Week9 Flashcards
Structure that generates OAEs
Outer Hair Cells
Absent OAE
-Conductive Loss
-Moderate to profound sensorineural loss
-
Present OAE
-Normal
-if issue lies beyond outer hair cells (inner hair cells, auditory nerve, brainstem, cortex)
May or may not be present OAE
Mild sensorineural hearing loss
DPOAE Stimuli
two pure tones, f2 is 1.2 times higher than f1, f1 presented at 65 db HL, f2 presented at 55 dB HL
Frequency at which DPOAE occurs
2f1-f2
o If given an amplitude and noise value, determine if DPOAE is present or absent
singal to noise ratio must be at least 6 dB to be considered present.
ABR wave matching
Wave I = peripheral(distal) portion of auditory nerve,
Wave II=Central (proximal) portion of auditory nerve,
Wave III= cochlear nerve,
Wave IV=Superior olivary complex,
Wave V=Lateral lemniscus
How ABR wave latency changes with intensity
latency increases as intensity decreases
Definition of ABR threshold
lowest stimulus intensity that results in a wave V- Wave V persists down to threshold but waves I-IV disappear
What ABR threshold is used for
to estimate a pure tone audiogram, both air conduction and bone conduction can be done to estimate thresholds.
Normal Hearing ABR
Latencies normal, thresholds normal.
Conductive Loss ABR
All latencies abnormally long, thresholds outside normal range.
Sensory (cochlear loss) ABR
Latencies are normal, thresholds outside normal range.
Neural (retrocochlear) Loss ABR
Latencies of normal waves are abnormally long, thresholds are outside normal range, response may be grossly abnormal or absent
How tumors of the auditory nerve affect the ABR
presence of tumor affects brainstem transmission time, tumors can cause abnormally long interpeak latencies
What the 1-3-6 guidelines refer to
1: hearing screening should take place by 1-month,
3: Children who refer on the screening should receive a diagnostic evaluation by 3 months,
6: Children diagnosed with hearing loss should receive intervention by this age.
When a baby would be referred for a diagnostic evaluation
-initial screen and rescreen;
-parent/caregiver concerns about hearing, speech, and or/language;
-infant has risk factors for hearing loss
OAE infant screening Limitations
Some with mild sensorineural loss will pass, infants with neural hearing loss will pass, infants with fluid in outer/inner ear may refer
AABR screening limitation
Some infants with mild sensorineural loss may pass; infants with neural hearing loss will refer. There will always be overlap.
Procedures involved in a diagnostic evaluation for a 3-month-old
- Case history for child and family;
- Otoscopy;
- Tympanograms;
- Otoacoustic emissions (OAEs);
- Auditory Brainstem Response thresholds.
Hearing aids can be programmed with ABR thresholds, eventually we want to get a pure-tone audiogram, children with profound sensorineural loss will be referred for cochlear implant evaluation
Considerations for tympanometry probe tone frequency depending on age
-Under 6 mos., use 1000 Hz probe tone,
-above 6 mos. Use 226 Hz probe tone.
-Infant ear canal and middle ear properties different
Range of thresholds for slight hearing loss degree
16-25 dB HL
VRA age range
6 months to 2 years
