HESP411 exam 2

What are electroacoustic procedures?

audiologic tests that involve the measurement of sounds within the external ear canal

Types of electroacoustic procedures

* tympanometry
* acoustic reflex
* otoacoustic emissions

clinical uses of electroacoustic procedures

* objective test permitting assessment of auditory function in patients who cannot participate in behavioral testing
* useful in infants and young children
* hearing screening of newborn babies
* highly sensitive to dysfunction

____ + ____ = acoustic immittance

IMpedance → opposition to flow of energy through the ME system from ear drum to inner ear, stiffness

AdMITTANCE → ease that energy flows through middle ear, aka compliance

Acoustic immittance procedure: Tympanometry

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* “a way of measuring how acoustic immittance of the middle ear system changes as air pressure is varied in the external ear canal”

Clinical value of tympanometry

* allows audiologists to objectively describe and quantify how well the middle ear is working
* highly sensitive: results are distinctly different for patients with disorders that increase stiffness in ME than for patient with excessive flexibility in ossicular chain
* most commonly recorded acoustic immitance test

Why is tympanometry the most commonly recorded acoustic immittance test?

* its quick
* essential for detection of ME dysfunction
* results yield graph called tympanogram

Why do you want to vary pressure in tympanometry?

TM works best when pressure inside ME space is equal to pressure at TM

Tympanometry test equipment and what they do

* loudspeaker: produces pure tones
* microphone: records sound returned from TM (essentially what we analyze)
* manometer: changes air pressure from -400 to +200
* probe tip dependent on patient

What is a hermetic seal

air tight seal by probe in tympanometry

What is a tympanogram?

* Plot showing admittance of the ME system as air pressure is varied within the ear canal (mL or mmhos)
* Air pressure is increased to +200 daPa and then decreased to -300 daPa

Pressure with greatest admittance is when pressure is _____ in ME and external ear canal

matched

Components of tympanogram: ear canal volume

* Estimated for the space enclosed between probe tip and tympanic membrane 


* Measured in mL or cm^3
* If fall outside of range, may be some pathology

ear canal volume normative data (children and adult)

* children → mean: 0.7, 90% range: 0.4-1.0
* adult → mean: 1.1, 90% range: 0.6-1.5

Possible pathologies with abnormally large ECV

* TM perforation
* PE tube
* if large, assume something wrong with TM

Possible pathologies with abnormally small ECV

* cerumen
* blocked probe
* probe against canal wall
* assume something taking up space in ear

Components of tympanogram: Static acoustic admittance/compliance

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* Value measured at maximum compliance around 0 daPa in normal ME system (peak admittance)
* Pressure equal on both sides of TM
* Measured in mL or mmhos (sometimes Ytm)

peak admittance normative data (children and adult)

* children → mean: 0.5, 90% range: 0.2-0.9
* adults → mean: 0.8, 90% range: 0.3-1.4

Classifications of static acoustic admittance/compliance

* high/deep (hyperflaccid)
* more sound than normal admitted
* normal
* within normal range
* low/shallow (stiff)
* less sound than normal admitted

Components of tympanogram: Peak pressure

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* Measured in daPa
* Often abbreviated TPP
* Point of maximum compliance 
* Peak when the external canal pressure (that’s being varied) is equal to the pressure behind the ear drum (ME space)

Peak pressure normative data (children and adults)

children/adults: -100 to +50

Classifications of peak pressure

* normal: Ear works best when pressures in external ear canal and ME match
* negative: Peak admittance would be in negatives
* negative pressure in ME which absorbs sound 

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Type A tympanogram

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* Normal 
* Maximum peak compliance between 0.30-1.50 mL
* Peak pressure falls within +50 to -100 daPa
* Consider ear canal volume 
* No pathology

Type As

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* “S” is for shallow or stiffness 
* Abnormal 
* Maximum peak compliance is less than 0.30 mL
* Admittance is shallow 
* Peak pressure falls within +50 to -100 daPa
* Within normal range 
* Consider ear canal volume 

Type Ad

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* “D” is for deep (hypercompliant or hyperflaccid)
* Abnormal 
* Maximum peak compliance is more than 1.50 mL
* Increased admittance
* Peak pressure falls within +50 to -100 daPa
* Within normal range
* Consider ear canal volume

