100, concern for retrocochlear pathology E.g. 25 or 50 word library

Question 30

Define Phonetically balanced word list

Answer 30

50 single syllable words which contains the same proportion of phonemes as that which occurs in connected american english discourse Phoneme = phonetically distinct unit of sound in a language to distinguish words apart. E.g. Boat, pool, mode, fat

Question 31

What is involved in an entire audiologic test battery?

Answer 31

Hearing acuity - air conduction and bone conduction thresholds Speech testing - SDT, SRT, Speech recognition, subjective report scales.

Question 32

What is the minimum speech test battery (MSTB)?

Answer 32

Used for adult speech testing for CI Candidacy. Involves 3 tests: 1. CNC Word Test (10 lists of 50 words) - Administration of consonant-nucleus-consonant monosyllabic words (e.g. cat, dog, rat). 2. AzBio Sentences (8 lists of 20 sentences) - Setences developed by the Arizona Biomedical Institute 3. BKB-SIN test - Bamford-Kowal-Bench Speech-in-noise - Test of hearing in noise function

Question 33

What are immitance tests? What are two common types of immitance tests?

Answer 33

Immittance Tests: Measure of how readily the middle ear system can be set into vibration by a driving force Immittance = admittance + impedance Admittance - total energy flow through the system Impedance - total opposition to energy flow or resistance to the absorption of energy 1. Tympanometry: Measures acoustic immittance of the TM and middle ear ossicular chain as a function of air pressure variations in the ear canal. Estimates intratympanic pressure, ET function, TM integrity and mobility, and continuity of the ossicular chain. 2. Stapedial Reflexes: Determines the softest level of sound that will elicit stapedial muscle contraction. Typically occurs at 70-100dB HL for normal hearing ear (ie. 70-100dB SL) 3. Acoustic reflex Decay: Measures the ability of the stapedius muscle to maintain sustained contraction. A response is abnormal if its amplitude decreases to half or less of its original measurement over 5-10 seconds (time varies depending what you read)

Question 34

What are the normal ear volumes for the EAC, middle ear, mastoid, bony labyrinth, membranous labyrinth?

Answer 34

EAC: Children - 0.5-1mL Adults - 0.6-2mL (N~1.4 cm^3) Middle ear - 0.5-1cm^3 Mastoid - 2-20cm^3 Bony Labyrinth - 0.2cm^3 Membranous Labyrinth - 0.04cm^3

Question 35

Describe the Stapedial Reflex Pathway

Answer 35

Reflex pathway that is triggered in response to a loud noise, causes tensing of the stapedius muscle (inserts onto stapes) which dampens sound transmission across the oval window. Thought to be protective mechanism against noise induced injury. Pathway: Sound --> Cochlea (afferent pathway) --> Vestibulocochlear nerve CNVIII --> Ventral Cochlear Nucleus --> Trapezoid body within the medial superior olivary complex (1st region to receive bilateral info - travels to bilateral bodies) --> Facial motor nucleus (efferent pathway) --> Facial nerve --> Nerve to stapedius --> Stapedius muscle Measured by looking at changes in TM compliance (with similar probe) caused by contraction of the stapedius muscle

Question 36

Define Acoustic Reflex Threshold (ART) vs. Acoustic Reflex Decay

Answer 36

Acoustic Reflex Threshold: Softest sound level that elicits stapedial contraction (normal = 70-100dB) Acoustic Reflex Decay: Inability of stapedial muscle to maintain contraction for 10 seconds with sound presented at 10dB above ART

Question 37

What are possible test results for the acoustic reflex?

Answer 37

Normal: Present reflexes at normal sound levels, and sustained x 10 seconds at ART Elevated: Requires more sound to elicit response Decay: A response is abnormal if its amplitude decreases to half or less of its original measurement over 5 seconds Absent: No response. Either due to afferent issue (sound isn't transmitted to inner ear) or efferent issue (can't trigger stapedial response or measure it due to middle ear pathology) Diphasic: Increased compliance at the onset, and cessation of the sound stimulus (?) ## Footnote https://www.interacoustics.com/images/guides/tympanometry/reflex-measurement/reflex9.png

Question 38

Describe what the stapedial reflex findings would be for right ipsi, right contra, left ipsi, and left contra for the following clinical scenarios: Right cochlear problem Right CNVII problem Right ME problem Small central brainstem lesion affecting crossing fibers Large central brainstem lesion

