Session 2 Audiology

Question 1

what are tuning fork tests (type of subjective test)?

Answer 1

Measurement of auditory response to sound generated via a tuning fork.

Assess gross symmetry of hearing and determine presence / absence of conductive deficit.

Sound transfer by air conduction is more efficient than that by bone conduction

Question 2

tuning fork tests that can be used?

Answer 2

Weber test- Assesses symmetry of hearing.Strike the tuning fork (256 / 512 Hz).Place tuning fork firmly on a bony point of the head, along the midline (usually vertex or bridge of nose). Ask patient to indicate in which ear, if any, the sound is loudest.

Rinne test- Compares hearing through air and bone conduction.

Strike the tuning fork and hold base against mastoid bone, for 2 to 3 sec.

Bring tuning fork to external ear canal.

Ask patient which position gave loudest perceived sound.

Question 3

what is indicated by the sound being of the same loudness in both ears in a Weber test?

Answer 3

normal hearing, or bilateral symmetrical hearing loss

Question 4

what is indicated by the sound being louder in the left ear in a Weber test?

Answer 4

left ear conductive loss, or right ear sensory/neural loss

Question 5

results of rinne test in patient with conductive hearing loss?

Answer 5

bone conduction will be greater than air conduction, so sound heard loudest when base of tuning fork held against mastoid bone. (rinne -ve)

Question 6

results of rinne test in patient with sensorineural hearing loss?

Answer 6

sound heard loudest by air conduction (when tuning fork held next to external ear canal) as sound transfer by air conduction more efficient than by bone, and in this hearing loss, both air and bone conduction are equally reduced. sound also heard loudest by air if normal

Question 7

false -ve in a rinne test?

Answer 7

Non test ear detects sound by bone conduction (requires masking).
No / very poor cochlear function in test ear
can occur in sensorineural hearing loss patients

Question 8

advantages of tuning fork tests?

Answer 8

simple, minimal cost- minimal equipment

Question 9

disadvantages of tuning fork tests?

Answer 9

Tests do not quantify degree of hearing sensitivity.
Results influenced by technique of tester.
Masking of the non test ear required to prevent a false negative Rinne test in cases of unilateral hearing loss
don’t know if bilateral hearing loss?

Question 10

difference between subjective and objective techniques?

Answer 10

Subject is asked to provide a response to a stimulus. Measures perception but requires patient co-operation. Gold standard, but no figure produced.

Objective: Recordings are made of physiological responses to stimuli, without the need for conscious patient acknowledgement.

Question 11

function of external ear?

Answer 11

modifies sound- localises it so know if up, down, front or behind
collects sound
conducts sound to tympanic membrane- forms partition between meatus of external ear and tympanic cavity of middle ear

Question 12

components of external ear?

Answer 12

auricle (pinna) which collects sound, and external acoustic meatus (canal), which conducts sound

Question 13

middle ear function?

Answer 13

impedence matiching: must offset the decrease in acoustic energy that would occur if the low impedance ear canal air directly contacted the high-impedance cochlear fluid. When a sound wave is transferred from a low-impedance medium (eg, air) to one of high impedance (eg, water), a considerable amount of its energy is reflected and fails to enter the liquid.

Question 14

how does middle ear match impedence?

Answer 14

lever action of bones- auditory ossicles
area of eardurm (tympanic membrane) much greater than that of oval window
conical shape of eardrum

These all act to build up pressure for vibrations to move through fluid

Question 15

what is otoscopy?

Answer 15

subjective examination where otoscope used to visualise external and middle ear. Handle and head, head has a light source. Can examine ear canal and tympanic membrane- pars tensa and pars flaccida.
Can diagnose otitis media and otitis externa

Question 16

what is tympanometry?