Type B

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* Abnormal 
* No peak 
* Absolutely consider ear canal volume 
* If ear drum not intact, large ECV would be expected but still type B
* If ear drum is normal, normal ECV would mean a problem in ME

Type C

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* Abnormal 
* Maximum peak compliance between 0.3-1.50 mL
* Within normal range
* Peak pressure falls greater than -100 daPa
* Negative pressure, so falls outside of normal range
* Consider ear canal volume

Conventional low frequency probe tone 

226 Hz: quite effective for detecting stiffness related middle ear dysfunction

Infants less than 6 months of age probe tone

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* 1000Hz probe tone 
* The characteristics of baby ears are different 
* Floppy ear canals may move, so increase frequency to work better with infant ear development 

Jerger tympanometry “Types” (each classification)

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* Type A: normal compliance, normal pressure 
* Type As: shallow compliance, normal pressure 
* Type Ad: increased compliance, normal pressure
* Type B
* With normal ECV: no peak compliance (and therefore no peak pressure)
* With small ECV: blocked external ear canal; probe against canal wall; blocked PE tube 
* With ECV: TM perf; PE tube in place and patent 
* Type C: normal compliance, negative pressure
* Type Cs: shallow compliance, negative pressure 

Type A possible pathologies

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* Normal middle ear function 
* Possible pathology 
* Normal hearing 
* Sensorineural hearing loss 

Type As possible pathologies

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* Think about patient complaints on case history and other test results
* Resolving ear infection 
* Beginning ear infection 
* Tympanisclerosis 
* Otosclerosis
* Could be conductive or mixed, abnormal otoscopy

Type Ad possible pathologies

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* Normal pressure, increased compliance 
* Possible pathology 
* Think about patient complaints on case history and other test results 
* Scar tissue on TM 
* Ossicular chain discontinuity 
* Normal otoscopy

Type B possible pathologies (normal ECV)

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* Think about patient complaints on case history and other test results 
* **Otitis media with effusion** 
* Effusion 
* Surgical ear 
* PE tube in place and clogged
* Conductive or mixed HL
* Abnormal otoscopy

Type B possible pathologies (large ECV)

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* Think about patient complaints on case history and other test results 
* TM perforation 
* PE tube in place and patent 

Type B possible pathologies (small ECV)

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* Think about patient complaints on case history and other test results 
* Probe blocked 
* Probe against canal wall 
* Cerumen in ear canal 
* Foreign object in ear canal 
* Conductive HL

Type C possible pathologies

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* Negative pressure, normal compliance 
* Eustachian tube **not** functioning properly 
* When ears feel full and need to pop
* Think about patient complaints on case history and other test results 
* Beginning ear infection 
* Resolving ear infection 
* Allergies 
* Did the person recently fly?

definition of acoustic reflex

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sonomotor response consisting of a contraction of the ME muscles upon high intensity sound stimulation

what muscles are part of acoustic reflex and what CN innervates them?

* Tensor tympani muscle is connected to the malleus and innervated by CN V (trigeminal)
* Stapedius muscle is connected to the neck of the stapes and innervated by CN VII (facial)

what is being measured in acoustic reflex?

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* Stapedius muscle contracts in response to high intensity stimuli exceeding about 70 dB HL
* Contraction of muscles stiffens the ME system and decreases admittance of **both** ME systems

presence of acoustic reflexes is highly dependent on status of _______ and ____

middle and outer ear → pathologies obscure reflex results

acoustic reflex equipment

* same as tympanometry
* measured at peak admittance
* simulus pure tones: 500-4000Hz

measurement pathways: ipsilateral

* uncrossed
* Sound stimulus is presented to one ear and the change in the ME compliance is recorded in the same ear (stimulus ear and probe ear are the same)

measurement pathways: contralateral

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* crossed
* Sound stimulus is presented to one ear (stimulus ear) and the change in ME compliance is recorded in the opposite ear (probe ear)

when sound is presented to one ear, the stapedius muscles in ____ contract

both ears → bilateral reflex

If stimulus is observed, what do we search for?

Acoustic reflex threshold

What is Acoustic reflex threshold?