Answer 38

Right cochlear problem: - Right ipsi: elevated/absent - Right contra: elevated/absent - Left ipsi: normal - Left contra: normal Right CNVII problem: - Right Ipsi: elevated/absent - Right contra: normal - Left ipsi: normal - Left contra: elevated/absent Right ME problem: - Right ipsi: elevated/absent - Right contra: elevated/absent - Left ipsi: normal - Left contra: elevated/absent Small central brainstem lesion affecting crossing fibers: - Right ipsi: normal - Right contra: absent - Left ipsi: normal - Left contra: absent Large central brainstem lesion: Absent everywhere bilateral ipsi/contra

Question 39

Name 6 conditions that may demonstrate absent stapedial reflexes bilaterally

Answer 39

1. CHL > 40dB in test ear 2. SNHL > 70-80dB in test ear 3. Bilateral VII lesions 4. Bilateral VIII lesions (e.g. NF2) 5. Brainstem lesion 6. Multiple Sclerosis ## Footnote 1 and 2 Sound not loud enough to stimulate the reflex Reason SNHL is higher threshold is because lots of patients with SNHL have hyperacusis so they have lower threshold for louder sounds, so don’t need as much loudness to trigger the reflex

Question 40

Describe how to draw a tympanogram

Answer 40

X-axis: Air pressure (in daPa or mmH2O) from -400 to +200 (in increments 100) Y-axis: Immitance (compliance) in mmho (volume) from 0 to 1.5 (up in increments of 0.3) ## Footnote See Vancouver notes page 227

Question 41

Describe the differential for each Jerger Tympanogram 2 each

Answer 41

Type A: Normal Type As (shallow/stiff): - Otosclerosis - Tympanosclerosis with fixation Type Ad (deep or discontinuity): - Ossicular chain discontinuity - Large monomeric drum Type B (flat): - Middle ear effusion - TM perforation - Seal hitting against EAC - Foreign body/Cerumen Type C (negative): - Eustachian tube dysfunction Type D (notched) - Scarred TM (two pressures produced)

Question 42

Describe how you would draw each tympanogram

Answer 42

Type A: - Peak between ± 100daPa - Compliance 0.3-1.5mL Type As: - Peak between ± 100daPa - Compliance < 0.3mL Type Ad: - Peak between ± 100daPa - Compliance >1.5mL Type B: - No peak, flat Type C: - Peak at < -100daPa - Compliance 0.3-1.5mL Type D: - Notch at the peak

Question 43

What are the parts of a tympanometer? 4 How does this change in infants?

Answer 43

1. Pump 2. Manometer (records pressure) 3. Speaker (226Hz SPL @ 65-70dB) - 226Hz may produce false negative (false normal) in infants/neonates under 6 months (ear canal very soft and therefore may also move in response to pressure) --> use either 660 or 1000Hz 4. Microphone

Question 44

What frequencies should you use to test for tympanometry?

Answer 44

226Hz for age > 6 months 1000Hz (or 660) for < 6 months

Question 45

Where is the peak division for Type A vs. Type C tympanogram

Answer 45

-100 daPa (mmH2O)

Question 46

What are the 3 conditions in order to elicit stapedial reflex?

Answer 46

1. Loud enough stimulus 2. Normal middle ear function 3. Normal reflex arc (pathway and muscle function)

Question 47

What are the stapedial reflex hearing loss thresholds?

Answer 47

< 50dB SNHL - Normal stapes reflex threshold (reflex requires >50dB, therefore mild-moderate losses are not affected 50-65dB SNHL - Elevated stapes reflex threshold >65dB SNHL - Likely no reflex VIII - losses associated with reflex decay, and likely absent reflex (retrocochlear) CHL > ~40dB on test ear; ± absent on contralateral side 25-40dB (due to bilateral pathway)

Question 48

What are the stapedial reflex threshold differences using pure tones vs. broadband noise?

Answer 48

Broadband noise has 20-25dB lower thresholds compared to pure tones. This difference lessens as hearing worsens.

Question 49

At what frequencies does the stapedial reflex get tested?

Answer 49

Usually measured at 500, 1000, and 2000 Hz Normally occurs at 70-dB SL for pure tones

Question 50

What is the latency of the stapedial reflex testing?

Answer 50

10ms - therefore will not protect cochlea from unanticipated sounds

Question 51

What is the incidence of absent stapedial reflex? What is the incidence of absent stapedius tendon, muscle and pyramidal eminence?

Answer 51

Absent reflex = 10% Absent tendon and muscle and PE = 1%

Question 52

Describe the Reflex Decay Test

Answer 52

Measured at 500 or 1000Hz, 10dB above stapedial reflex threshold for 10 seconds (~100dB) Abnormal Decay = failure to maintain 50% of original amplitude over 10 seconds. Indicates probable retrocochlear lesion (CNVIII or brainstem)

Question 53

Define Rollover. What is rollover index to suggest retrocochlear pathology and how is it measured?

