Hearing tests Flashcards
What are tuning fork tests used to differentiate between?
Sensorineural and Conductive hearing loss
What is Rinne’s test?
Put vibrating fork next to ear and on bone behind
Conductive hearing loss - BC>AC (Rinne’s negative)
Sensorineural hearing loss - AC>BC if heard (Rinne’s positive)
Rinne’s positive is normal as Air conduction should be greater than bone conduction
What is Weber’s test?
Put vibrating fork on the middle of the patients forehead. Should sound equal.
Sensorineural - localise away from side of damage
Conductive - localise towards side of damage
Why does conductive hearing loss localise to the side of damage in Weber’s?
Conductive loss block out background noise so vibrations amplified
What is a pure tone audiogram?
Test used to assess threshold of hearing at various frequencies
Where should a pure tone audiogram be conducted?
In a sound proofed booth
How is a pure tone audiogram performed?
Tones are played at different frequencies to each ear. The quietest tone that can be reliably heard is marked on the audiogram. Higher the decibel number, go down on y axis - louder noise. Higher the line, better hearing
What is considered normal hearing?
Anything less than 20dB
How do you test air and bone conduction in a pure tone audiogram?
Air - headphones
Bone - Bone conductor on mastoid
How are conductive and sensorineural hearing loss seen on pure tone audiogram?
Conductive - normal bone conduction, reduced air conduction
Sensorineural - reduced air and bone conduction
How would you investigate a unilateral sensorineural hearing loss?
MRI to look for lesions on the pathway
What is presbycusis?
Hearing loss due to aging
What is a tympanogram?
Test to measure compliance of tympanic membrane
Give info about tympanic membrane, middle ear and eustachian tube function
How are the results of a tympanogram plotted?
y axis - compliance
x axis - pressure (daPascals)
When does compliance of the tympanic membrane peak?
pressure in external ear canal = middle ear
What are the 3 types of tympanogram tracing?
A - normal, peak at 0 daPascals
B - flat tracing
C - peak at negative pressure
What does a type B tympanogram tracing suggest?
Middle ear effusion - volume around 1cm3
Perforation - volume much higher
What does a type C tympanogram tracing suggest?
Eustachian tube dysfunction
What would cause a false negative Rinne’s test?
Severe unilateral hearing loss where skull crossover means bone conduction can be heard in the normal ear
How would you straighten out the ear canal for otoscope?
Pull ear up and out - adults
Down and back - children
How is compliance of the tympanic membrane measured?
Vary amounts of pressure given to external canal - compliance peak when this is equal to pressure in middle ear
How is sensorineural hearing tested in pure tone audiometry?
Bone conductor at mastoid - this can pass through to contralateral cochlea
Noise is played in contralateral ear to prevent this
What hearing test is used for newborns?
Otoacoustic emissions - should be part of newborn hearing screening program
Computer generated click played through small earpiece. Presence of soft echo indicate healthy cochlea
How is hearing tested in newborn/infants?
Auditory brainstem response test - if abnormal otoacoustic emissions test
How is hearing tested in 6-9month old children?
Distraction test - req. 2 trained staff
How is hearing tested in >2.5yo’s?
Speech discrimination tests - use similar sounding objects
How is hearing tested in >4yos?
Pure tone audiometry - done at school entry
