Dhar chapter 4 Flashcards
occlusion effect
improvement of hearing sensitivity or increased loudness lateralized to the side of a blocked ear canal upon application of the bone vibrator to the skull. makes for better BC than usual (low freq)
the lateralization effect
independent of the site of application of the bone vibrator
bone vibrator placement
- mastoid; yields lower thresholds than forehead. forehead was about 10dB less overall.
- forehead; some argue this placement is better because of less variability of thresholds, less contribution of middel ear mechanism, and less impat of individual variables such as subcutaneous fat and hair that can confound findings on mastoid. some say forehead vibes front-to-back. disadvantages: reduced dynamic range and need for diff. calibration values.
sensorineural acuity level (SAL) test
requires a constant/relatively high level of masking noise presented through a BC vibratorthat is places on the forehead. Then, AC thresholds are obtained for eachear with the constant BC masking level. these masked AC threshold are then compared to unmasked AC thresholds to determine BC thresholds. eliminates need for contralateral masking, but is vulnerable to the occlusion effect. hard to do = not in standard practice
vibrator application force and surface area
the greater the spplication forces of the BC thresholds, the lower (more sensitive) the BC thresholds. amount of force hard to maintain.
larger the contact area = reduced variability in BC testing
The Weber Test
test conducted using a low freq. tuning fork (256 Hz). fork goes on forehead near
hairline. “which ear is hearing the tone?”.
if tone lateralizes, it will go to better hearing ear or the ear with the conductive loss. if its perceived at midline = normal hearing
test is not useful.
the Rinne test
use at 256Hz tuning fork. fork goes to mastoid and lateral w/o touching pinna. “indicate if you hear the tone”. if patient hears tone longer by AC, then Rinne test is positive (normal or sensorineural HL)
Negative test when handle is heard when on the mastoid meaning conductive HL
shows sensitivity of 84%
the Bing test
low freq. tuning fork. fork struck and stem goes on mastoid. cover the EAM and ask “tone louder when EAM covered?
positive when patient says tone is louder when ear occluded = normal or sensorineural
negative=patient notices no change. conductive.
test is not useful.
bone conduction vibrator
instead of transducer element driving the diaphragm to move air molecules, it is anchored and encased in a small box/shell attached to headband to make a vibe surface pressed against skull. contact area shouldn’t be more than 1.75cm. Radioear B-71 most commonly used.
bone conducting auditory brainstem response testing
ABR can be effected by magnitude, wave morphology, latency.
BC testing can help to rule out conductive impairment in ABR testing
Conductive loss
BC should be w/in normal limits, but difference between AC and BC thresholds should represent the magnitude of the conductive loss.
Carharts notch
otosclerosis is where this is normally found. it is an apparent sensorineural loss implied by reduction in BC sensitivity around 2000Hz
Large Vestibular Aqueduct Syndrome (LVA)
congenital disorder in which the vestibular queduct is larger than 1.5mm. hearing loss is normally sensorineural, however low freq. conductive loss found in 17%-38%.
3 explanations:
1. abnormal endolymphatic pressure adversely effecting cochlear mechanism.
2. stapes is fixated in the oval windows
3. incomplete development of the states
Superior Semi-circular canal dehiscense syndrom (SSCD)
low freq air-bone gaps with normal middle ear structures. balance problems triggered by middle ear pressure change or loud sound.
