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AUDIOLOGY. Danielle Billing. Outer Ear The part of the ear that is visible, often called the Pinna, and the ear canal, also called the External Auditory Meatus. Inner Ear The cochlea. The Hearing Mechanism. Middle Ear Consists of the tympanic membrane (eardrum) and the ossicles (bones).

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Audiology l.jpg

AUDIOLOGY

Danielle Billing


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Outer Ear

The part of the ear that is visible, often called the Pinna, and the ear canal, also called the External Auditory Meatus

Inner Ear

The cochlea

The Hearing Mechanism

Middle Ear

Consists of the tympanic membrane (eardrum) and the ossicles (bones)

Auditory Nerve

The nerve responsible for sending/ receiving auditory information

Peripheral Mechanism


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The Hearing Mechanism

The Brain

Responsible for processing and interpreting auditory information

Central Mechanism


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Outer Ear

Inner Ear

The Hearing Mechanism

Middle Ear

Auditory Nerve



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Outer Ear

Acoustic Energy

Inner Ear

Hydraulic Energy

The Hearing Mechanism

Middle Ear

Mechanical Energy

Auditory Nerve

Electrical Energy


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Outer Ear

Otitis Externa

Microtia

Anotia

Inner Ear

Meningitis

Noise damage

Heredity

Common Causes of Hearing Loss

Middle Ear

Otitis Media

Allergies

Cholesteotoma

Eustachian tube disfunction

Mastoiditis

Otosclerosis

Auditory Nerve

Auditory Neuropathy

Peripheral Mechanism

Conductive Loss

Central Mechanism

Sensorineural Loss

Mixed Loss


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Conductive Loss

A hearing loss caused by an obstruction or dysfunction of the outer or middle ear

Sensorineural Loss

A hearing loss caused by a dysfunction in the inner ear (sensori), or the central processing system (neural)

Types of Hearing Loss

  • Mixed Loss

    • A hearing loss caused by a combination of Conductive and Sensorineural Losses


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Degrees of Hearing Loss

  • Normal 10 or better

  • Minimal 11-25 d

  • Mild 26-40

  • Moderate 41-55

  • Moderately severe 56-70

  • Severe 71-90

  • Profound greater than 90


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Behavioral testing

Requires the patient to respond to a stimulus


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Introduction to Audiograms: What is an audiogram?

  • An audiogram is a graphical representation of the hearing thresholds of an individual

  • These thresholds are determined by the individual’s response to tones presented via earphones or ear inserts (air conduction), or a bone oscillator (bone conduction)


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Introduction to Audiograms: the Decibel

  • Decibel levels of common sounds

    • 0 dB- The softest sound a person can hear with normal hearing

    • 10 dB- normal breathing

    • 20 dB- whispering at 5 feet

    • 30 dB- soft whisper

    • 50 dB- rainfall

    • 60 dB- normal conversation

    • 110 dB- shouting in ear

    • 120 dB- thunder



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Speech testing

  • Two basic types:

    • Speech threshold tests

    • Speech recognition (supra-threshold) tests


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Speech Threshold Testing

  • Lowest level at which speech can be recognized or detected

    • SRT- speech recognition threshold

    • ST- spondee threshold

      • A spondee is a two-syllable word with each syllable receiving equal emphasis

  • The patient must correctly identify the speech material presented, typically by repeating the word

  • The SRT and pure tone average should be within +/- 10 dB of each other


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Supra-threshold Speech Testing:Speech Recognition Ability (SRA)

  • Ability to correctly recognize speech at supra-threshold levels (reported in percentage of correct responses at the intensity level of presentation)

    • 100% at 70 dB HL

    • 92% at 50 dB SL


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Electroacoustic and Electrophysiological testing

Does not require the patient to respond; responses are unconscious and automatic


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Ear Canal Volume (ECV)

  • Provides measure of volume of external ear canal

  • Volumes greater than 2.5 suggest:

    • Perforation or

    • Patent PE tube


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Tympanometry

  • Purpose: to test the function of the tympanic membrane and middle ear

  • Method: air is added and subtracted from the EAM while a tone is presented

  • Results presented on a graph called a tympanogram


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Tympanometry: Interpreting results

  • The shape of the tympanogram indicates the functionality of the middle ear


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Tympanometry: Interpreting results

Type A

Type Ad

Type As

Flaccid tympanic membrane

Ossicular disarticulation

(broken ossicular chain)

Normal Middle Ear

Stiff tympanic membrane

Otosclerosis

Tympanosclerosis


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Tympanometry: Interpreting results

Type B (low)

Type B (high)

Type C

Non-patent PE tubes

Patent PE tubes

Negative middle ear pressure


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Static Immitance

  • Definition: the height of the tympanogram at its peak

  • Helpful in diagnosing middle ear dysfunction

  • Able to detect small perforations in the tympanic membrane


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Static Immittance: Interpreting results

Flaccid: disarticulation, flaccid TM, etc.

2.5

Normal

.25

Stiff: otosclerosis tympanosclerosis, etc.


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Acoustic Reflex Threshold (ART)

  • “When a sound is of sufficient intensity, it will elicit a reflex of the middle ear musculature” (Stach, 1998, p.270)

  • The ART measures the threshold a which this reflex of the stapedius muscle occurs

  • Two types of reflex

    • Ipsilateral-reflex of the muscle of the stimulated ear- “uncrossed”

    • Contralateral-reflex of the muscle of the non-stimulated ear- “crossed”


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Acoustic Reflex Threshold (ART): Interpreting results

  • Individuals with normal hearing will have an ART between 70 and 100 dB HL

  • An elevated or absent response indicates a pathology of the hearing mechanism


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Acoustic Reflex Threshold (ART): Interpreting results

  • An absent contralateral reflex could indicate (when stimulus is presented to the right ear):

    • Right middle ear disorder

    • Right severe sensorineural loss

    • Right acoustic tumor

    • Brainstem lesion

    • Left facial nerve disorder

    • Left middle ear disorder


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Auditory Brainstem Response (ABR)

  • Measures brainstem response to a auditory stimulus

  • Wave pattern consisting of 5 positive peaks; distance between peaks indicates the amount of time between stimulus and response


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Otoacoustic Emissions (OAE)

  • Measure of the function of the outer hair cells (OHC) of the cochlea

  • Useful for

    • Infant screening

    • Pediatric assessment

    • Monitoring cochlear function


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Put it all together…

  • By using a combination of behavioral, electroacoustic, and electrophysiological testing through individual analysis and crosschecking, a proper diagnosis and treatment of audiological disorders can occur


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The End

…or is it?


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