Last bit for the Final Flashcards
sisi test basis
extension of the difference limen intensity (DLI) test
- rely on a patient’s ability to detech small changes in signal intensity
- the basis for the test: a person with cochlear lesion can recognize smaller difference limens for intensity than normal hearing individuals
- used to localize pathology to cochlea
dual excitation theory
abnormal growth of loudness
- occurs with cochlear lesions without damage to inner hair cells
- once the threshold of the inner hair cells of the cochlea is reached: the ear’s ability to detect small changes in intensity is improved= abnormal growth of loudness
sisi test procedure
detection of brief (200ms) 1 dB increments in a 20dB SL tone
- 20 trials of the 1dB increments presented into the test ear
- at all frequencies or preferably at 2 and 4k Hz
sisi instruction and procedure
- instruction: ask the pt if they can hear the increments
- training: steady tone at 20dB SL + 5dB increments every 5 seconds (begin with several big increments easily heard by patients
- start the test with 1dB increment
- present at 20dB SL if hearing loss is greater than or equal to 60dB Hl
- present at 75 dB HL (high level sisi test) if the hearing loss is less than 60dB HL
- -to avoid questionable scores (25-65%)
- count # of increments heard and find the %
sisi test results
- normal, conductive, and retrocochlear:
- negative to low sisi score=0-20%
- SNHL: cochlear site-of-lesion–depends on frequency
- positive/high sisi scores >/= 70% at high frequencies (2-4KHz)
- -1KHz: questionable scores of 40-60%
- -0.25 and 0.5KHz: low scores of 0-20%
- SNHL: retrocochlear site of lesion
- negative to low sisi scores: 0-20%
- **questionable/inconclusiive: sisi score of 25-65%
age and sisi tests
elderly perform poorer on sisi test
what to do if you suspect a cochlear loss
- sisi at 2 and 4KHz
- AR decay at 0.5 and 1Hz
- *sisi test and AR decay are complementary
patient attention and sisi test (variation of test in improve attention)
important to avoid false negatives
- cochlear HL: respond to the majority of increments
- to avoid false positives, randomly reduce to increment to 0dB
- retrocochlear HL: respond to few increments
- -to avoid false negatives, randomly increase the increment to 4 dB
sisi test and number of increments variation
- use 10 increments
- -if the pt hears 90% or more then you know you have cochlear
- -if the pt hears 10% or less then you have a low score which is neutral
- ten continue to 20 increments if the pt hears greater than 10% and less than 90%
sisi procedural variation: increment size
1 dB increment is the method of choice, but 0.75db increment is better
sisi test specificity and sensitivity
- cochlear (specificity) about 85%
* eighth nerve (sensitivity) about 65%
bekesy audiometry basics and what is allows for
by george von bekesy
automatic audiometry
industrial and military hearing screenings
pt controls the level of the tone
allows for: threshold assessment and site of lesion testing because of auditory adaptation
bekesy to measure auditory adaptation
there are two modes of pure tone presentation, interrupted (I) and continuous (c)
- there are also two tracing modes, sweep frequency trackings from low to high or reverse and fixed frequency plotting at each frequency
- ***adaptation should only occur for c not i
how to read a bekesy printout
a sawtooth graph
- downward sweep= period of inaudibility
- upward sweep= period of audibility
- midpoint= correlated well with behavioral threshold
- —threshold is calculated as the midpoint of the tracing between audible and inaudible
range of frequencies measured in bekesy
100-10000Hz
bekesy type I tracing
sweep frequencies are characterized by an overlapping of I and C tracings with a tracing width of about 10dB
*found with normal, CHL, and SNHL of unknown etiology
bekesy type II tracing
the C tracing falls below the I, generally at or above 1000Hz (not more than 20dB)
*usually seen in SNHL with cochlear origin. It is strictly a cochlear pattern
bekesy type III tracing
dramatic drop of the C below the I with a separation of 40-50dB or higher
* Consistent with retrocochlear pathology
bekesy type IV tracing
C dropping below the I at frequencies lower than 1000Hz as opposed to the type II
*could be cochlear or retrocochlear
bekesy type V
I is poorer than C tracing
- for at least 2 octaves
- minimum of 10dB separation (76% of cases?)
- is nonorganic (malingering) because subject has own standard for loudness for the continuous tone (40% of cases)
what are the two bekesy modifications to improve the accuracy of diagnostic results?
