Hearing Tests Flashcards
What is the purpose of the Rinne’s and Weber’s tests?
Allow differentiation of conductive and sensorineural hearing loss
What principle guides the Rinne’s test?
Normally air conduction is better than bone conduction
In Rinne’s test, if bone conduction is better than air conduction, what does this suggest?
Conductive hearing loss
How is Rinne’s test performed?
Place tuning fork on mastoid process until patient tells you they can no longer hear it. Quickly bring it in front of the external auditory canal. Ask if they can still hear it.
Should be louder in front of the EAC (air conduction better than bone)
What principle should be remembered in order to understand Weber’s test results?
External noise muffles bone conduction
For Weber’s test, in unilateral conductive deafness, where is sound lateralised to?
Loudest on AFFECTED side
In conductive hearing loss, external noise is blocked on that side, so bone conduction not muffled
For Weber’s test, in unilateral sensorineural deafness, where is sound lateralised to?
Sound is localised to UNAFFECTED side
How is Weber’s test performed?
Tuning fork placed in the middle of the forehead equidistant to the patient’s ears. The patient asked which side is loudest.
What tuning fork is used in Weber’s and Rinne’s test?
512Hz
Where is the pathology in conductive hearing loss?
External or middle ear
Where is the pathology in sensorineural hearing loss?
Inner ear or CNVIII
What can cause conductive hearing loss?
Impacted wax Otitis media Otitis media with effusion Otitis externa Otosclerosis
What can cause sensorineural hearing loss?
Presbyacusis
Meniere’s
Acoustic neuroma
Ototoxic medication
Is it more helpful to do the Rinne’s or Weber’s test first?
Doesn’t really matter, but do Rinne’s first - establish if there is conductive hearing loss. If air conduction better than bone on both sides then do Weber’s to see if sensorineural problem
What does Rinne’s test result show in sensorineural deafness?
Air conduction better than bone
Before starting otoscopy examination, what should you do first?
Ask if patient has any ear discomfort - if so examine non painful side first
Ask which is the ‘better’ ear and examine this first to act as a marker for comparison
Test otoscope to check it works
If patient has infection, change speculum on otoscope before examining other ear
What does the pure tone audio gram test?
The hearing thresholds of patients at different frequencies.
The most widely used assessment of patient’s hearing
Can be used from around 4 years upwards
What happens during a pure tone audio gram test?
In a sound proof booth
Tones played to patient at different frequencies to each ear
Each frequency tested a number of times and the quietest tone that can be reliably heard is marked on the audiogram
What are the axis labelled on an audiogram?
Frequency in hertz on x axis
Decibel scale on y axis with 0 at the top and increasing decibels (loudness) as you descend the y axis.
The higher the line on the pure tone audiogram means…
Better hearing
Anything above what on the audiogram is considered normal?
20bD
What is an air bone gap?
In conductive hearing loss the audiogram has normal bone conduction and reduced air conduction thresholds ie there is a gap between the 2 lines
Is there an air bone gap in sensorineural hearing loss?
No - the audiogram will have reduced air and bone conduction thresholds
What is a tympanogram?
Test that measures compliance of tympanic membrane. Gives information about TM, middle ear and Eustachian tube function.
How is a tympanogram done?
Probe inserted into external ear canal
Takes seconds to perform
Done at any age
In a tympanogram what is measured on the x and y axis?
X axis = pressure (daPascals)
Y axis = compliance of TM
What is the process involved in doing a tympanogram?
Varying amounts of pressure created in external ear canal. The probe seals the canal.
In a tympanogram, when does compliance peak?
When the pressure in the canal equals that of the middle ear
How many tympanogram tracings are typically seen?
3
What is a type A tympanogram?
Normal result
Peak centred on 0 daPa on x axis
What is a type B tympanogram?
Flat tracing
Suggests middle ear effusion or perforation
How do you differentiate effusion from a perforation on a type B tympanogram?
By looking at the canal volume reading on side of tympanogram. An effusion will have a normal canal volume - around 1cm3 whereas a perforation the volume will be larger (it is measuring the middle and external ear volume)
What does a type C tympanogram suggest?
Eustachian tube dysfunction
In a type C tympanogram, does the peak of the tracing have a negative or positive pressure?
Negative
In sensorineural hearing loss are both air and bone conduction impaired?
Yes
Are vowels high or low pitch?
Low
In an audiogram, if both air and bone conduction for one ear are below 20dB and the is an air bone gap, what does this suggest?
Mixed hearing loss
What is Cahart’s notch?
A dip seen on audiogram at 2000Hz (masked bone conduction) indicating otosclerosis
What is masking? (Done on audiogram test)
In cases of asymmetrical hearing loss, cannot be certain that the intended ear is the one detecting the sound. Masking noise used to occupy the ear not being tested to prevent this occurring.
On an audiogram, how does presbyacusis appear?
Down slopping curve - loss of high frequency (both air and bone conduction)
Ototoxicity can show a similar shaped curve
How does noise induced hearing loss typically appear on audiometry?
Typically shows a notch at 3,4 or 6 kHz with recovery at 8kHz
(Down then back up)
If the air and bone conduction ipsilaterally reduces at high frequency, what should be considered?
Right or lift sided high frequency sensorineural hearing loss
- acoustic schwannoma
- CP angle tumour
A low frequency ipsilateral sensorineural hearing loss is typically seen in…
Ménière’s disease
For audiograms, what rules should be followed?
Anything above 20bB is normal
In sensorineural hearing loss, both air and bone conduction impaired
In conductive hearing loss only air conduction impaired
In mixed - both air and bone conduction impaired, with air often ‘worse’ than bone
