Aud clinical assessment exam Flashcards
What are some key considerations when taking case history?
- Sudden, gradual or fluctuating loss
- When was change first noticed
- Can you hear in a group situation?
- How often does the particular sensation occur?
- Does anything trigger the sensation?
- Describe the sound (for tinnitus)
- Is it continuous or intermittent
- Loss of balance? Describe the feeling
- On any medication?
- Medical history
- Family history of hearing loss?
- Was it congenital, acquired, hereditary, childhood, early adulthood etc.
- Occupation
- exposure to noise
- Any amplification devices currently
- Ability to hear speech
- Any disabilities
- If child, ask about birth history/postnatal days
- Developmental milestones being met?
- Speech delay?
- Family history of speech and lang delay?
- Learning or behavioural concerns?
- Childhood illness?
Which frequencies is PTA obtained for generally?
250, 500, 1000, 2000, 4000 and 8000 Hz
How do you calculate the Pure Tone Average?
Average threshold of 500 Hz, 1 kHz and 2 kHz
Define the degrees of hearing loss
< or equal to 25 = Normal, 26-40 = mild, 41 - 55 = Moderate, 56-70 = Moderately Severe, 71-90 = profound
What tone should be used as a starting tone for people with potentially normal hearing?
30 dB
If initial tone cannot be heard, what should the next tone be?
50 dB
If the 50 dB tone cannot be heard, what is the next step?
To increase in 10dB steps until a response is obtained
What is the Hughson Westlake Technique?
This is essentially a “Down 10 , Up 5 ” procedure– if a response is obtained, decrease the intensity of the tone by 10 dB; if a response is not obtained, increase the intensity by 5 dB
A threshold is the lowest hearing level at which responses occur in a series of ascending trials, with two out of three responses required at a single intensity level
How would you instruct a patient for PTA?
You will hear a series of tones (whistles). I want you to press this button for me every time you hear a tone. I want to find out the softest sound you can hear. So press the button even if the tone is very, very soft. Do you have any questions before we start?”
What are the key steps involved in PTA?
- Turn the audiometer on and allow 10 minutes for the audiometer to warm up.
- Perform a listening check of the audiometer (Why and how?)
- Perform otoscopic examination (If the patient has discharging ears, impacted wax, sore ears, or ear operation performed within 2 weeks, audiological assessment should not be performed).
- Seat the patient properly for testing (Why and how?).
- Instruct patient
- Place earphones properly. It is important that the centre of the earphone diaphragm is facing the concha (opening of the ear canal) on each side. Make sure that the red earphone is on the right ear.
- Test the better ear first.
- Present tones of 1-1.5 sec in duration. After the presentation of a tone, you should allow for at least 2-3 sec before you present the next tone. Vary the rhythm of your tone presentation (Why and how?)
- Test 1 kHz, then 2 kHz, 4 kHz and 8 kHz. Repeat at 1 kHz for a reliability check (difference in thresholds should normally differ by no more than 5 dB). Then test 500 Hz and 250 Hz.
- If there is a difference of 20 dB or more across the adjacent octave frequencies, you need to test at the half-octave frequency (e.g. 1.5 kHz, 3 kHz or 6 kHz) as well.(e.g., in ski-slope audiograms)
- Remember to give adequate positive reinforcement to the client. Try to look at the client rather than looking at the audiometer all the time.
What are five extrinsic factors that may impact on PTA threshold measurement?
Extrinsic variables –
• physical environment (background noise, lighting, temperature etc)
• Equipment (e.g., calibration, h/p worn out, broken electric wires, poor contact at joints)
• Test methodology (methods other than the Hughson-Westlake procedure – e.g., guessing)
• Instructions (inadequate or poorly phrased)
• Inadequate reinforcement during test
What are five intrinsic factors that may impact on PTA threshold measurement?
Intrinsic –
• neurophysiologic factors governing organic sensation
• internal noise linked with vascular, digestive and respiratory function
• listener’s motivation, intelligence, attention
• familiarity with the listening task
• listener’s understanding of test instruction (language barrier, misunderstanding etc.)
What are 5 limitations of PTA?