Answer 53

A paradoxical decrease in discriminal ability (SDS) with increasing signal intensity. Suggests retrocochlear pathology. Other definitions: Decrease in SDS by more than 12-20% as the presentation level is Increased PIPB = performance intensity function using phonetically balanced words Rollover index = (Pbmax - Pbmin)/Pbmax > 0.40 is suggestive of retrocochlear pathology (strong dip in PB performance) --- Performance Intensity Function of Phonetically Balanced Words (PIPB test) * Phonetically balanced "PB" word lists are presented in 10-20dB steps above the SRT * Scores should improve with increases in intensity * PB scores improve until a maximal score (PB Max) is obtained at which point the score does not change significantly with further increases in intensity * Scores are not expected to change more than 19% once PB max is reached * As presentation levels are increased in an individual with a retro-cochlear lesion, reduced speech discrimination scores (greater than 20dB change, after PB max) are obtained ◦ Situation is termed the "rollover" phenomenon ## Footnote See my own royal college notes for details - Royal College folder --> Notability notes to print --> Otology chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://vula.uct.ac.za/access/content/group/27b5cb1b-1b65-4280-9437-a9898ddd4c40/Speech%20Audiometry.pdf

Question 54

What is recruitment in Audiology?

Answer 54

A phenomenon where increasing sound intensity (dB) produces an out of proportion perception of loudness, and typically suggests cochlear hearing loss. Clinically seen as patients who say "talk louder" followed by "stop shouting". Pathophysiology of how phenomenon happens: - 8th nerve fibers are activated in an S-curve fashion. - At lower loudness only a small % of fibers are activated, and above approximately 95dB above SRT the peak of the slope is activated and a large % of fibers are activated - May be related to cochlear non-linearity from damage of the OHCs

Question 55

Define Dynamic Range of Hearing

Answer 55

The range (in dB) between SRT and UCL (Uncomfortable listening level) DR = UCL - SRT Normal dynamic range ~95-100dB

Question 56

How does dynamic range of hearing change with CHL vs. SNHL?

Answer 56

Recall: DR = UCL - SRT CHL: Both SRT and UCL shift equally by the same air-bone gap, therefore DR is the same SNHL: DR is smaller, because SRT is elevated but UCL stays around the same (Due to recruitment)

Question 57

How can you increase your dynamic range? 3

Answer 57

1. OHC modification 2. Recruitment (less recruitment??) 3. Stapedial reflex - helps with discrimination (decreases low frequency masking of high frequency sounds;; protective for loud, continuous sound -- which increases UCL) | Why recruitment? Wouldn't this make it the UCL "smaller"

Question 58

How to determine audiologically whether a lesion is cochlear in origin? ie. what are the tests of recruitment?

Answer 58

1. Dynamic range between SRT and Discomfort level with speech normally ~95dB. Decreasing DR = increasing recruitment 2. OAEs

Question 59

What are 7 causes of abnormally low SDS for a given PTA?

Answer 59

1. Retrocochlear Pathology 2. Auditory neuropathy (ANSD) 3. Central auditory processing disorder (CAPD) 4. Too low presentation level 5. Malingering 6. Neural type presbycusis 7. Language difficulty (ESL) Other causes of Low SDS in general: SNHL

Question 60

How can you tell if SDS is lower than what is expected for a given PTA?

Answer 60

Expect SDS + PTA ≥ 100. If less, consider retrocochlear pathology E.g. if PTA is 40dB, expect SDS ≥ 60% PTA and SRT should agree within 5dB

Question 61

What are 6 causes of CHL with intact reflexes?

Answer 61

1. Superior SCC dehiscence (3rd window) 2. Collapsing canals 3. Fracture of the stapedial arch 4. Lack of calibration 5. Malingering 6. Other third window phenomenon (e.g. enlarged vestibular aqueduct, x-linked gusher) ## Footnote C's - Crazy (malingering) - Crural fracture - Canal dehiscence - Calibration error - Collapsing canals

Question 62

What are otoacoustic emissions and how are they produced?

Answer 62

OAEs = sounds that are produced by the outer hair cells Pathophysiology: Caused by movement of the OHCs that tune the response of the tectorial membrane to sound - OHCs produce a secondary disruption of the tectorial membrane when the wave travels (and disrupts the membrane primarily) in order to amplify the signal to the brain - This secondary disruption generates a byproduct of lower amplitude wave that travels back on the membrane to the middle ear to canal and is recorded by a microphone

Question 63

What is Prestin? Where is it found?

