Audiology - Screening Flashcards
When did neonatal screening for UK babies begin?
2003
What was the norm before neonatal screening for UK babies?
Only at risk populations were targeted
What % of hearing impaired babies have no known risk factors?
30 - 40%
What is the main screening technique used for babies in the UK?
Otoacoustic Emissions Test (OAE)
What type of permanent hearing loss is usually seen at birth?
Sensori-neural (the cochlea is fully formed at birth)
What are some of the features of the Otoacoustic Emissions Test?
High sensitivity and specificity, non-invasive, objective, cost-effective
What are Otoacoustic Emissions?
Weak signals that reflect off the outer hair cells
How do Otoacoustic Emission Tests work?
The cochlea is stimulated by the incoming sound, there is incomplete energy absorption and the weak outer hair cell activity is recorded as sound in the ear canal
How do Otoacoustic Emission signals arrive in the ear canal?
Cochlea stimulated - Basal Membrane disturbances travel away from sensory cells to the basal end of the cochlea - middle ear structures start to vibrate - sound wave created in outer ear canal
How are Otoacoustic Emissions measured?
Using a sensitive microphone (portable probe) which is inserted in to the ear
What do healthy cochleae produce?
A highly reproducible spectral pattern unique to each ear
Are Otoacoustic Emission Tests dependent on the client being conscious?
No - babies can be tested while asleep
If the cochlea responds to the Otoacoustic Emissions, what will the graph look like?
It will have several peaks and troughs
If there is no response from the cochlea during testing, what is the next step?
Refer for diagnostic testing
What can obscure test results?
Background noise and middle ear problems (glue ear etc)
What cannot be detected by Otoacoustic Emissions?
Pathologies beyond the cochlea
What does AABR stand for?
Automated Auditory Brainstem Response
What type of test is AABR?
Objective
What does AABR record?
The response of the brain in response to sounds
What components does the auditory pathway contain?
The cochlea, the VIII nerve, the brainstem, the midbrain and the cortex
What is measured in AABR?
Auditory Evoked Potentials (electrical charges produced in the auditory neural pathway)
What are Auditory Evoked Potentials often measured in response to?
Broad band clicks or tone bursts
What processes are involved in Automated Brainstem Response testing?
Audiometer generates stimuli, scalp electrodes detect tiny electrical signals, picked up by a monitor and recorded
How are AEPs measured?
Differential signals across pairs of electrodes
What are the names of the two electrodes used in AABR testing?
Active (positioned over area of high response activity) and Reference (positioned over area of low response activity)
What 3 areas of the auditory pathway are AEPs measured from?
Brainstem, midbrain, cortex
How are AEPs described?
In terms of their latency (time of response following stimuli)
What is meant by an early response to an AEP?
When a response occurs 0 to 10ms after stimulation
Where do early responses originate from?
The cochlea, the auditory nerve and the brainstem
What is meant by a middle response to an AEP?
When a response occurs 10 to 60ms after stimulation
What is meant by a late response to an AEP?
When a response occurs 60 to 500ms after stimulation
How long after birth should a child be AABR tested?
12 - 18 hours and retested 24 hours later if failed
What are the stimuli for AABR tests?
Clicks or tone bursts in decreasing intensity steps
At what intervals do the stimuli for AABR tests occur?
20 to 40 times a second
What are the most important peaks in response to AABR tests?
Peaks I, III and V
What does a clear response at 20 dBHL indicate?
Normal hearing
What is Behaviour Observation Audiometry?
Checklist for parents re newborns behaviour (responses to sounds etc)
Name a behavioural technique for screening young babies
Health Visitor Distraction Test
What does the Health Visitor Distraction Test involve?
Recording child’s responses to certain stimuli (rattle, ss, humming)
What kind of responses are health visitors looking for in the Health Visitor Distraction Test?
Head turns, eye turns, stilling, increased activity
What are some of the possible problems with the Health Visitors Distraction Test?
Not following procedures, visual or tactile cueing, rhythmic presentation of stimuli