- Results affected by noise (physiologic and ambient noise) – giving raised thresholds
- It requires a behavioural response. Hence, young children and difficult-to-test patients may not respond reliably to auditory stimuli.
- A client can deliberately exaggerate a hearing loss (e.g., in compensation cases).
- Only test at octave frequencies. Abnormal hearing at other frequencies are not tested.
- It requires a specific environment to test accurately (e.g. Sound proof booth/quiet room)
- Relies on calibrated and quality equipment
What are four points relating to the test, re-test variability
• Threshold testing at any frequency varies from test to test.
• Variability is usually the smallest at 1 kHz, but greater at other frequencies.
• Variability is large at low frequencies (e.g., 0.25 kHz)
Reason: sound leaking through the gap between the skull and the earphones (and background noise getting in through the gap)(Kylin, 1960)
• Variability is large at high frequencies (e.g., 4 & 8 kHz)
Reason: standing waves are created which affect the intensity of the sound heard by the listener. A slight change in positioning of the headphone changes the intensity of sound (Hickling, 1966)
Are high or low/mid frequency sounds more affected by standing waves?
High
How regularly are audiometers calibrated?
Yearly
What are the three mechanisms of Bone Conduction?
- Inertial stimulation
- Compressional stimulation
- Osseotympanic stimulation
What is intertial stimulation?
- When the skull vibrates as a unit, the inertia of the ossicular chain causes it to lag behind.
- Relative movement between the footplate of the stapes and the oval window occurs. Thus, sound is transmitted into the cochlea as per air-conduction (AC) route.
- This mechanism is more important for low frequencies (e.g., 500 Hz).
What is Compressional stimulation?
- Occurs when forces are transferred from the skull into the cochlear fluid (perilymph).
- Causes movement of the membranes of the oval and round windows to different extents (different stiffness), and the cochlear aqueduct, resulting in deformation of the basilar membrane and hence stimulation of the cochlea.
- This mechanism makes a greater contribution to the transmission of high frequency sounds (e.g., 4 kHz).
What is Osseotympanic stimulation?
- Vibrations of the skull produce sound energy inside the ear canal. Part of the energy travels to the TM, middle ear and then the inner ear (via the regular air conduction route)[This energy transmission is known as osseotympanic stimulation.], while the remaining energy leaks out of the ear canal.
- The sound going through the TM into the middle ear and the inner ear is much reduced if there is a middle ear problem (conductive loss). Thus, osseotympanic stimulation does not work if a ME problem is present.
What instructions would you give for BC?
“You will hear the same tones as before. I want you to press this button for me every time you hear a tone. I want to find out the softest sound you can hear. So press the button even if the tone is very, very soft. Do you have any questions?”
Which frequencies are tested for BC?
500, 1000, 2000 and 4000 Hz
Which ear is tested first in AC?
Better ear
Which ear is tested first in BC?
Worse ear
What to do if reverse air bone gap found?
(1) re-test with careful attention to bone vibrator placement;
(2) check if test procedure (or instruction) is correct;
(3) check calibration of bone vibrator.
What are 7 factors affecting the validity of BC thresholds?
- Variation in the size of the skull and thickness of the skin and bone of the skull affect the BC thresholds.
- Maximum output of audiometer for BC is only 60-70 dB HL. So it can’t measure the AB gap correctly if the AC>70 dB.
- With sound delivered through the bone vibrator, the whole skull is vibrating. The cochlea with better sensitivity will respond to the sound. So, it’s not possible to know which cochlea is responding unless an appropriate masking procedure is applied.
- From a theoretical perspective, there is no energy loss for bone conducted sound to travel from one ear to the other. Hence, interaural attenuation for a bone conducted sound is taken as 0 dB {but it can vary from 0 – 10 dB in practice}.
- Vibrotactile responses (vibrations) may occur for 500 Hz at about 55 dB HL. So, vibrotactile responses, marked by VT on the audiogram, should not be considered as true hearing responses.
- Environmental noise affects the measurement of BC thresholds. Hence, BC thresholds are elevated when testing in non-sound treated rooms.
- When conducting BC testing at the low frequencies (500 & 1000 Hz) with one ear occluded, the measured BC threshold may be better than the true BC threshold by 5 to 15 dB. This is called an Occlusion Effect.
