Paediatric Hearing Assessment

Transcription

1 Information for parents Paediatric Hearing Assessment Hearing assessment of infants is limited by their ability to respond to sounds. This is determined by both the development of the hearing system and the general development of the child. Development of behavioural responses Neonate Reflexive responses e.g. eyeblink, startle. 3-4m Attempts to localise sounds, association between objects and sounds. Reflexive responses diminished. 4-5m Auditory-vocal feedback, experimentation with voice. 7m Good at localisation. Responses to sound in neonates and young infants Eyeblink (auropalpabrel reflex) Gross motor response Stilling Startle Eye movement/widening Crying Grimacing (Heart rate changes/breathing changes) Paediatric Hearing Assessment, April

2 Test methods 0-6 months of age Behavioural observation audiometry (BOA) Observation of responses to intense stimulus. Does not give indication of threshold. Can rule out severe and profound losses only. Reflexive response can be inhibited, particularly with repeated presentation of stimulus. Tests of preference to assess hearing for this age group are therefore objective tests months of age Distraction test Traditional test of choice. Forms the HV hearing test in some areas (no longer in Berkshire). Based on the ability of this age group to localise sounds at and close to ear level. Works on the fact that younger children need social reinforcement for responding to sounds. In practice difficult above 12m. Requires 2 testers. A distractor in front who controls the attention of the child, the test and assesses whether there has been a response A presenter behind the child presenting the sounds Tests hearing to a range of sounds frequency specific warble tones, high frequency rattle, voice. Lots of potential flaws and possibilities for missing child with hearing loss. Paediatric Hearing Assessment, April

3 6-30 months of age Visual Reinforcement Audiology (VRA) Visual Reinforcement Audiometry A conditioned response to sound (usually head turn) is reinforced by a visual reward. Conditioned by simultaneous presentation of sound and reinforcer (reward). Usually have a second tester controlling the attention of child not essential. Sounds typically presented from a loud speaker. Once child is reliably conditioned for the test, only then can go on and start testing the child s hearing. Assesses hearing across frequency range, typically 0.5kHz to 4kHz which are important for speech and language access. Present sound, child turns head, present re-inforcer once child has turned. Can also be presented using insert earphones or headphones to obtain ear specific information. Also can do bone conduction VRA (tests the underlying hearing - the cochlea, inner part of the ear). Variations on test. CORA conditioned operative reinforcement audiometry e.g. tactile reward, edible reward. Tests the hearing in the better hearing ear Paediatric Hearing Assessment, April

4 30-36 months of age Performance audiometry Can start trying at 24m (although limited success). Conditioned voluntary response to a stimulus (warble tone) presented in the sound field. E.g putting man in boat, peg in board when a sound is heard. Assess hearing typically at 0.5, 1 (or 2), and 4kHz. (all if have co-operation of child). Verbal comprehension not required child is conditioned by demonstration. 36+ months of age Play audiometry As for performance audiometry but with headphones. Obtain ear specific information across frequency range. Performance testing Usually only get information at 3 frequencies for each ear for younger end of age group. Test technique usually modified compared with adult version of test so that reliable results can be obtained in short a time as possible. Paediatric Hearing Assessment, April

5 5/7 years of age Pur etone audiometry Traditional adult test. Play Audiometry testing Same idea as play audiometry but child now old enough to press a button. Obtain more frequency specific information kHz. Often children have a PTA screen that does not test the hearing below a certain level e.g. 20dBHL. If responses at this level normal hearing. Speech discrimination tests Can be used to obtain additional information about how the child uses their hearing and listens. Can be used to get an indication of hearing thresholds if traditional threshold tests have failed. To support information already obtained about hearing thresholds e.g. for difficult to test children. McCormick Toy Test (18-36m). Live voice without lip reading. Automated. AB(S) wordlists. Lists of words that are phonemically balanced. Four Alternative Auditory Feature test (FAAF) (>7yrs) May be something that is used more in future. Paediatric Hearing Assessment, April

6 Objective Test Methods Otoacoustic emissions (OAEs) McCormick Toy Test Can be used for any age child provided are settled and quiet. Active processes in the outer hair cells of the cochlea. OAEs are the sounds produced by these active processes. OAEs are measured in the ear canal in response to a stimulus presented to the ear. What are OAE's? Low-intensity sound generated by the cochlea (inner part of the ear) and measured in the ear canal. First discovered in Return or release of acoustic energy from the cochlea. produced by active processes within the cochlea. presence of OAEs indicates mechanically active outer hair cells (OHCs). Do not provide a measure of threshold. Presence of OAEs rules out a greater than mild hearing loss (not frequency specific). Absence of OAEs indicates a hearing loss but no indication of the degree of hearing loss. OAEs can be absent if there is blockage in the ear canal or middle ear (e.g. glue ear). Paediatric Hearing Assessment, April

7 OAEs abolished for hearing loss > 25dBHL. Why are OAEs good for neonatal hearing screening? Non-invasive. Can be carried out on sleeping baby. Short test time. Good, easy to use equipment available. BUT Difficulties with small ear canals. Middle ear effusion, especially for intensive care babies. Electric response audiometry Different types of this technique that look at different aspects of the hearing system: Auditory Brainstem Response (ABR). Threshold ABR in children 0-4m. Diagnostic ABR. Need to be asleep and relaxed. Mainly used for threshold testing in adults. Need to be alert. Uses of ABR Objective measurement of hearing threshold. in babies (0-4m) for whom difficult to obtain behavioural information. young children who are difficult to test. older babies/young children can be tested but need to sleeping. Screening for hearing loss in neonates. Diagnostic test (adults). Measurement of the response of the auditory pathway from the cochlea up to the level of the brainstem. Clicks are presented which measure the hearing in the frequency range 2-4kHz (1-4kHz near threshold). Paediatric Hearing Assessment, April

8 Threshold ABR Ideally baby is asleep. Intensity of stimulus is reduced to find the minimum level at which the response is present to determine threshold. Results give the average hearing at threshold across the range 1-4kHz. Can also carry out bone conduction ABR to determine whether hearing loss is conductive, sensorineural or mixed. Variations are available to provide frequency specific information but not widely used. Screening ABR Clicks are presented at one intensity level only, typically 40dBnHL. Clear Response waveforms present and repeatable at screening level. No Clear Response - waveforms are absent at screening level. Those with hearing losses worse than a mild hearing loss will fail the hearing test. May not detect mild hearing losses. Auditory Steady State Responses (ASSR) Ideally baby is asleep. Similar set-up to ABR. Can obtain frequency specific information from both ears at the same time. Mainly used for more accurate first fitting of hearing aids to neonates. Paediatric Hearing Assessment, April

9 Tympanometry and Acoustic reflexes For assessing the middle ear and auditory nerves. Non-invasive and can be performed when child awake but need to be relatively still. A small probe is placed into the ear canal and the pressure is varied to move the eardrum and record a trace. Assists in diagnosis of middle ear effusion (congestion behind the eardrum) or glue ear. Presence or lack of acoustic reflexes can be a useful tool to assist in diagnostic procedures. Tympanometry For further information about the Trust, visit our website This document can be made available in other languages and formats upon request. Department of Audiology Telephone Fax audiology@royalberkshire.nhs.uk Website: AUD_958 Dept of Audiology, April 2014 Review due: April 2016 Paediatric Hearing Assessment, April