Answer 63

Prestin = OHC protein that gives OHCs the ability to elongate and contract, which is critical to OHCs functions as part of the cochlear amplifier Cochlear amplifier: a positive feedback mechanism within the cochlea that increases the amplitude and frequency selectivity of sound vibration. Cochlea detects signal, sends it to brain, brain tells OHC to stiffen in particular areas to get certain frequencies tuned better. OAEs are thought to be a by-product of cochlear amplifier function

Question 64

What are the 4 types of OAEs? When are OAEs not detectable for each?

Answer 64

Generally, spontaneous vs. evoked (in response to external noise stimulus) 1. Spontaneous OAEs - Occur in 50% of normal ears without any external stimulus - Absent in SNHL >30dB - Usually narrow-band signals with 10-30dB SPL Evoked OAEs - not detectable in patients with hearing loss > 50-55dB; three subtypes: 2. Stimulus/Sustained frequency OAEs - Evoked by a continuous pure tone stimulus; produces a continuous tonal emission of same frequency 3. Transient evoked OAEs - Multifrequency response evoked by click given - Response ~5-10ms after sound stimulus (latency time for emission to travel back) - Contains multiple frequencies - Absent in SNHL > 50 dB (40dB depending where you read) - **Most sensitive measure of hearing loss in children! ** - Not effective for evaluating higher frequency hearing loss 4. Distortion potential OAEs (DPOAEs) - Used in newborn hearing screening - 2 pure tones separated by a few hundred Hz are presented simultaneously (Frequencies - F1 lower tone and F2 higher tone;; F2 = 1.2F1) and this results in a distorition product that is lower than either of the 2 stimulus frequencies - Largest response emission (sound produced from the OHC) should occur at the frequency calculated as **(2xF1) - F2** (this is the distortion product - DP). If the OHC produces this sound at 2F1-F2, this means that the OHC at F2 frequency are functioning normally, so normal hearing at F2 - Amplitude of DP - NF (noise floor) should be > 6dB - Absent in SNHL > 50dB - Advantage - response emission occurs at a frequency different from the two pure tone stimuli, which makes its measurement easily distinguishable - Sensitive test for cochlear function ## Footnote http://www.oae.it/old/definitions/DPOAE.html

Question 65

What is the anatomic pathway of an otoacoustic emission?

Answer 65

1. Outer hair cell 2. Basilar membrane 3. Cochlear fluids (Scala Tympani) 4. Oval window 5. Ossicles 6. Tympanic membrane

Question 66

What are the 6 indications for OAE testing?

Answer 66

1. Newborn hearing screening 2. Patients that are difficult to test 3. Rule out pseudohypoacusis (malingering) 4. Auditory neuropathy workup 5. Ototoxicity 6. Noise induced hearing loss

Question 67

What are 5 reasons that OAEs are absent?

Answer 67

1. Cochlear abnormality 2. Middle ear fluid or OM 3. External ear obstruction (FB, cerumen) 4. Negative middle ear pressure 5. TM perforation/tube (sometimes) *CHL often have absent OAE!

Question 68

What are 5 factors that influence success of OAEs for hearing screens?

Answer 68

1. Noise level in test environment 2. Vernix/debris in the EAC 3. EAC collapse 4. Middle ear fluid/mesenchyme/dysfunction 5. Decrease responses in low birth weight infants and premies

Question 69

What are cochlear microphonics? How are they measured? What are the clinical implications?

Answer 69

Definition: Alternating voltage current generated across the membranes on OHCs, which is induced by movement of the basilar membrane. Its measurement suggests the integrity of OHCs. Measure via scalp electrodes. Result: Appears as electrical activity prior to Wave 1 on ABR Clinical Implications: Abnormal ABR + present cochlear microphonics = suggest auditory neuropathy spectrum disorder

Question 70

Define Auditory Brainstem Reflex (ABR). How do you measure the reflex?

Answer 70

Definition: Measurement and graphing of sound evoked action potentials from the cochlear nerve to the brain. Measured via scalp electrodes. Electrode set up: 1. Vertex scalp electrode 2. Bilateral earlobes OR mastoids 3. Forehead/anywhere else (ground electrode) Slow clicks played at high volume intensity (80-90dB adult)

Question 71

What are 6 indications for an ABR?

Answer 71

1. Newborn hearing screening (e.g. high risk, failed OAEs) - screening, not complete for a diagnostic test (Automated ABR is a screening, says pass or refer; diagnostic ABR is manual where you look at the waves) 2. Threshold testing where behavioural testing cannot be easily done, or in pseudohypocusis 3. Intraoperative cochlear nerve monitoring 4. Diagnosis of retrocochlear lesions 5. Auditory neuropathy (present cochlear microphonics, absent or abnormal ABR) 6. DIagnosis of brainstem lesions or pathology

Question 72

How do you interpret an ABR waves? Which ones are observed at birth?