Answer 16

objective test: provides a measurement of tympanic membrane / middle ear integrity, pressure and impedance.
Pure tone (226 Hz*) is played into the ear canal and its intensity is monitored whilst static pressure is applied and varied (*1000 Hz for neonates).
Maximum compliance occurs when applied pressure in external ear canal equals that within the middle ear cavity.
Results usually expressed as compliance (reciprocal of stiffness component).
The instrument changes the pressure in the ear, generates a pure tone, and measures the eardrum responses to the sound at different pressures. This produces a series of data measuring how admittance varies with pressure, which is plotted as a tympanogram.

Question 17

advantages of tympanometry?

Answer 17

quick and simple test, minimal cooperation needed from subject

Question 18

disadvantages of tympanometry?

Answer 18

Test probe must make an airtight seal against the ear canal.

High frequency probe tone (1000Hz) needed for neonates- may be painful?

Question 19

what is the bony labyrinth suspended in, and what are its components?

Answer 19

perilymph

labyrinth comprises cochlea, vestibule and semicircular canals

Question 20

what does the membranous labyrinth contain?

Answer 20

endolymph

Question 21

what may cause neural dysfunction?

Answer 21

an acoustic neuroma

Question 22

what is a recruitment defecit?

Answer 22

often cochlear origin, quiet sounds cannot be heard, loud sounds heard at normal intensity or louder than normal (reduced dynamic range.)

Question 23

4 hearing defecits?

Answer 23

conductive
sensori-neural
recruitment
mixed

Question 24

what may be important components of history of patient prior to auditory examination?

Answer 24

otalgia
deafness- uni/bilateral, onset- sudden/graual, progressive/flucuating/improving, speech discrimination in noise
otorrhoea
vertigo
tinnitus

Question 25

what are psychophysical tests?

Answer 25

study relationship between stimulus-sound and sensation

Question 26

examples of psychophysical tests?

Answer 26

tuning fork tests
pure tune audiogram
speech audiometry
paediatric audiometry

Question 27

what is a pure tone audiogram?

Answer 27

type of psychophysical test
Measures auditory threshold (sensitivity) to ‘pure tones’ spanning a fixed range of discrete frequencies (250Hz to 8KHz).
Sound is presented via air or bone conduction.
Patient is asked to respond to appearance of sound.
Equipment functionality and calibration are standardised, as is test methodology (British society of Audiology recommended procedures). so same wherever done in country
0=average
-10= better than average
dropping off is normal in elderly

Question 28

advantages of a pure tone audiogram?

Answer 28

Provides a quantifiable measure of hearing sensitivity (across speech frequency range).

Measures perception not just function.

Results are standardised between centres.

Can differentiate between conductive, sensory / neural and mixed causes of hearing deficit.

Shape of ‘audiogram’ can provide an indication of underlying pathology.

Results used for diagnosis, treatment monitoring and rehabilitation approaches

Question 29

limitations of pure tone audiography?

Answer 29

High level of patient co-operation is required- patient must tell you whether they can hear something

Cannot obtain reliable results from subjects who are very young, older subjects with learning difficulties or those with ‘non-organic’ deficit.

Results are influenced by the technique of the tester.

A quiet test environment is required.

Masking of the non test ear required in cases of unilateral hearing loss.

Results are susceptible to ‘learning effects’.

Pure tone stimuli of limited relevance to everyday hearing tasks e.g. music and speech, so not good for assessing their hearing in everyday life

Question 30

sources of error in pure tone audiometry?

Answer 30

Environmental / body noise.

Concentration / motivation.

Tinnitus.

Tester technique.

Transducer placement accuracy (up to 15dB at <500Hz).

Learning effects / habituation / fatigue.

Equipment calibration (±3 to 5dB).

Test / re-test variability (3 to 7dB).

Question 31

what is speech audiometry?

Answer 31

another psychophysical test
Measures a persons ability to recognise speech sounds.

The patient is presented with pre recorded speech material (word lists), at a calibrated intensity, and asked to repeat what they hear.

Each word comprises 3 phonemes and the patient receives a point for each phoneme correctly identified.

A range of stimulus intensities are used to illicit scores below 10% and up to the patients maximum (hopefully 100%).

