Hearing Loss

Basic Audiology Information

By El Eshun

Anatomy of the Ear

1. Outer ear 2. Middle ear 3. Inner ear 4. Central hearing

Anatomy of the EarAuditory processing Difficulties

Anatomy of the Ear

Auditory neuropathy/dysynchrony

Anatomy of the Ear

Sensorineural Hearing Loss

Anatomy of the Ear

Conductive Hearing Loss

TYPE CONDUCTIVE

SENSORI NEURAL

RETROCOCHLEAR

MIXED

PROGRESSIVE

BILATERAL

UNILATERAL

HIGH FREQUENCY

SLOPED

Degrees of Hearing LossNormal – 0-20 dB

Mild - 21-40 dB

Moderate - 41-55 dB

Moderate – Severe – 56-70 dB

Severe – 71-90 dB

Profound – 91+ dB

Audiological AssessmentsOtoscopy

Tympanometry

Audiometry

Auditory Brainstem Response (ABR)

Otoacoustic Emissions (OAE’s)

•Otoscopy is an examination that involves looking into the ear with an otoscope in order to examine the 'external auditory canal‘ , the outer ear and the ear drum

•The outer ear is inspected for signs of disease that may relate to the symptoms.

•Abnormal findings of the outer ear may include:

eczema. (otitis externa). wax obscuring the eardrum. Something lodged in the ear

Examination of the eardrum

The normal eardrum appears pinkish-grey in colour and is approximately circular in shape.

abnormal findings seen with the otoscope include

a hole (perforation) in the eardrum,

acute infection of the middle ear (acute otitis media). Sometimes in acute otitis media the eardrum will burst, allowing the pressure (and the pain) to reduce. Then one can often see the tear in the drum as well as the discharge in the outer ear. In the majority of people such a tear will heal completely.

Inserted grommet

Otoscopy

Tympanometry

Audiometry Auditory Brainstem Response

(ABR)

Otoacoustic Emissions (OAE’s)

Tympanometry

Tympanometry or immittance Audiometry is used to check the movement of the eardrum.

Tones are "bounced" off the ear drum/tympanic membrane to determine the amount of sound that is reflected back through the ear canal.

If the tympanic membrane is very stiff (eg. with middle ear effusion) then a lot of the sound is reflected back. When the tympanic membrane moves normally, very little of the sound is reflected.

Tympanometry in the Audiological Report

The pink boxes indicate whether it is a normal tympanogram if the peak falls within the box then the trace is normal

The pink boxes indicate whether it is a normal tympanogram if the peak falls within the box then the trace is normal

The 5 most common Tympanograms

Normal Tympanogram- normal mobility and middle ear pressure

Reduced TM mobility and normal ME pressure; consistent with presence of otosclerosis. Represents stiff ME system.

Hypermobility of eardrum and normal ME pressure; consistent with flaccid eardrum or disarticulation of ossicular chain.(3 bones of the middle ear)

Reduced TM mobility; consistent with presence of fluid in the middle ear space.

Normal eardrum mobility and negative Middle Ear pressure means that the eardrum is sucked in (retracted); consistent with eustacian tube dysfunction.

Otoscopy

Tympanometry

Audiometry

LINGS Auditory Brainstem Response

(ABR)

Otoacoustic Emissions (OAE’s)

AUDIOGRAMA standard way of representing a person's hearing loss or level.

Most audiograms cover the limited frequency range 100Hz to 8000Hz (8kHz) which is most important for clear understanding of speech.

They plot the threshold of hearing relative to a standardised curve that represents 'normal' hearing, in dBHL.

