Auditory Neuropathy Auditory Dyssynchrony in newborns

1
Auditory Neuropathy /Auditory Dys-synchronyin
newborns

• Graham Sutton
• MRC Hearing Communication Group
• Manchester University

2
NHSP guidelines

• Assessment and Management of Auditory Neuropathy
  / Auditory Dys-synchrony.
• A Recommended Protocol
• 27 October 2004
• www.nhsp.info

3
Main Contributors

• Graham Sutton (Editor)
• Judy Gravel
• Linda Hood
• Guy Lightfoot
• Steve Mason
• Tony Sirimanna
• John Stevens
• Sally Wood

4
Results show

• ABR absent, or severely abnormal morphology at
  high levels
• but
• OAEs present and/or CM present
• What does it mean?
• What do we do?

5
Sininger (2002)

• The neural response (ABR) will be poor or
  completely absent but will occasionally show a
  small wave V response at high stimulus
  intensities.
• The majority of cases of AN/AD have a poor ABR
  preceded by a large inverting CM that can last up
  to 5 or 6 ms

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Slide from Berlin (2003)
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Terminology

• Auditory Neuropathy is a misnomer unless disorder
  of spiral ganglion cells and VIIIth nerve
• 'Auditory dys-synchrony'
• 'Neural hearing loss' proposed by Rapin Gravel
  as general term where not sensory, but the locus
  of pathology is unknown

8
Prevalence

• '1 in 10 of those with severely abnormal ABR'
• No good data on prevalence in deaf children

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Natural history

• May stay the same, worsen or improve.
• ABR may recover to be consistent with the
  behavioural threshold and with normal morphology
• If problem is due to maturation, recovery would
  normally be complete by 12-18 months. If not
  suspect another cause of AN/AD
• In some cases perceptual ability seems to improve
  although ABR remains abnormal.
• OAEs which are present at initial assessment may
  disappear, whether or not the child is aided

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Characteristics (1)

• Behavioural thresholds anywhere from normal to
  profound
• Poorer thresholds in the low frequencies
• Variable responses from test to test, but
  generally reliable within a single test
• Auropalpebral reflex may be absent regardless of
  the degree of hearing loss.

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Characteristics (2)

• Speech discrimination poorer than behavioural
  audiogram would suggest
• Hearing aids may be of less benefit than
  behavioural audiogram would suggest
• Greater difficulties hearing in competing noise
  than behavioural audiogram would suggest other
  features indicative of auditory processing
  difficulties.

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At initial assessment

• Click ABR absent
• could be due to
• hearing loss (SNHL or CHL)
• delayed maturation
• AN/AD

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Next steps in assessment

• Cochlear Microphonic (CM) response.
• OAEs
• plus if possible
• Stapedial reflexes tymp with 1000Hz probe tone

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Slide from Tony Sirimanna
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Interpretation

• If OAEs/CM absent then SNHL/CHL
• If OAEs/CM present then suspect AN/AD.
• or delayed maturation?

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Delayed maturation

• How to distinguish AN/AD from delayed maturation?
• No easy way
• Monitor
• Retest

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Risk Factors for AN/AD

• Hyperbilirubinaemia
• Anoxia
• Hypoxia/Prolonged assisted ventilation
• Extreme prematurity (lt28/40)
• Congenital brain anomalies
• Demyelinating conditions such as MS
• Syndromes associated with other peripheral
  neuropathies (Charcot-Marie-Tooth, Friedrichs
  Ataxia)
• Genetic factors
• Auditory Neuropathy has also been reported in
  cases where it is related to a viral infection or
  exacerbated by fever

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• ABR thresholds do not predict behavioural
  thresholds

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Management

• Information and support for the family
• Repeated audiological and communication
  assessment,
• Decisions about hearing aids or other
  intervention.

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Regular repeated assessments

• Behavioural thresholds in each ear determined by
  an age-appropriate method
• Electrophysiology - repeat ABR, CM and OAE
  recording at 8-10 weeks and 9-15 months.
• Tymp and reflexes.
• Assess development of communication

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Intervention?

• Hearing Aids
• FM system
• Cochlear implant
• Mode of communication
• Cued speech/ signing crucial
• Auditory-verbal therapy (AVT) is ineffective

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To aid or not to aid?

• Must wait until have some behavioural responses.
• Only aid if elevated behavioural thresholds
• Parents' wishes important
• Base aiding on behavioural responses
  observations, not on ABR
• Do aids help? - contentious
• Cortical ERA - P100 latency may help assess
  progress

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Cued Speech

• Invented 1966
• Dr R Orin Cornett (1913- 2002)
• "I really started with the conclusion that what
  was needed was a convenient way to represent
  spoken language accurately, through vision, in
  real time."

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Cued speech

• Emily's lipshape could bem, p or b.
• The handshape tells us that it is b.
• The hand position tells us that the following
  vowel will be either e (in egg), o (in on), or ue
  (in blue), all of which have different lipshapes

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• Mark's lipshape could be sh, ch, j or zh (as in
  treasure).
• The handshape tells us that it is sh.
• The hand position shows us that the following
  vowel will be either e (in egg) o (in on) or ue
  (in blue).

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Our past mistakes

• Look back at cases - now we know.
• Children who didn't progress with well-fitted
  aids and AVT
• Hearing loss that changed
• Results that were inconsistent
• we didnt check OAEs routinely in assessment of
  SNHL

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Key Messages

• Always test OAEs in assessment
• Learn how to measure CM
• Managing these children is difficult!
• Living with uncertainty
• We have a lot to learn
• Being open with parents and sharing information
• Take advice or refer to experts

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Further Information

• www.nhsp.info
• www.cuedspeech.co.uk
• www.kresgelab.org
• Seminars in Hearing 23, No 3
• Sininger YS, Starr A, (Eds). (2001) Singular.
• Berlin CI, Morlet T, Hood LJ (2003). Pediatr clin
  N Am, 331-340

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• Thank you!
• graham-sutton_at_supanet.com