Question 32

advantages of speech audiometry?

Answer 32

Speech sounds are more ‘physiologically relevant’ than pure tones.

Results can help to differentiate between conductive, sensory and neural deficits.

Can help to identify ‘non-organic’ conditions.

Can help with rehabilitation procedures.

Question 33

disadvantages of speech audiometry?

Answer 33

Speech material is not available in all languages.

Results depend upon the degree of cooperation of the patient.

Procedure cannot be used with the very young or those who have limited understanding.

Question 34

describe paediatric audiometry

Answer 34

Subjective assessment of auditory function in young children (6 months +) using sound field audiometry.

Allows for early intervention where required.

Provides a ‘true measure’ of hearing ability.

6 to 18 months Distraction testing
18 to 30 months Cooperation testing
30+ months Performance testing

Question 35

what is distraction testing in paediatric audiometry- subjective testing using sound field audiometry?

Answer 35

a distractor distracts the child from looking where the sound will be coming from, to see whether the child looks in the direction of the sound when it is played

Question 36

sources of error in paediatric audiometry?

Answer 36

Visual cueing (shadows etc).

Tactile cueing (drafts etc).

Auditory cueing (clothing, jewellery etc.)

Olfactory cueing (perfume etc).

Distracter technique (over- understimulation)

Rhythmic stimulation.

Question 37

what is visual reinforcement audiometry?

Answer 37

used in children aged 1-3. sound presentation is followed by something visual e.g. a puppet, so child more likely to turn to sound when they hear it as they associate it with seeing something

Question 38

otoacoustic emissions are an example of objective testing, what are these?

Answer 38

An otoacoustic emission (OAE) is a sound which is generated from within the inner ear. OAEs disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and the clinic as a measure of inner ear health.

Broadly speaking, there are two types of otoacoustic emissions: spontaneous otoacoustic emissions (SOAEs), which can occur without external stimulation, and evoked otoacoustic emissions (EOAEs), which require an evoking stimulus.

Question 39

types of otoacoustic emissions?

Answer 39

Transient-evoked OAEs (TEOAEs or TrOAEs) are evoked using a click (broad frequency range) or toneburst (brief duration pure tone) stimulus.Distortion product OAEs (DPOAEs) are evoked using a pair of primary tones.
Stimulus sounds (clicks or multiple pure tones) are introduced into the EAM, whilst all sounds present within the canal are recorded acoustically.  

TEOAE stimulate then record, DPOAE stimulate and record simultaneously.

In cases where the cochlear is functional (above a specific sensitivity), a cochlear ‘echo’ can be detected acoustically within the ear canal.

Comparison between the frequency content of the stimulus and emission responses, (together with the self correlation of the emission), provides a measure of the functional integrity of the cochlear outer hair cells along the length of the basilar membrane

Question 40

advantages of otoacoustic emissions?

Answer 40

The procedure is non invasive, quick to administer and requires minimal patient cooperation.

Can be applied to patients of all ages from neonates onwards (used extensively for neonatal screening).

Provides a reliable indicator of the integrity of the peripheral auditory system.

Question 41

disadvantages of otoacoustic emissions?

Answer 41

Procedure cannot measure perception.

Data obtained only up to the level of the outer hair cells of the cochlea.

The technique is very sensitive to outer / middle ear pathology.

Results do not quantify cochlear sensitivity.

Responses abolished completely with hearing losses above ~30 – 40dB.

Question 42

what is electrocochleography?

Answer 42

Electrophysiological technique used to assess the functional integrity of the cochlea, objective technique.

Involves measurement of the electrical potentials originating from the cochlea / auditory nerve, evoked by acoustic stimulation of the cochlea.

Signal detection achieved using an electrode positioned in the ear canal (extra tympanic) or a needle electrode inserted through the eardrum (trans tympanic), compared to a skin surface reference.

Stimuli comprise acoustic clicks or brief tone bursts.

Technique can be used to determine cochlear sensitivity and for the investigation of cochlear pathologies (e.g. Menieres disease).