What is Carhart Notch?
Carhart (1950) found that patients with otosclerosis (in the early stages) often show a dip in BC thresholds around 2000 Hz. This is often called a “Carhart Notch”.
How can ME disorder make BC thresholds worse?
BC thresholds are influenced by middle ear disorders because both inertial and osseotympanic modes of stimulation depend on the function of the middle ear to various extents.
What are the three rules of masking?
- If the bone conduction threshold of the better ear and the air conduction threshold of the test ear differ by 15dB or more, bone masking required
- If the bone conduction threshold of the non test ear and the air conduction threshold of the test ear differ by 40dB or more, air masking is required
- If the air conduction threshold of the test ear and the air conduction threshold of the not test ear differ by 40dB or more, air masking is required
What are the steps for bone masking?
- Obtain and record the unmasked BC threshold with the bone vibrator on the mastoid of the test ear.
- Select an initial amount of masking (+10 dB) for the NT ear (i.e. nontest air-conduction threshold plus 10 dB EM). This masking noise is presented via the headphone (or insert) to the NT ear.
- Start at the unmasked threshold level of the test ear that you have previously established (as per Step 1) and present the tone through the bone vibrator to the test ear [Note: BC threshold will remain unchanged if the hearing loss is conductive; but BC threshold will change if hearing loss is sensory/neural.]
- Each time the client responds to the pure tone signal presented to the test ear, increase the masking noise presented to the non-test ear by 10 dB.
- Each time the client does not respond to the pure tone signal presented to the test ear, increase the signal in 5-dB steps until the client responds again.
[Kei (2015) called this : UP 10, UP 5 procedure for masking] - Continue the procedure until the masking noise can be increased over a 30 dB interval without producing a shift in the threshold level of the test ear (i.e. over a plateau of 30 dB). See Example 1 for details. [Some clinics use a plateau of 20 dB]
What are the instructions for air masking?
“This time I’ll put a rushing noise in your other ear. I want you to ignore this rushing noise and listen for the same tones as before. I want you to press this button every time you hear a tone. So press the button even if the tone is very, very soft. Do you have any questions?”
Why is the 30dB plateau used in masking?
(1) To safeguard errors due to calibration,
(2) To allow for patient’s variability in performance, and
(3) To allow for the occlusion effect when performing bone masking at low frequencies (i.e. 500 Hz and 1000 Hz).
What is Central Masking?
Central masking is a shift or worsening in
threshold of the test ear due to the introduction of masking noise in the nontest ear. This shift in threshold is mediated through the central nervous system.
• Thecentralmaskingshiftbeginstooccuratlow masking intensities and appears to increase slightly with increased masking (usually 5-10 dB; can be as high as 15 dB).
• Centralmaskingmay(ormaynot)occurduringthe masking procedure. Its occurrence is unpredictable.
How do you find the max masking level?
Mmax=BCt +IA
What is the masking dilemma?
Masking dilemma occurs when adequate masking cannot be achieved in the non-test ear without simultaneously producing overmasking.
• It occurs when the masking noise we put in already exceeds the maximum masking level (i.e., M > Mmax ), resulting in overmasking.
- occurs in bilateral conductive hearing loss
How do you calculate and individuals IA for air conduction?
Take the unmasked Air conduction for test ear and minus the AC/BC min of non test ear
Can you calculate the IA if the unmasked and masked AC threshold for the test ear are the same?
No, you can only estimate a range within which it might fall
What are the principles of tympanometry?
A sound (226 Hz pure tone at 85 dBSPL) is delivered to the ear when the pressure in the ear canal is varied from +200 daPa to 400 daPa. The sound reflected by the eardrum is measured and analysed.
What is Ear Canal Pressure?
The change in applied pressure inside the ear canal is measured with reference to the Atmospheric Pressure (e.g., how much greater or smaller than the Atm. Pressure). [Note: 1 daPa (decaPascal) = 10 Pascals]
What does 0daPa mean?
no difference in pressure between the ear canal pressure and Atm. pressure. When the air pressure inside the middle ear equals the pressure of the ear canal, the ear drum vibrates freely and a large portion of sound energy is transmitted into the middle ear system (