Week 10: OAEs and audiogram Flashcards
1
Q
discordance vs concordance of test batteries
A
- discordance= the inconsistency between two or more test procedures
- concordance= the consistency between two or more test procedures
- –discordance between the PTA and WRS can help identify retrocochlear pathology
- –discordance also underlies the differential diagnostic capability of objective tests like OAE measurement
2
Q
strengths of OAEs in clinical practice
A
- objective measure:
- –require no behavioral response
- –uninfluenced by patient motivation, cognitive status, state of arousal, pt’s native language, motor status
- very sensitive to OHC dysfunction
- valid test for infants and young children*brie test
3
Q
weaknesses of OAEs and clinical practice
A
- not a true measure of hearing
- abnormal finding does not invariably indicate hearing loss
- as a single measure generally provides limited info on hearing loss
- no info on speech perception or understanding
4
Q
TEOAEs for normal vs hearing impaired
A
- optimize distinction between normal and impaired cochlear function
- –80-82 dB peSPL for click stimuli
- interpreting result
- –overall hearing is better than 20 dB HL (TEs are present in 99% of ears)
- –SNHL greater than 40 dB HL (TE are always present)
- –SNHL 25-35 dB HL (maybe present, but mostly absent)
- –SNR of less than 6 dB and reproducibility of less than 70%= detect 96% of patients with hearing threshold more than 20 dB HL
- –sensitive to hearing loss at 1000-4000 Hz
5
Q
DPOAES: normal vs hearing impaired
A
- primary stimulus levels
- –optimal level: L1 between 50-70 dB SPL, L2 10-15 dB softer
- —–best to differentiate hearing and hearing loss: L1 of 65 and L2 of 55
- —-other reports show lower levels are more sensitive to HL, but fewer responses
- high level (70-75 dB) stimulation cause more response and more artifact
- –not as accurate of eval of hair cell function
- present with thresholds under 20
- with SNHL over 50 they are always absent
- SNHL 25-45 may be present
- normative data (L1 of 65 and L2 of 55)
6
Q
TEOAE vs DPOAE
A
*generally if one is present the other will be as well
*changes in either from baseline of 4 dB or more shows changes in cochlear or middle ear function
*choosing a test based one the purpose
*sensitivity to hearing loss:
—1000 Hz= TEs
2000-4000= DP and TE
4000-6000 DP
7
Q
ecochg
A
- helpful in differential dx because it allows to record potentials from the cochlea and auditory nerve
- cochlear microphonic
- summating potential
- compound action potential
8
Q
OAEs vs CM
A
- both evaluate OHCs
- CM
- –not very frequency specific
- —-moderate to loud stimuli result in increased basal-ward excitation of the traveling wave (making it harder to identify the site of lesion)
- OAEs
- –much easier to record
- –more frequency specific
- –however, OAEs are easily affected by hearing loss
9
Q
middle ear pressure and OAEs
A
- changes in middle ear pressure will change transmission characteristics (highest amplitude at 0 daPa)
- ME pressure reduces emission amplitude
- –TEOAEs are generally not detected in case of pressure worse than -200daPa
- low freqs are affected more than high because you are adding stiffness to the system so low freqs suffer and highs travel easier
10
Q
ventilation tubes and OAEs
A
- presence of a response is related to time since surgery and tube type
- –if TEs are tested immediately, less likely to be present (20%)
- –if testing about a month after surgery, more likely to be present (80%)
- –DP amplitude increases right after surgery and keeps increasing
- –grommets dont affect response as much as t-tubes
- with an open tube and no pathology, OAEs can be recorded, but the amplitude us likely to be reduced, especially at low freqs
- normal OAEs indicate the tube is open and there is no middle ear pathology and functioning OAEs
11
Q
TM perforation and OAEs
A
can be recorded if there is a small perf
- amplitude may not be affected, but is likely reduced
- if active otitis media exists, OAEs should not be recorded
12
Q
OAEs with otitis media
A
- DPs and TEs are usually absent with OM
- –forward transmission can be compensated for by increasing stimulus levels
- –can’t really compensate for loss in backward transmission, except to try to reduce noise floor
- children with Downs often have absent OAEs, which may be due to poor ME function of SNHL
- of OAEs are present, it would be reduced in amplitude depending on:
- –Small A-B gap
- –stimulus frequency frequency
- –amount of effusion
- DP absence is related to the thickness of the fluid
13
Q
4 reasons ongoing screening is important
A
1) the inpact of hearing loss in children can adversely affect social development, language acquisition, emotional and psychosocial status, and early pre-academic skills
2) preschool screening allows detection of young children who were missed
3) detect progressive or delayed onset cochlear hearing loss
4) ongoing screening efforts help detecting recurrent conductive hearing loss
14
Q
OAEs and preschool/school screenings
A
- hearing screening for preK and school kids is generally pure tone audio with test freqs at 1,2,&4
- using SNR criteria–too many false negative (misses) for preschool and school age children
- –DPOAE screening (using a fixed SNR of 6 or greater) can miss up to 38% of children who failed puretone testing
- using more rigorous criteria for pass outcome:
- –greater than 6 dB SNR and DP amplitudes above 0 dB SPL
- –higher false positives leading to more hearing testing, not as costly as infants
15
Q
OAEs diagnostic value
A
- offer site-specific info in genetic disorders
- indicate subclinical dysfunction (risk for HL)
- combined with other electrophys measures gives more info about where damage is