A sound is played at a range of frequencies and loudness levels and the client must show some type of reaction to indicate that the sound has been detected

Pure tone audiometry – When you hear a sound press a button to confirm thisConditioned play audiometry – when you hear the sound e.g put the man in the boatVisual reinforcement Audiometry – the sound is initially played together with the appearance of a toy then alone and childs seeking behaviour for the toy is recordedBehavioural observation Audiometry – spontaneous reactions are watched in response to sound e.g. blinking

With hearing aids

Left ear air conductionRight ear air conduction

Listening through the bones of the skull therefore bypassing the middle ear

Listening through headphones or insert phones

Listening with hearing aids/implant with speakers

Bone conduction – not ear specific represents both ears. Always measured at these frequencies only. Any lower and the child is responding to vibrotactile stimulation (vibration) Results indicate a moderate -severe sensorineural loss binaurally (both ears)

Hearing levels with aids showing a mild to moderate loss

Left ear air conduction showing a sev-profound hearing loss

Right ear air conduction – showing a profound hearing loss

Right ear air conduction – showing a profound hearing loss

TympanometryNormal ear canal volume in children is between 0.2-2cm3

Compliance (movement)Maximum compliance of the middle ear system occurs when thepressure in the middle ear space is equal to the pressure in theOuter ear canal. The maximum compliance value occurs atthe highest peak of the curve on a tymp graph . Child max norm = 0.2-0.9ml

Normal middle ear pressure in children is between +200 and -400 dPA

TympanometryNormal ear canal volume in children is between 0.2-2cm3

Compliance (movement)Maximum compliance of the middle ear system occurs when thepressure in the middle ear space is equal to the pressure in theOuter ear canal. The maximum compliance value occurs atthe highest peak of the curve on a tymp graph . Child max norm = 0.2-0.9ml

Normal middle ear pressure in children is between +200 and -400 dPA

Most audiograms will have a key explaining what the symbols on the audiogram represent

The arrows indicate that thresholds (point of detection) could not be measured at these frequencies

The arrows indicate that thresholds (point of detection) could not be measured at these frequencies

Otoscopy

Tympanometry

Audiometry

LINGS Auditory Brainstem Response

(ABR)

Otoacoustic Emissions (OAE’s)

Lings

EE, OO, AAH, S, SHH, M

Detection

Discrimination

Identification

The 6 sounds that are distributed across the frequencies for speech

Initially the aim is for your child to show they heard these sounds at normal conversational loudness levels then more quieter levels

Once your child can detect them all they then need to be able to tell the difference between the sounds

Lastly your child should tell you which sound is being presented

Otoscopy

Tympanometry

Audiometry

LINGS Auditory Brainstem Response

(ABR)

Otoacoustic Emissions (OAE’s)

ABR

The ABR test is a useful tool for measuring hearing when other hearing tests cannot be used.

The ABR test is reliable, objective, non-invasive and painless. Brain wave activity in the listening centers of the brain is recorded in response to a series of clicks presented to each ear. The ABR test indirectly estimates the level of hearing in the middle ear and inner ear.

Because of the nature of this testing procedure, the ABR test does not rely on any form of subjective response from your child.

ABR is used:

as a screening procedure for newborns who are at risk for hearing loss.

as a diagnostic tool to identify infants and small children with a hearing loss.

to estimate hearing levels in difficult to test patients, i.e., children with significant learning difficulties, autistism, children with developmental delay.

to evaluate children with suspected retrocochlear causes. Ie Auditory neuropathy and Auditory Processing Difficulties

to evaluate patients with Meniere's disease or similar disorders.

PROCEDURE

The ABR test is performed on an individual who is resting quietly or in a sleep state.

A series of clicks are presented to each ear through special earpieces inserted into the ear canals.

The audiologist can vary the intensity of the clicks. The individual wears a headband which records appropriate

brain wave activity. The averaging computer in the ABR unit then analyzes the

information and it is compared to normal responses. This procedure does not cause any discomfort to the person.

The test takes approximately one to two hours

Otoscopy

Tympanometry

Audiometry

LINGS Auditory Brainstem Response

(ABR)

Otoacoustic Emissions (OAE’s)

An otoacoustic emission (OAE) is a sound which is generated from within the inner ear. Their existence was first demonstrated experimentally by David Kemp and they have since been shown to arise by a number of different mechanisms within the inner ear. Numerous studies have shown that OAEs disappear after the inner ear has been damaged, so OAEs are used in the clinic as a measure of inner ear health.