Answer 72

First 5 waves (wave I-V) on the abr are interpreted, which correspond to the ascending auditory pathway. ECOLI: Wave I, II: Eighth nerve (I is distal nerve, II is proximal nerve) Wave III: Cochlear nucleus (junction of pons and medulla) Wave IV: Superior olivary complex (rostral medulla to pons - first bilateral input; OHC/IHC input efferents originate here) Wave V: Lateral lamniscus of midbrain (largest wave) Wave VI, VII: Inferior colliculus of midbrain Waves beyond this: Medial geniculate ganglion (thalamus), auditory cortex (Brodman 41/42) Graph: Y axis - µV X axis - ms Only Wave I, III, and V are observed at birth. The latency between I and V is prolonged at birth as well.

Question 73

What are the absolute lantencies of each wave on the ABR? | ie. the time they show up on the graph

Answer 73

I - 2ms (1.5-2) II - 3ms (2.5-3) III - 4ms (3.5-4) IV - 5ms (4.5-5) V - 6ms (normal V interaural difference should be < 0.2ms) (5.5-6) *Just add 1 to wave number for absolute latency

Question 74

What are the normal interwave intervals differences on ABR?

Answer 74

- Wave I and III separated ~2ms. Normal interval < 2.3ms - Wave III and V separated by ~2ms. Normal interval < 2.1ms - Wave I and V separated by ~4ms. Normal interval < 4.4-4.6ms - Interaural wave V latency less than 0.2-0.4ms | Mnemonic: 2, 2, 4.4, 0.2

Question 75

Which wave on the ABR is most important?

Answer 75

Wave V is the most robust ABR measurement and persists even with significant hearing loss. An absent wave V in the presence of a replicated wave I or III is a definitive diagnostic indicator for a retrocochlear lesion

Question 76

What are considered abnormal latencies on an ABR?

Answer 76

I-III --> 2.3ms or higher III-V --> 2.1ms or higher I-V --> 4.4ms or higher Interaural latency difference to V --> 0.4ms or higher

Question 77

What is suggestive of a retrocochlear lesion on ABR? Name 3 potential ways

Answer 77

1. Absent wave V in the presence of a replicated wave I or III (diagnostic indicator) 2. I-III (more sensitive) or I-V latency 3. I-V latency is affected more by cochlear hearing impairment, so measurement of I-III is typically considered the gold standard for neurologic diagnostic applications

Question 78

What are the most sensitive latencies on ABR to suggest retrocochlear lesion?

Answer 78

I to III or I to V

Question 79

Describe the patterns of ABR for 4 CHL and 3 SNHL

Answer 79

CHL: All waves delayed (shifted to right), normal morphology, normal interwave distance, LOWER amplitude SNHL: Small wave I, long interwave latency/delayed waves, overall poor morphology ## Footnote Vancouver notes 231

Question 80

Describe ABR findings for Retrocochlear pathology

Answer 80

- Normal wave I but all others delayed - Altered morphology - Sometimes, no waves at all - Wave V latency prolonged (interaural latency >0.2ms, intra-aural latency >5.7ms) - Interpeak intervals (I-III, I-V, III-V) prolonged and delayed - Interaural intervals also prolonged

Question 81

What is the auditory steady state response? How is it measured, what are its indications, and what are the advantages and disadvantages?

Answer 81

Definition: Alternative to ABR, it is a measurement and graphing of frequency specific sound evoked action potentials from cochlear nerve to brain. It is used to estimate hearing sensitivity in individuals with various degrees and configurations of sensorineural hearing loss Indications (same as ABR) 1. Newborn hearing screening (e.g. high risk, failed OAEs) 2. Threshold testing where behavioural testing cannot be easily done, or in pseudohypocusis 3. Intraoperative cochlear nerve monitoring 4. Diagnosis of retrocochlear lesions 5. Auditory neuropathy (present cochlear microphonics, absent or abnormal ABR) 6. DIagnosis of brainstem lesions or pathology Technique: - Measured via scalp electrodes - Rapid series of tone bursts (vs. slow clicks ABR) across 500-4000Hz and various amplitudes - Measures response to different sound frequencies (vs. ABR which looks at response latencies) Advantage: - Faster to administer - Can do both ears simultaneously and multiple frequencies together - More sensitive (can differentiate between severe and profound HL) - Good correlation to behavioural thresholds Disadvantage: - Too sensitive, artifacts common - Unsure of applicability to bone conduction

Question 82

Describe 4 similarities and 6 differences between ABR and ASSR

Answer 82

Similarities: - Both deliver auditory stimulus - Both stimulate the auditory system - Both record bioelectric responses from the auditory system via electrodes - The patient does not have to respond volitionally Differences: - Stimulus: ABR Click or Broadband tone burst; ASSR amplitude or frequency modulated sound (pure tones) - Duration of stimulus: ABR slower rate; ASSR presented rapidly - Timing of stimulus: ABR One frequency and one ear at a time; ASSR 4 frequencies at the same time, both ears at the same time - Unit of measurement: ABR Microvolts; ASSR Nanovolts - Analysis: ABR subjective analysis of amplitude and latency; ASSR statistical analysis of the probability of a response, usually at a 95% confidence level - Results: ASSR estimates hearing sensitivity at a specific frequency with >80dB, but ABR cannot

Question 83

What are 6 factors that can affect ABR test results?

