Causes of Hearing Impairment Flashcards
What are the 3 part of the ear?
outer ear: pinna
middle ear: tympanic membrane and ossicles
inner ear: cochlear
What is the main audio function of the ear?
Conversion of audio waves -> vibrations -> APs (interpretation by brain)
What are the 2 mean functions of the ear?
- hearing (audio)
- balance (vestibular)
What are the main steps in performing otoscopy?
- gain consent
- look at the good ear first to set baseline
- look at outer ear and behind pinna for scars, deformities
- look down ear canal, light reflex (cone of light) and each part of the TM
What are the major otoscopic landmarks seen at the TM?
- Pars flaccida (most superior aspect)
- manubrium of malleus (at 12 o’clock)
- long process of incus (faint ouline adjacent to the malleus)
- Annular ligament (outer structure) encompassing the TM
- Umbo (lowest bulb of the malleus)
- light reflex (cone of light)
What are the 3 types of hearing loss?
- conductive (outer or middle ear)
- sensorineural (inner ear)
- mixed (outer/middle ear + inner ear)
What are the tuning fork tests?
bedside tests used to determine whether hearing loss is conductive or sensorineural
(if no access to audiometry)
uses 512Hz tuning fork
2 types: Rinne’s and Weber’s
What is the Rinne’s test?
place the tuning fork in front of the ear and on the mastoid price and ask
“is it louder in front or behind?”
this is measuring air conduction (‘in front of ear’) vs. bone conduction (‘on the mastoid, behind the ear’)
normally AC > BC
What are the outcomes of a Rinne’s test?
AC > BC RINNE'S TEST POSITIVE - normal or - mild-moderate sensorineural hearing loss on the ipsilateral side
BC > AC (i.e. louder behind on mastoid)
RINNE’S TEST NEGATIVE
- conductive hearing loss on the ipsilateral side
or
- severe-profound sensorineural hearing loss on the ipsilateral side
What is the mechanism behind a Rinne’s negative conductive healing loss on the ipsilateral side?
ie BC > AC
due to the conductive hearing loss
better when sound going straight to cochlear via the mastoid process rather than going via the outer/middle ear
What is the mechanism behind a Rinne’s negative, severe sensorineural hearing loss on the contralateral side?
i.e. BC > AC
due to defects in the inner ear (causing severe hearing loss)
sound transmitted through the mastoid and then the skull and then heard on the other ear
What is the Weber’s test?
place tuning fork on midline of forehead and ask pt
“is it loudest on the right, left or middle?
checks which ears are affected by hearing loss
lateralised loss would indicate conductive on that side or sensorineural on the other side
What are the outcomes of the Weber test?
DOES NOT LATERALISE
- normal hearing
or
- symmetrical mild-moderate hearing loss
LATERALISES
- conductive hearing loss on ipsilateral side
or
- sensorineural hearing loss on contralateral side
What kind of hearing loss would perforation of the tympanic membrane cause?
conductive hearing loss (as affecting middle ear)
would cause lateralised hearing
What would normal bilateral hearing or bilateral sensorineural hearing loss look like in Rinne and Weber tests?
Rinne: positive bilaterally (AC>BC)
Weber: central (both sides would lateralise so the average would be central)
