AUDIOLOGIC ASSESSMENT

Ozarks Technical Community College

HIS 125

You can’t fit a hearing aid until you can perform/interpret audiograms!

Being able to perform an accurate hearing test and interpret the obtained results are imperative to:Making appropriate recommendations

○ Is a medical referral required?○ Amplification options○ Hearing aids versus cochlear implant?

Fitting hearing aids appropriately!

Basic Hearing Evaluation Audiogram

Puretone audiometry○ Air-conduction (AC) and bone-conduction (BC) testing

Speech audiometry○ Speech reception threshold (SRT)

This may also be called speech recognition threshold

○ Word recognition score (WRS) This may also be called speech discrimination score

The goal is to determine○ How well you hear○ How clearly you hear speech○ If there is a medical reason for hearing loss○ If there is a need for some sort of intervention

Hearing Loss is defined by… Type of Loss

ConductiveSensorineural Mixed

Degree of LossNormal, mild, moderate, moderately-severe,

severe, profound Configuration of Loss

Flat, sloping, rising, etc.

Puretone Audiometry Recall that human ears have an audible

bandwidth (frequency range) of 20 to 20,000 Hz

In audiometric testing, the stimuli are puretones from 250 to 8000 Hz. Why?

○ because human speech falls within these frequenciesMost commonly octave bands at 250, 500, 1000,

2000, 4000, and 8000 Hz are testedThe interoctave frequencies of 3000 and 6000 Hz

are also commonly tested in adults

Puretone Audiometry Air-conduction testing

Performed with headphones or insert earphones

Takes into account the entire auditory pathway ○ Outer ear, middle ear, inner ear, nerve, brain

Bone-conduction testingPerformed with a bone-conduction oscillator

placed on either mastoid bone (most common) or the forehead

Directly stimulates the inner ear and nerve○ Bypasses the outer and middle ear

Puretone Audiometry Threshold is the softest sound that a listener can

hear 50% of the time A bracketing technique is used to establish

threshold. Remember…down 10, up 5.If the patient responds, reduce the stimulus intensity by

10 dB. If no response, increase intensity using 5 dB steps. Repeat this procedure until you find threshold.

I prefer to start testing at 1000 Hz at 50 dB HL. I always use a pulsed puretone, as it is preferred

for patient’s with tinnitus.

Normal Hearing Normal AC and BC

thresholds Many different

scales exist regarding degree of HL

For the purposes of this class, we will use the scale on the next slide.

Degree of Hearing Loss This is the exact scale that

I use in interpreting audiograms Some clinics are more liberal

and consider normal hearing to be any threshold up to 25 dBHL

In determining the degree of loss, the textbook approach would be to calculate the puretone average (PTA=average dB of AC thresholds at .5, 1, 2 kHz) and compare the PTA to the scale at right. From: Northern, J. Hearing Disorders (3rd ed)

Speech Audiometry Speech reception threshold (SRT)

The softest level (dB HL) at which a patient can accurately repeat spondees (two-syllable words; i.e. baseball, hotdog, birthday) 50% of the time○ Uses the same bracketing technique as puretone

testingSRT is primarily used as a reliability check

○ In comparing the SRT to the PTA, they should be within 10 dB of each other

○ If you have poor SRT-PTA agreement, then the reliability of your results should be considered to be questionable

Word recognition score (WRS)The percentage of phonetically-balanced,

monosyllabic words that a patient can accurately repeat

Presented at either MCL (most comfortable level) or MIL (most intelligible level)○ This is generally thought to be approximately 40 dB

above the SRTA pre-recorded list of 25 to 50 words should be

presented to each earEach word should be preceded by a carrier phrase:

○ “Say the word pick”○ “Say the word room”

Speech Audiometry

WRS in determining site-of-lesion Patient’s with normal hearing or conductive

hearing loss will perform normally on WR testing Patient’s with only high-frequency or a mild, flat

SNHL will also generally perform near-normal The more severe the SNHL, the poorer a patient

will perform on WR testing Neural losses result in poor performance

Asymmetrical WRS, especially in the presence of puretone asymmetries, should be considered a “red flag” for an acoustic neuroma

In patient’s with a retrocochlear lesion, roll-over may also be present on WR testing. This means that with increased presentation level, the patient’s performance will actually decrease (i.e. 56% at 85 dB decreasing to 12% at 95 dB).

Audiometric Interpretation

If a patient has a disorder of the outer and/or middle ear ONLY, then AC thresholds will be abnormal in the presence of normal BC thresholds

Air-bone gap = greater than or equal to 15dB difference between AC and BC

This is called a conductive hearing loss, as sound cannot properly conduct through the outer and/or middle ear to reach the normal-hearing cochlea

Some Causes of CHL

Anotia Microtia Atresia Outer ear infection Middle ear infection Otosclerosis Dislocation of the middle ear bones Cholesteatoma Ear wax!

Conductive Hearing Loss Normal BC thresholds Abnormal AC thresholds

An air-bone gap is present at .5, 1, 2, and 4 kHz

WRS should be nearly normal, as there is no damage to the cochlea/nerve

*Note: recall that dB SL refers to sensation level, which is the intensity that is added to threshold. When performing WRS, the presentation level should be at the most comfortable/intelligible level for the patient. This level is generally thought to be the SRT + 35-40 dB SL. So in the example at right, the WR testing was performed at 65 dB HL.

Image from: telemedicine.orbis.org

This patient has a mild CHL

Audiometric Interpretation

If a patient has a disorder of the inner ear and/or auditory nerve, then AC thresholds will be equal to BC thresholds (no air-bone gap) and both will be abnormal

This is called a sensorineural hearing loss

Some Causes of SNHL

Aging (presbycusis) Noise Exposure Genetics Acoustic Neuroma Meniere’s Disease Ototoxic Drugs

Sensorineural Hearing Loss

Abnormal AC and BC thresholds

No air-bone gap WRS will vary depending

on degree of loss and cochlear vs. neural damage

According to the PTA method of determining degree of HL, this patient has a slight SNHL.

However, due to the sloping configuration, I prefer to define the loss as a slight-sloping-to-severe SNHL. It is more accurate.

Image from: telemedicine.orbis.org

Puretone Audiometry Interpretation If a patient has a disorder of the inner

ear and/or auditory nerve AND an outer/middle ear disorder, then both AC thresholds and BC thresholds will be abnormal AND an air-bone gap will exist

This is called a mixed hearing loss Example: 75 yo, male with age-related

hearing loss and bilateral otitis media

Mixed Hearing Loss

Abnormal AC and BC thresholds

Air-bone gap present Expected WRS

based on BC thresholds

This patient has a mild to moderately-severe MHL. Image from: telemedicine.orbis.org

If any of the following conditions exist, a patient must be referred for a medical evaluation by a physician (preferably an ENT):Visible congenital or traumatic deformity of the ear.History of active drainage from the ear in the previous 90 days.History of sudden or rapidly progressive hearing loss within the

previous 90 days.Acute or chronic dizziness.Unilateral hearing loss of sudden or recent onset within the

previous 90 days.Audiometric air-bone gap equal to or greater than 15 decibels

at 500 Hz, 1,000 Hz, and 2,000 Hz.Visible evidence of significant cerumen accumulation or a

foreign body in the ear canal.Pain or discomfort in the ear.

Always keep these FDA Regulations in mind…