Answer 83

1. Body temperature 2. Age < 18 months (only wave I, III, V observed at birth, and latency between I and V is prolonged at birth) 3. Gender 4. Hearing loss > 50 dB (correction 0.1ms/10dB) 5. Stimulus intensity - important: may affect amplitude, but not latency 6. Medications - Diazepam (benzos), Phenytoin, Lidocaine

Question 84

What are common electrophysiologial tests of hearing? 4

Answer 84

1. Otoacoustic Emissions (OAEs) - Spontaneous - Evoked --> Transient (TEOAE) --> Distortion Product (DPOAE) --> Stimulus Frequency 2. Electrocochleography (ECoG) 3. Auditory Evoked Potentials - Auditory brainstem response (ABR) - Auditory Steady State Response (ASSR) - Cortical Evoked Potentials

Question 85

Where are Wernicke's area, Broca's area and the Auditory Cortex? What are their implications with auditory and speech function?

Answer 85

Wernicke's Area: Brodman area 22 - superior temporal bone - Comprehension of written and spoken language Broca's Area: Brodman area 44, 45 - frontal lobe of the dominant hemisphere - speech production Auditory cortex - Brodman area 41, 42 - Superior temporal lobe ## Footnote Vancouver notes Page 230

Question 86

What are the limits of ABR testing thresholds?

Answer 86

Air Conduction: 500, 1000, 2000, 4000 Hz Bone Conduction: 500 and 2000 Hz only

Question 87

Describe ABR findings that may be seen in Multiple Sclerosis?

Answer 87

Interpeak intervals longer, with normal hearing

Question 88

What are 3 hints on clinical history that suggests pseudo-hypoacusis (malingering?)

Answer 88

1. History inconsistent with that of hearing loss recorded on testing 2. Referral source is for a compensation case, may name the speciic incident that caused the loss 3. Behaviours suspicious for invalid responding during testing

Question 89

What are 10 audiological findings suggestive of pseudo-hypoacusis (malingering)?

Answer 89

1. Bone conduction thresholds are worse than air conduction thresholds 2. Poor Test-retest reliability of pure tone thresholds (should be within 5dB) 3. Disagreement between SRT and PTA (should be normally within 5-7dB) 4. Good SDS at or near SRT (normally SDS is ~30-50dB above SRT) 5. Non-response by patient in unmasked air conduction stimuli with suspected unilateral hearing loss, indicating an absence of crossover hearing (shadow curve, occurs at 0dB BC, 40dB AC) 6. Normal stapedial reflexes; Presence of acoustic reflexes with audiometric air bone gaps or AC < reflex thresholds 7. Normal ABR 8. Positive normal OAEs 9. Repeat only parts of words during speech testing 10. Failure of special tests for malingering

Question 90

What are 9 special tests for pseudohypoacusis (malingering)? Which are more useful for adults vs. children?

