Audiology Review

Objectives: Describe ear-specific type, severity and

configuration of a hearing loss.List reasons a child would refer OAE

screening.Correlate ABR thresholds to audiogram.

Audiogram – Degrees of loss

Normal

Slight

Mild

Moderate

Moderately-Severe

Severe

Profound

Audiogram – Types of loss

Sensorineural:Bone conduction and air conduction thresholds abnormal and within 10 dB

Conductive:Bone conduction thresholds normal, >10 dB Air-Bone Gap

Mixed:Bone conduction thresholds abnormal, >10 dB Air-Bone Gap

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XO

Audiogram – Configuration of loss

Configurations Flat Sloping* Rising* Notched Cookie-bite Reverse cookie-bite

*Modifiers Gently (< 20 dB difference between octaves) Steeply (20-30 dB difference between octaves) Precipitously (> 30 dB difference between octaves)

Audiogram

Audiogram

Audiogram

Audiogram

Tympanogram

Type A: NormalPeak near atmospheric pressure

                              Type B: Abnormal

No peakNeeds medical attention

                Type C: Borderline normal

Negative pressureMonitor. May need medical attention

Otoacoustic emissions

Outer hair cell activity in cochlea adds energy to transduction process

OAE equipment elicits activity and records presence of additional energy

Absent OAEs

Present OAEs

Cutoffs

Absent when loss is greater than 40 dB HL(Norton 1993)

Pure tone thresholds most ideal

School age children should be screened at the following times: first entry into school every year, K-3rd grade 7th grade 11th grade upon entrance into special

education upon grade repetition upon entering a new

school system without evidence of having passed a previous hearing screening

Pure tone

screen

OAE screen

Sensitivity 87% 65%

Specificity 80% 91%

(Sabo et al 2000)

(ASHA)

ABR threshold

Click threshold approximates (±10 dB) pure tone threshold 2 – 4 kHz

Tone burst thresholds approximate pure tone threshold within 20 dB in 93% of children within 15 dB in 80% of children

(Stapells et al 1995)

Normal hearing

Bone and air conduction thresholds are normal (-10 – 15 dB HL)

Tympanogram type A (or C) Otoacoustic emissions are present Normal ABR threshold

Conductive hearing loss

Outer and/or middle ear disorder Bone conduction thresholds are

normal Air conduction thresholds are elevated Usually tympanogram type B

(sometimes C, rarely A in children) Otoacoustic emissions are absent ABR thresholds are elevated

Conductive pathologies

Otitis media OM w/effusion

can be asymptomatic

Bacterial OM gluey purulent

effusion greater CHL

Chronic OM can lead to

permanent hearing loss

damage to middle ear/TM

damage to basal hair cells via round window

Conductive pathologies

Otitis media Cholesteatoma

epithelial cyst erodes bone retracted TM may

create pocket for epithelial cells to collect

Conductive pathologies

Otitis media Cholesteatoma Occluded ear canal

cerumen foreign objects

Conductive pathologies

Otitis media Cholesteatoma Occluded ear canal Craniofacial

anomalies Atresia Ossicular

malformations

Sensorineural hearing loss

Inner ear or retrocochlear disorder Bone and air conduction thresholds

are elevated and similar Tympanogram type A (or C) Otoacoustic emissions are absent

(greater than mild losses) ABR thresholds are elevated

Sensorineural hearing loss

Congenital Maternal Infection Syndrome Mutation

Acquired Meningitis Ototoxicity Cochlear Insult

Mixed hearing loss

Outer and/or middle ear disorder AND Inner ear or retrocochlear disorder Bone conduction thresholds are

elevated and air conduction thresholds are elevated more

Tympanogram type B or C Otoacoustic emissions are absent ABR thresholds are elevated

Mixed hearing loss

Separate etiologies EVA + OME Maternal CMV + Cholesteatoma

Single underlying etiology CHARGE syndrome