audiogram interpretation
TRANSCRIPT
Audiogram InterpretationOzarks Technical Community College
Hearing Loss is defined by…Degree/Magnitude of Loss
Normal, slight, mild, moderate, moderately-severe, severe, profound
Type of LossConductiveSensorineural Mixed
Configuration of LossFlat, rising, sloping, precipitous
Normal HearingNormal AC and
BC thresholds (≤15 dB)
Many different scales exist regarding degree of hearing loss
For the purposes of this class, we will use the scale on the next slide.
Degree of Hearing LossThis is the exact scale that I
use in interpreting audiogramsSome 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)
Audiometric InterpretationIf 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 (CHL), as sound cannot properly conduct through the outer and/or middle ear to reach the normal-hearing cochlea
Some Causes of CHLAnotiaMicrotiaAtresiaOuter ear infectionMiddle ear infectionOtosclerosisDislocation of the middle ear bonesCholesteatomaEar wax!
Conductive Hearing LossNormal BC
thresholdsAbnormal AC
thresholdsAn 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
Image from: telemedicine.orbis.org
This patient has a mild CHL
Collapsing CanalsIf you ever discover a conductive hearing loss
component in the high frequencies when you are using traditional headphones, it is necessary to retest your air-conduction thresholds using inserts.
The pressure of traditional headphones can actually cause a collapse of the ear canal in some patients (especially true in the elderly)
Audiometric InterpretationIf 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 (SNHL)
Some Causes of SNHLAging (presbycusis)Noise ExposureGeneticsAcoustic NeuromaMeniere’s DiseaseOtotoxic Drugs
Sensorineural Hearing LossAbnormal AC and BC
thresholdsNo air-bone gapWRS 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, it is more accurate to define the loss as a slight-sloping-to-severe SNHL.
Image from: telemedicine.orbis.org
Puretone Audiometry InterpretationIf 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 (MHL)Example: 75 yo, male with age-related
hearing loss and bilateral otitis media
Mixed Hearing LossAbnormal AC and BC
thresholdsAir-bone gap presentExpected WRS based
on BC thresholdsThis patient has a
mild to moderately-severe MHL.
Image from: telemedicine.orbis.org
Configuration of HLFlat
Thresholds within 20dB of each other across all frequencies
RisingLow frequency thresholds are at least 20dB poorer
than high frequenciesSloping
High frequency thresholds are at least 20dB poorer than low frequencies
PrecipitousHigh frequency thresholds worsen by at least 20dB
per octave
Always keep these FDA Regulations in mind…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.