Answer 90

ADULTS: 1. Stenger Test - Test for unilateral/asymmetric HL > 25dB - Based on the Stenger effect (bilateral fusion principle) that when 2 tones of same frequency are presented simultaneously to both ears, only the louder tone is perceived; or at same volume, the tone is heard in the better hearing ear (which is perceived as louder). - How it works: Play the louder tone in the bad ear (but still below their "threshold of the bad ear"), and above their threshold in the good ear (but make sure this is overall quieter than the bad ear; ie. loudest noise is in the bad ear). True HL -- pt will hear tone in the good ear only and accurately perceive sound. PseudoHL -- pt will only hear tone in their "bad" ear (because this is the loudest tone based on fusion principle) and will claim to hear nothing. 2. Lombard test - Based on the phenomenon that one involuntarily tends to increase the volume of their voice in the presence of background noise, and that noise interferes with self-monitoring - Reliability and accuracy overall poor - Patient asked to read from a book or have a conversation. As they read or talk, background noise is induced and amplified, but still below patient's claimed "threshold". - True HL = pts voice volume doesn't change as they can't hear the masking noise (that is below their threshold) - Pseudo HL = pts voice level rises as masking increases 3. Lee's Speech delayed auditory feedback: - Based on the principle that repeating the same dialogue as you are hearing makes you stutter (inability to process both incoming and outgoing signals simultaneously) - Patient is asked to read aloud a passage and this is recorded in the sound booth. - Have patient re-read the passage and play back their recording at a slight delayed, below their "thresholds" - True HL - Patient reads passage smoothly as they don't hear the dialogue below their threshold - Pseudo HL - Patient starts stuttering during attempt to read 4. Chimani Moos Test (Modified Weber Test) - Based on premise that sound will localize to the occluded ear via bone conduction - Method: Perform Weber test, and patient will indicate hearing in their "good" ear. Then perform Weber again while finger occluding their "good" ear. - True HL -- sound perception IMPROVES in good ear once occluded - Pseudo HL -- Patient will say they cannot hear the sound at all, because they think "now my good ear is blocked" 5. Lip Reading Test - If they do poorly but say they rely on lip reading to help hear, highly suspicious for malingering CHILDREN: 6. Yes/No test - Based on premise that children don't know enough to lie by omission - Method: If you hear a tone say yes, if you don't say no - True HL -- Child will say yes if they hear the sound and will say nothing if they don't - Pseudo HL -- Child will say "no" immediately after sounds (within a time-locked period) -- can also be used in adults - In adults, some patients will say no to levels presented above the level they tested as their "threshold" 7. Pulse Count Test - Method: Present a child with rapid pulse tones above and below hearing 'threshold' and ask them to count the number of tones heard - True HL -- accurately report the number of pulses above threshold - Pseudo HL -- difficulty accurately counting the number of tones (if they are trying to fake), or will count all the tones) ALL: 8. OAEs - presence indicates that hearing loss can be no worse than 40dB HL 9. ABR - Objective test Always check your hardware and re-educate the patient!

Question 91

What tuning fork should you use for Weber/Rinne?

Answer 91

512Hz

Question 92

Negative Rinne Test (AC worse than BC) - what is the degree of CHL?

Answer 92

Depends on the Tuning fork used: First value is KJLee source, second is Cummings 1. 256 Hz >15dB or more; 20-30 dB 2. 512 Hz >25 dB loss; 30-45 dB 3. 1024 Hz >35dB loss; 45-60 dB

Question 93

What is Electrocochleography (ECoG)? How is it measured? What structures does ECoG provide information on?

Answer 93

Definition: Measures electrical potentials generated by the cochlea and cochlear nerve (beginning of auditory pathway) in response to a sound stimulus. (vs. ABR which records entire auditory pathway) Measured via electrodes placed in the EAC, at the TM, or at the promontory. Ground electrode on forehead, and reference electrode on mastoid. - Wide band click most commonly used stimulus, electrical response is measured for 10ms. - Can test hearing thresholds between 3-4kHz Assess hair cells, dendritic and axonal components (ie. includes both the cochlear microphonics and nerve action potentials together).

Question 94

What are 4 measurable potentials in electrocochleography, their source, and their clinical utility?

Answer 94

Depending on the mode of stimulus, the ECoG response may consist of cochlear microphonics, the summating potential, and the whole nerve action potential generated by the eighth nerve. Resting Potential: - **Endocochlear Potential**: Resting potential of +80mV of the scala media, maintained by the stria vascularis Na-K pump. Direct current response Stimulated potentials: - **Cochlear Microphonics**: The cochlear microphonic (CM) is an alternating current (AC) voltage that mirrors the waveform of the acoustic stimulus. It is dominated by the OHCs of the organ of corti. Proportional to basilar membrane displacement. K+ ion inflows in OHC, altered by motion of the basilar membrane from sound. Present in ANSD - **Summating Potential**: The directional current (DC) response of the hair cells as they move in conjunction with the basilar membrane. This DC is due to asymmetric movement of the basilar membrane - **Compound Action potential**: All or none discharge of the auditory nerve CMs are alternating current potentials which originate from the hair cells, especially OHCs. SP is a direct current response generated by the hair cells of the organ of corti and a reflection of the displacement –time pattern of the cochlear partition. AP is the summed response of numerous, at times thousands, of ANFs firing synchronously. That is why it is called Compound AP.

Question 95

What are the potentials of the IHC and OHC?

Answer 95

IHC Potential: ~35mV OHC Potential: ~70mV

Question 96

What are the auditory nerve spontaneous discharge rates?

Answer 96

High spontaneous fibers = >18/sec (up to 120/sec) Medium = 0.5-18/sec Low < 0.5/sec High firing fibers have lower thresholds, and low firing fibers have higher thresholds

Question 97

What situations would you see an increased SP/AP ratio?