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* “The lowest intensity at which a middle ear immittance change can be detected in response to sound”
* Magnitude of immitance change increases as the stimulus levels increases above acoustic reflex threshold 

What do we do if the reflex is not observed?

increase intensity of stimulus

what should be referenced to elicit the reflex?

level of stimuli

afferent structures of acoustic reflex pathway

* cochlea
* portion of CN VIII

_____ contributes to the acoustic reflex arc in both the ipsilateral and contralateral conditions 

cochlear nucleus

Additional neurons in ________ and ____ contribute to the acoustic reflex pathways in the *contralateral* measurement condition 

trapezoid body and superior olivary complex

efferent structures of acoustic reflex pathway

CN VII (facial nerve)

ART with ME pathology

* may not be able to measure bc stapedius muscle is within ear

ART with sensory hearing loss

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* Reflexes may still be normal with a moderate degree (50 dB HL) of __sensory (cochlear)__ hearing loss
* For patients with greater degrees of HL, you’ll need higher level stimulation to elicit reflex if you are even able to (“elevated” or “absent”)

damage to cochlea 50db HL or lower (unilat)

Unaffected ipsi: normal

Affected ipsi: normal

Unaffected contra: normal

Affected contra: normal

damage to cochlea over 50dB HL (unilat)

Unaffected ipsi: normal

Affected ipsi: abnormal (A/**E**)

Unaffected contra: normal

Affected contra: abnormal (A/**E**)

damage to CN VIII (unilat)

Unaffected ipsi: normal

Affected ipsi: abnormal (**A**/E)

Unaffected contra: normal

Affected contra: abnormal (**A**/E)

retrocochlear (brainstem) disorder (unilat)

Unaffected ipsi: normal

Affected ipsi: normal

Unaffected contra: abnormal (**A**/E)

Affected contra: abnormal (**A**/E)

damage to VII nerve (unilat)

Unaffected ipsi: normal

Affected ipsi: abnormal (A)

Unaffected contra: abnormal (**A**)

Affected contra: normal

damage to ME (unilat)

Unaffected ipsi: normal

Affected ipsi: ABSENT

Unaffected contra: abnormal (**A**/E)

Affected contra: ABSENT

small intra-axial brainstem damage

both ipsi present, both contra absent

large intra-axial brainstem damage

all reflexes absent

Acoustic reflex interpretation: CHL

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* While muscle contraction may be present in conductive hearing loss it may not be observed in the presence of an already stiffened TM or ME mechanism (probe effect/double whammy)

Acoustic reflex interpretation: mild-mod SHL

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* Mild to moderate cochlear HL (50 dB HL or softer) expected at lower sensation levels (< 70 dB SL) but normal intensity level 

Acoustic reflex interpretation: severe SHL

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* Severe cochlear HL (60 dB HL or greater) reflex is expected to be absent (it might be elevated and that might not be entirely unexpected)
* Mod severe +, expect absent 
* May take increased level of sound to stimulate auditory reflex, would be sign of recruitment

Acoustic reflex interpretation: retrocochlear HL

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* Retrocohlear HL is most likely to have an absent reflex (sometimes you might see elevated, but rarely)
* Any time beyond cochlea, reflex almost always absent 
* Cant relay information ot elicit response

definition of acoustic reflex decay

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*  a gradual relaxation of muscle contraction in the presence of a continuing sound (10 seconds) that elicits a reflex 
* A reflex at 500 and 1000 Hz elicited at 10 dB above the acoustic reflex threshold will maintain contraction for 10 seconds for normal ears and those with cochlear HL

what HL is acoustic reflex decay observed?

retrocochlear → defined as a 50% decrease in the original magnitude of the contraction within a 10 second period

what are the 3 major ABR waves?

I, III, V

anatomical generators of major ABR waves

Wave I: auditory nerve

Wave III: pons

Wave V: midbrain

the most prominent ABR wave

V

first 5 peaks happen within ___ ms

first 10 ms

definition of latency

time interval from presentation of the stimulus to the occurrence of a wave (ms)

absolute latency definition/ values expected of waves

* how long after stim onset each wave occurs
* Wave I: 1.5 ms
* Wave III: 3.7 ms
* Wave V: 5.7ms

interpeak latency definition/ values expected of waves

* how long between each wave
* Wave I-III: 2.2 ms
* Wave III-V: 2.0 ms


* Wave I-V: 4.2ms

interaural latency definition

* compare between ears
* bilat vs unilat

Definition of amplitude/values expected of waves

size of the wave from its peak to the valley (microvolts)

Wave I: 0.2 microvolts

Wave V: 0.5 microvolts

what are the three major changes in waveform as stimulus intensity level is decreased?