- reverse (Forward-backward) bekesy tracing
* bekesy comfortable loudness technique
reverse bekesy modification procedure
separates cochlear from retrocochlear disorders
- step 1) conventional bekesy (forward: low to high frequency)
- 1st is c tracing, then I tracing
- step 2) do the C tracing again, but this time in reverse (high to low frequency)
interpreting reverse bekesy tracings
compare the two tracings
- if there is an overlap/little difference between the 2= normal
- if there is greater separation and the reverse C tracing is poorer than the forward c tracing at mid to high frequencies shows retrocochlear (VIII tumor for example)
bekesy comfortable loudness modification
same conventional bekesy tracing except search for the comfortable loudness
- press the button when the signal is just uncomfortable loud and release it when the signal is just less than comfortable loud
- **do this with masking noise in the nontest ear
bekesy comfortable loudness rationale
retrocochlear disorders initially appear at suprathreshold level
*recording above the threshold would therefore be more sensitive to retrocochlear disorders
bekesy comfortable loudness patterns
there are three patterns Negaative patterns: *N1: overlapped *N2: c tracing is above I *N3: c tracing is below I **no retrocochlear lesion for N1-N3 (normal hearing or cochlear HL)
positive patterns:
- P1: C tracing falls far below I at high frequency
- P2: C falls far below I at low and or middle frequencies
- P3: forward-backward discrepancy
- c is normal in forward but abnormal in backward
- *these are all retrocochlear and the adaptation often happens to the c tone
Bekesy comfortable loudness limitations
not all ears could be classified as negative or positive
*19% of retrocochlear cases and 8% or the other ears did not fit into the six categories
brief tone audiometry via bekesy audiometry
(temporal integration intensity-duration relationship)
*measuring/comparing thresholds for (I) tones at 2 durations:
1= very short durations (20 msec)
2= longer durations (200msec)
**determine how much of a threshold change is needed to offset duration difference from 20 to 200 msec
interpreting brief tone audiometry via bekesy
- normal hearing: need an intensity change of 10dB to compensate for the effect of a 10-times change in duration (20 to 200 msec)
- cochlear cases: need a smaller than normal intensity change to offset a 10-times change in duration; temporal integration function is shallower than normal
limitation of brief tone audiometry via bekesy audiometry
not sensitive to retrocochlear lesions
*there is too much overlap between the results for cochlear and retrocochlear disorders
site of lesion testing : binaural interaction (BI)
there are two tests, name them!
- sensitive to brainstem lesions
- tests are:
- binaural fusion (BF)
- masking level difference (MLD)
binaural fusion test procedure
the pt’s task is to integrate the two parts of the target stimulus=binaural fusion
- require info from both ears
- sensitive to brainstem lesions
- uses 2 channel audiometer to present low pass segment of a word to one ear and the high pass segment of the same word to the other ear
- the test is scored by calculating the % correct
- poor performance= brainstem disorders
binaural integration masking level difference (MLD)
CAP test battery
- a test of lower brainstem integrity and release from masking
- interactions at the level of the SOC
- present 2 stimuli binaurally (or monaurally)
- signal (S) is 500Hz tone or speech
- Noise (N)
- compare noise/ masking levels in the 2 conditions measure while the noise or signal is:
- -homophasic (in phase) and
- -antiphasic (out of phase)
- calculate the dB difference of the masking levels between these 2 conditions (in and out of phase)
MLD results
release from masking phenomenon: the tones become audible when S and N are out of phase (SpiNo or SoNpi)
- then the noise must be raised further to mask the tone again (end test at this dB level)
- **MLD is the difference between the noise level needed to mask the tone/speech for the out of phase condition and the in phase condition (SoNo)
- —the amount of dB that the noise must be raised to mask the tone again in the out of phase condition
MLD normal results
a release from masking
- normal MLD values (frequencies less than or equal to 500Hz:
- -SoNo/SpiNo=15dB
- -SoNo/SoNpi=13dB
- lesions or the rostral brianstem, subcortec and cortex dont affect MLD
MLD explanation
in-phase condition, both S and N (competing stimuli) originates from the same percetpual sources-hard to be perceptually separated
*out of phase condition S and N originate from different perceptual sources–listener is better able to perceptually separate the competing stimuli
MLD sensitivity
hit rate was 69% for 27 pts with different brainstem lesions
MLD maturation factor
the age at which the magnitude of the MLD reaches adult levels depends partly upon masker bandwidth
- -for wider BWs, children perform like adults by 5-6 years or age
- -for narrower BWs, adult-like performance is not reached until an older age
MLD abnormal results
any compromise in the brainstem would result in less release from masking (reduced MLD)
- limitations (confounding factors):
- -reduced MLD with:
- —history of OM
- —learning disability
- —peripheral HL (degree of HL affects the MLD and may contaminate your results)
word recognition testing- PI/PB function
basic definition
performance intensity (PI) function when phonectically balanced (PB) word lists are used
PBmax
the maximum score on the PI/PB function
plateau for PI/PB
PI function evens out when the intensity of presentation is raised above the PBmax level
- the score does not improve or decline if intensity is raised
- **shows normal PI/PB function
rollover for PI/PB
when a reduction of speech recognition scores occurs above where PBmax is obtained
- *rollover of PB function indicated abnormal
- –cochlear is rollover
- –retrocochlear is severe rollover (>0.41)
site of lesion tests protocol
1) conventional audiometry including SRT, WRS, tymps, ART
a) if all is normal, no further testing needed
b) if large discrepancy b/t ears, go on to further testing
c) if ART are absent or elevated above expected amount, go on to further testing
can the specific pathology of a retrocochlear pathology be identified?
no not even through the most advanced audiologic procedures
*the most effective way to approach the differential diagnosis of cochlear vs. retrocochlear pathologies is through a combination of behavioral, electrophysiologic, and radiographic methods
list of qualitative tests for pseudohypacusis (4)
1) audiogram/shadow curve
2) stenger/ modified stenger
3) acoustic immittance measurements
4) low level PI/PB
quantitative tests of pseudohypacusis
1) auditory evoked potentials
2) automatic audiometry and lombard test
3) swinging story test, low level PB word test
4) ascending/ descending methods
5) pulse count methods, yes/no test
other terms for pseudohypacusis
- nonorganic HL
- functional HL
- malingering
- false or exaggerated HL