Answer 97

Endolymphatic hydrops, SP/AP > 0.45-5 - 2/3 of Meniere's patients will have increased ratio - Also seen in syphillis

Question 98

What is considered an abnormal SP/AP ratio, depending on where you put the electrode?

Answer 98

EAC > 50% TM > 40% Transtympanic > 30% ## Footnote Less when closer Vancouver page 232

Question 99

What are 7 indications for Electrocochleography (ECoG)?

Answer 99

1. Meniere's Disease: - Hydrops increases elasticity of basilar membrane --> increased SP. This increases SP/AP ratio. Abnormal > 0.5 2. SCCD: - Third window effect changes impedence at the scala vestibuli side of the basilar membrane compared to tympani side. This results in a basilar membrane bias which increases the SP. Abnormal > 0.4 3. Threshold Testing 4. Auditory neuropathy 5. Vestibular schwannoma 5. Intraoperative nerve integrity monitoring (near-field technique) 6. Audiometric evaluation prior to aural atresia repair if EAC is patent

Question 100

What does absent/reduced ECoG AP indicate?

Answer 100

Cochlear ischemia (e.g. secondary to injury to the labyrinthine artery)

Question 101

Describe 3 different audiometric testing methods for children 0-5 years of age? When is their optimum test age?

Answer 101

1. Behavioural Observed Audiometry - 0-6 months - Unconditioned responses to noise (warble tones, narrow band of tones via speaker) - observe infants responses to sound stimuli (eye widening, startle, head turn) - Infants habituate rapidly - Imprecise, gross estimate of infant auditory thresholds - Only tests the better ear 2. Visually reinforced audiometry (VRA) - 6 months to 2 years - Response to sound is rewarded by a visual stimulus - Operant conditioning (like Pavlov's dogs) - Behavioural diagnostic method of choice in children in this age group 3. Conditioned play audiometry - 2-5 years old - Child performs a task in response to auditory stimulus (e.g. every time you hear a noise, drop the toy in the bucket) - Task changes to keep child's interest

Question 102

Case: Weber lateralizes to the right, Rinne right shows AC > BC. Rinne on left shows BC > AC. What 2 audiological situations could give these results?

Answer 102

1. Right normal hearing, Left mixed hearing loss 2. Right normal hearing, left dead ear (BC > AC on left because transmitted to the right side)

Question 103

What degree of hearing loss can different tuning forks detect on the Rinne test?

Answer 103

256 Hz tuning fork: 15-30 dB difference 512 Hz tuning fork: 30-45 dB difference 1024 Hz tuning fork: 45-60 dB difference Normal hearing ears can differentiate 5dB between sides on a Weber

Question 104

What tuning fork is usually used for tuning fork tests?

Answer 104

512 Hz tuning fork

Question 105

Describe how to perform and interpret a Weber, Rinne, Gelle, and Bing Tuning fork tests

Answer 105

Weber: 512 Hz tuning fork over midline forehead, and ask patient which side it lateralizes to. This will either represent ipsilateral CHL or contralateral SNHL. Rinne: 512 Hz tuning fork placed over mastoid process, once no longer audible, then ask if they can still hear it over ear. AC > BC normal; BC > AC suggests CHL. Positive Rinne actually means "normal". Gelle: 512 Hz tuning fork on mastoid, examiner then induces EAC pressure (either with Spiegel speculum or tragal pressure) - Decrease in sound = normal of SNHL - No change in sound level = ossicular discontinuity or fixation - Mechanism of action: Inward ossicular pressure causes increased intralabyrinthine pressure which causes decreased basilar membrane movement. You lose this with ossicular discontinuity or pressure (no pressure to decrease the basilar membrane movement, therefore no change in sound) Bing: 512 Hz tuning fork on mastoid. Once patient reports sound is no longer audible, occlude the EAC. - Increase in sound = normal or SNHL - No change in sound level = CHL - MOA: Occluding EAC causes a CHL which should increase the bone conduction sound level

Question 106

What are 8 audiologic findings suggestive of a retrocochlear lesion?

Answer 106

1. Asymmetric SNHL on pure tone testing (>15dB in 2 frequencies except 6K & 8K, or >30dB in 1 frequency) 2. SDS asymmetry of 12-20% or unusually poor compared to PTA 3. PiPb rollover > 40% - paradoxical decrease in speech discrimination with increase in intensity 4. Absent stapedial reflex (with CN VIII loss > 40dB) 5. Positive reflex decay test 6. Abnormal and delayed wave V on ABR (e.g. prolonged I-III or I-V latency) 7. Interaural wave V latency difference > 0.4ms 8. Auditory fatigue (change of auditory threshold with continuous acoustic stimulus)