* Latency of the waves increases
* Amplitude of the waves decreases
* Only wave V remains at the lowest intensity level at which an ABR is still present

where is a patients ABR threshold?

corresponds to intensity level where ABR wave V is last seen 

how do you calculate auditory threshold on an audiogram from ABR threshold?

Subtract 10 dB from ABR threshold to estimate patient’s auditory threshold to plot on an audiogram

Latency-Intensity Function (wave 5) for CHL

sound takes longer to get through pathology, so intensities louder and latencies longer on graph

Latency-Intensity Function (wave 5) for SHL

elevated intensity thresholds, lower intensities have longer latency and return more normal at high intensities

Latency-Intensity Function (wave 5) for retrocochlear pathologies

* Effects of tumors
* delays in wave latencies
* I-III delays
* I-V delays
* can detect acoustic tumor
* interaural latencies
* between ear time (absolute latency longer on affected side)
* absent/missing waves
* can sometimes detect tumors in pons

what is intraoperative monitoring?

* during surgery, audiologists sometimes called on to make sure they don’t cut though auditory nerve or other brainstem areas
* also can monitor facial nerve

what is an electrocochleography (ECochG) used for?

to diagnose Menier’s disease

other AERs

*  Auditory Steady State Response (ASSR)
* Cortical Auditory Evoked Responses

What is the Joint Committee on Infant Hearing (JICH)?

* reported specified risk factors associated with hearing loss to identify infants at risk for permanent hearing loss
* recommended universal newborn hearing screening (UNHS) due to risk factor limitations


* guidelines endorse two techniques for screening
* UNBHS and EI is put in place in all states in the USA

what 3 objective measures are used to assess hearing in infants from birth to 6 months and when?

1. ABR—at birth
2. Otoacoustic emissions—at birth
3. Acoustic immittance—in follow-up

what does JCIH recommend for infants in NICU?

ABR test

goals of Early Hearing Detection & Intervention (EHDI)?

* hearing screening before 1 month of age for all infants
* audiological diagnosis before 3 months of age for children who do not pass screening
* early intervention services before 6 months of age for children diagnosed with HL

what is the crosscheck principle?

* critically important in prompt and accurate diagnosis of hearing loss in children
* careful selection and application of objective auditory tests within a test battery leads to accurate diagnosis
* hearing assessment with a collection of objective and then behavioral (subjective) when appropriate defines standard of care in pediatric audiology

diagnosis of Auditory Neuropathy Spectrum Disorder (ANSD)

* Present OAEs
* No detectable ABR waveform
* Acoustic reflexes absent


* Very poor WRS in quiet
* Even worse WRS in noise
* Hearing thresholds vary from one patient to the next

ANSD risk factors

* NICU stay
* Health problems before or during birth
* Acquired due to age related hearing loss
* Very poor word recognition performance
* Genetic link

Reason for hearing screening of preschool children

* to detect hearing loss that develops after birth, including hearing loss related to ear infections
* Hearing screenings are performed some time during preschool years and every year or two years after a child begins school

childhood hearing screening procedures

* Otoscopy
* Pure-tone audiometry (CPA or conventional audiometry)
* Otoacoustic emissions (OAEs) can offer an alternative to pure-tone screening
* Tympanometry
* Middle ear disorders are often encountered in pre-school children

what is the Individuals with Disabilities Education Act (IDEA)

* law that ensures appropriate education for all individuals with disabilities
* led to development of educational audiology

what do educational audiologists do?

* work in the school system to deliver a full spectrum of hearing services to all children and act as a liaison
* goal is to reduce the possible negative effects of the loss and/or disorder and to maximize the children's auditory learning and communication skills in the appropriate school environment

What are some of the challenges when doing hearing screenings on infants? In schools?

define otoacoustic emissions (OAEs)