Cochlear Microphonic

Electrical activity reflecting the phase related component, of the cochlear hair cells, to the sound stimulus.

Summating potential

Baseline deflection – may represent a steady component of the hair cell receptor potential.

Compound action potential

Action potential generated by the auditory nerve fibres

Question 43

advantages of electrocochleography?

Answer 43

The test is ‘objective’ with no subjective patient response required.

As the response is considered ‘near field’, masking of the contralateral ear is not needed.

Responses are not influenced by sleep, sedation or general anaesthesia.

Can be used for intra operative monitoring of cochlear / nerve function.

Question 44

limitations of electrocochleography?

Answer 44

Does not provide information for function beyond the early segment of the auditory nerve.

Does not test perception.

Trans tympanic recording provides the greatest signal strength, however the procedure is invasive.

Normative data is required against which to compare patient results.

Cochlear function at frequencies below ~1KHz cannot be reliably obtained.

Question 45

what are auditory brainstem responses?

Answer 45

Involves measurement of the electrical potentials originating from the auditory nerve / brainstem pathways, evoked by acoustic stimulation of the cochlea.

Acoustic stimuli can include broad band clicks or tone pips, provided via headphones, insert phones or bone conduction.

The procedure is ‘objective’ and just requires the subject to relax sufficiently to minimise myogenic activity (usually requires sedation or GA for babies who cannot be tested under natural sleep).
signal extraction:
Differential amplification

Cancels signals from ‘distant origins’.

Signal filtering

Removes signals whose frequency is above or below predetermined limits.

Artifact rejection

Rejects samples of signal whose amplitude exceeds predetermined limits.

Signal averaging (time domain)

Allows cancellation of signals which are not ‘time locked’ to the stimulus.

Question 46

applications of auditory brainstem responses?

Answer 46

Neurodiagnosis of VIIIth nerve or brainstem lesions.

Newborn infant screening.

Estimation of ‘auditory’ threshold in young children and ‘difficult to test’ subjects.

Intraoperative monitoring of cochlear and VIIIth nerve function.

Question 47

advantages of auditory brainstem responses?

Answer 47

The test is ‘objective’ with no subjective patient response required.

Responses are not influenced by sleep, state of arousal, sedation or general anaesthesia.

Can be used for intra operative monitoring of cochlear / nerve function.

Latency measures show a large degree of inter subject similarity.

Question 48

limitations of auditory brainstem response?

Answer 48

The small signal size makes the technique sensitive to sources of interference (subject, equipment or environmental).

The subject needs to be relaxed or asleep.

It is not a test of perception.

No information is provided for pathway structures beyond the brainstem.

Result interpretation is influenced by conductive and sensory hearing disorders.

Question 49

what is the cortical evoked response?

Answer 49

Measurement of electrical potentials originating from ‘non specific’ cortical structures, evoked by acoustic stimuli.

Tone burst stimuli can be used to provide an objective, frequency specific, estimation of auditory sensitivity.

Procedure is of use for the evaluation of -

Patients who have given inconsistent or unreliable results to subjective testing.

Patients who are unable / unwilling to participate with subjective testing.

Medico-legal patients or those with suspected non-organic conditions

Question 50

application of cortical evoked response?

Answer 50

Technique provides objective estimation of frequency specific, auditory response thresholds.

Enables assessment of higher auditory function.

In the absence of cortical / perceptual deficit, frequency specific response thresholds can be obtained at intensities within 5 to 10dB of the patients subjective threshold (depending upon noise levels and subject mental alertness).

Question 51

limitations of cortical evoked response?

Answer 51

Does not test perception.

Responses show a large degree in inter- and intrasubject variability,

Responses are affected by the patient state of alertness therefore subjects need to be alert but without excessive muscle movement.

Cannot be performed in patients who are asleep, sedated or under GA.

Not suitable for paediatric testing.

Full test procedure requires extensive testing time (up to 1 hour).