Investigations Flashcards
what is the first line investigation for hearing loss?
pure tone audiometry (PTA)
how is pure tone audiometry carried out?
soundproof room with sound produced via headphones/earphones (air conduction) or bone conductor (bone conduction)
patient presses a button when sound is heard
what is masking?
technique used in PTA to isolate the test ear
narrow band noise played in non-test ear
pitch of vowels
low
pitch of consonants
high
mild hearing loss result on PTA
20-40
moderate hearing loss result on PTA
40-70
severe hearing loss result on PTA
70-90
profound hearing loss result on PTA
90-120
SNHL result on audiogram
no significant gap between air and bone conduction thresholds
what causes permanent SNHL?
damage to hair cells and/or hearing nerve
what naturally happens to the cochlea in ageing?
it is damaged
causes of SNHL
exposure to loud sounds ototoxic drugs infections (rubella) complications at birth tumour of auditory nerve (vestibular schwannoma) genetics
what do people with SNHL struggle to understand?
speech
is SNHL reversible?
no
CHL result on audiogram
significant gap between air and bone conduction thresholds where bone is within normal limits
what causes CHL?
sound cannot pass into the inner ear due to abnormalities with the middle and external ear e.g. infection
what is mixed hearing loss result on audiogram?
significant gap between air and bone, but bone is not within normal limits
causes of mixed hearing loss
genetics
birth defects
what is tympanometry used for?
test condition of the middle ear by creating pressures in ear canal
why is tympanometry helpful in OME?
demonstrates presence of middle ear fluid and tympani membrane perforation by showing a large ear canal volume
