Chapter 33 - Hearing Evaluation Flashcards
Which test measures ability to understand speech
discrimination test
Pure tone average
Air conduction at speech freq
500, 1000, 2000
Masking
simultaneous presentation of sound to non-test ear
Stenger test
r/o malingering when 20dB difference between ears
tone 10dB above threshold given to better ear
Simultaneous tone 10dB below threshold to poorer ear
Patient should respond if HL is genuine
Malingering patients will not respond: + test
What is Hertz?
cycles/second
Weber test: two questions
Where they hear it?
Is it louder in one ear or another?
Negative Rinne
Sound heard louder at mastoid, BC>AC, sign of CHL of at least 25 dB (some say 15-20)
If equal or louder at EAC, its a positive test (NL)
Schwabach’s tuning fork test
Place on pt mastoid until can’t hear
then place on the mastoid of someone with NL hearing
If they can hear it, report test as “diminished”, indicating SNHL
Frequency spectrum for normal hearing
Human ear: 20-20,000 Hz
Typical adult: 200-10,000 Hz
Speech: 400-5000 Hz
Audiometric test: 250-8000 Hz
Decibel
hearing: db HL
environment: db SPL (sound pressure level)
Logarithmic scale
0 dB HL is normal hearing across entire frequency spectrum (HL meaning hearing level)
Normal hearing at 125 Hz vs 1000 Hz vs 6000 Hz
125- 45 db SPL
1000- 7 dB SPL
6000- 16 dB SPL
Hearing loss thresholds and severity
25-40: Mild
40-60: Moderate
60-80: Severe
>80: Profound
Symbols on audiogram
Unmasked AC: X (L), O (R)
Masked AC: square, triangle
Unmasked bone conduction: open to my left/right
Masked bone cond: open to my left/right
What does threshold mean
Patient perceives sound stimulus 50% of the time at that dB
Fletcher’s average
Use two best of the pure tone average frequencies
For patients with precipitously sloping HL
Normal air-bone gap
approximately equal (<10 dB difference) SNHL does not have air bone gap >10dB
Speech recognition threshold
lowest dB at which patient correctly identifies the word in 50% of the presentations
Should be within 7dB of PTA/Fletcher’s average
Speech discrimination/recognition test
Present words at 40dB above SRT, or at pt most comfortable loudness
Percentage of words correctly identified (out of 25)
Good is 80-100%
Can do in presence of background nosie to estimate functional performance with and w/o HA/CI
Immitance test battery
tympanometry
acoustic reflex measurements
Tympanometry: how it works
compliance of TM maximum when pressures equal
Peak pressure = middle ear pressure, nL 0 to -150
Tympanogram types
A- NL
As- stiffer (low compliance), otosclerosis
Ad- more flaccid (higher compliance), oss discont
B- flat, no pressure peak. Immobile. eff/perf
C- peak less than -150, ETD
Differentiate type B effusion vs perf
look at ear canal volume
High = perf (included middle ear)
Normal vol in kids is 0.5-1cm^3, in adults up to 3
Acoustic Reflex
Loud sound –> stapedius (b/l) and tensor tymp –> stiffen ossicles, DEC TM compliance
Stapedius: attach to posterior crus stapes, pulls stapes from oval window
TT: pull malleus in toward middle ear
Decreases loud sounds 20dB over threshold by 15dB
Decreases vocalization sound by 15dB
Acoustic reflex neural pathway
cochlea –> CN VIII –> cochlear nucleus –> trapezoid body –> Sup Olive Complex –> CN VII nucleus –> stapedius m
Crossover at sup olive to contralateral cochlear nucleus for contralateral pathway and contraction of stapedius
How is ABR conducted
Baby relaxed
Scalp electrodes for EEG
Clicks/tones through earphones –> evoke electrical potentials that are measured
How to interpret ABR waves
Mnemonic E COLI I- Eighth CN II- Cochlear nucleus III- Olivary complex Sup IV- Lateral lemniscus V- Inf colliculus
Tumor delays waveform at site of lesion
Auditory neuropathy is absent Wave I
Auditory Steady State Response
Can be louder than ABR, good for differentiating severe from profound HL
Frequency-specific tonal stimulus
What do OAE’s measure?
sound produced by cochlea following acoustic stimulation
Do not measure neural function
Transient evoked and Distortion product
Ways to tell if someone is feigning HL
For unilateral HL, sound should cross over somewhere between 40-70 dB and be detected in poor ear with AC
With BC, sound crosses over to poorer ear as its interaural attenuation is 0 dB
PTA-SRT/SAT should agree
