Audiogram interpretation

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<ul><li> 1. Ozarks Technical Community College </li></ul> <p> 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. 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. 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. 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. Some Causes of CHL Anotia Microtia Atresia Outer ear infection Middle ear infection Otosclerosis Dislocation of the middle ear bones Cholesteatoma Ear wax! 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: This patient has a mild CHL 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. 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. Some Causes of SNHL Aging (presbycusis) Noise Exposure Genetics Acoustic Neuroma Menieres Disease Ototoxic Drugs 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: 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. 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: 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. 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. </p>