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Audiogram interpretation

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Audiogram interpretation

  1. 1. Ozarks Technical Community College
  2. 2. Hearing Loss is defined by…  Degree/Magnitude of Loss  Normal, slight, mild, moderate, moderately-severe, severe, profound  Type of Loss  Conductive  Sensorineural  Mixed  Configuration of Loss  Flat, rising, sloping, precipitous
  3. 3. Normal Hearing  Normal 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.
  4. 4. 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)
  5. 5. 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 (CHL), as sound cannot properly conduct through the outer and/or middle ear to reach the normal-hearing cochlea
  6. 6. Some Causes of CHL  Anotia  Microtia  Atresia  Outer ear infection  Middle ear infection  Otosclerosis  Dislocation of the middle ear bones  Cholesteatoma  Ear wax!
  7. 7. 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 Image from: telemedicine.orbis.org This patient has a mild CHL
  8. 8. Collapsing Canals  If 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)
  9. 9. 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 (SNHL)
  10. 10. Some Causes of SNHL  Aging (presbycusis)  Noise Exposure  Genetics  Acoustic Neuroma  Meniere’s Disease  Ototoxic Drugs
  11. 11. 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, it is more accurate to define the loss as a slight- sloping-to-severe SNHL. Image from: telemedicine.orbis.org
  12. 12. 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 (MHL)  Example: 75 yo, male with age-related hearing loss and bilateral otitis media
  13. 13. 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
  14. 14. Configuration of HL  Flat  Thresholds within 20dB of each other across all frequencies  Rising  Low frequency thresholds are at least 20dB poorer than high frequencies  Sloping  High frequency thresholds are at least 20dB poorer than low frequencies  Precipitous  High frequency thresholds worsen by at least 20dB per octave
  15. 15. 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.

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