Scottish Sensory Centre

Working with children with Cytomegalovirus, Auditory Neuropath Spectrum Disorders or Autistic Spectrum disorders

Presented on Monday 2 November 2009

Auditory Neuropathy Spectrum Disorder

With thanks: Kaukab Rajput GOSH, Glynnis Parker SCH, Alex Wheeler The Ear Foundation

Overview

• What is Auditory Neuropathy Spectrum Disorder?
  How is it diagnosed?
  How does it impact on a child?
  
• Can a CI aid ANSD?
  Research outcomes
• What do we need to consider when working with a child with ANSD?

The auditory pathway
Illustration from the CIBA Collection of Medical Illustrations, Volume 1

"Auditory neuropathy" Sininger, Starr et al (1995)

A hearing disorder presenting with grossly abnormal or absent neural responses, as measured by evoked potentials, in the presence of normal outer hair cell function evidenced by present otoacoustic emissions or cochlear microphonics.

What is ANSD?

Electrophysiological diagnosis characterised by:

• Presence of Evoked Oto Acoustic Emissions
• Absent or abnormal ABR with Cochlear microphonics present
• Absent stapedial reflexes
• Variable behavioural responses

Starr et al (1996), Berlin CI, Morlet T, Hood LJ (2003)

Auditory brainstem response

Records electrical activity generated by auditory nerve and brainstem pathways in response to a sound stimulus, using skin electrodes.

By signal averaging of approx 2,000 'runs', a trace emerges with peaks corresponding to centres of high activity in the passage of the signal along the auditory pathway.

Otoacoustic emissions (OAE)

OAE is actively generated by motility of the outer hair cells in response to an incoming stimulus.

Significance of OAE

• Requires normal external, middle and inner ear function - up to outer hair cells.
• Not recordable when average threshold >20-30dB
• Indicates satisfactory peripheral auditory function.

Cochlear microphonic

• Potentials generated mainly by OHC, possible minor component from IHC
• More robust than OAE in presence of middle ear problems
• More robust to minor cochlear insults.

Electrocochleography (EcochG) & Electrical ABR (EABR) in diagnosis of Auditory Neuropathy (case study)

Further findings

PTA thresholds	Normal to profound hearing loss, can be asymmetric, any configuration, variable
Speech recognition in quiet	Variable: mild to severe problems
Speech in noise	poor
OAEs	Normal initially but may disappear later
OAE suppression	absent
Cochlear microphonics	Present (inverts when stimulus polarity is reversed - Berlin et al 1998)
Stapedial reflexes	absent

Pathology

• Inner hair cell dysfunction
• Synapse dysfunction
• VIIIth nerve - true auditory neuropathy
• Brainstem abnormalities

AN/AD encompasses a range of conditions which differ in site and pathology - Cone-Wesson & Rance, 2000, Starr  et al, 2000)

1. Absent or malfunctioning inner hair cells

Genetic: OTOF mutation

2. Dysfunction of the synapse between the IHC and VIII N (transmitter problem)

3. VIII nerve – true auditory neuropathy*

* "Auditory Neuropathy" is a pathologic process involving the VIII cranial Nerve

True neuropathy involving the VIII nerve

• Cochlear nucleus
• Higher (2nd order) auditory pathway

Early waveforms can be normal

Gardner-Berry, Gibson, Sanli. The Hearing Journal 2005

Hearing Loss category	ECochG	acABR	EABR
Sensory loss	Mild to prof thresholds No APP	Present/normal for mild to moderately severe losses	Present/normal for severe to profound losses
IHC/ Synapse	APP at one or more frequencies	Absent/Abnormal waveform	Normal
True Auditory Neuropathy	APP at one or more frequencies	Absent/Abnormal waveform	Delayed Wave V
Brainstem Auditory Neuropathy	APP at one or more frequencies	Absent/Abnormal waveform	Early waves present but wave V delayed /absent

Associated features

• Sensorineural pattern of hearing loss - often low frequency (Sininger)
• Fluctuating hearing thresholds
• Absent acoustic reflexes
• Loss of discrimination, particularly at low frequencies
• Abnormal spread of masking
• Particular difficulties with speech-in-noise
• Poor temporal processing / Poor gap detection
• Poor localisation - reduced ability to detect interaural timing difference
• Dys-synchronous neural responses

From: Perceptual consequences of disrupted auditory nerve activity, Zeng FG, Kong YY, Michalewski HJ, Starr A, J Neurophysiology 93:2005

AD as a part of generalized neuropathy

Reported in

• Hereditary Motor & Sensory neuropathies [ie Charcot Marie Tooth, CMT]
• Friedreich's ataxia [FA]
• X linked inheritance - AUNX1
• Diabetes mellitus

CMT-Mutation of PMP22 gene which is essential for myelin formation - Schwann cell location - dominant inheritance.

Unilateral auditory neuropathy ...

• Ngo, 2006 : study of AD/AN in a newborn hearing screening program, Singapore.
• 9/52 children with hearing loss had AD/AN [6 bilateral and 3 unilateral]
• Unilateral ones had no perinatal 'risk factors', one had Moebius, one had absent 8th nerve
• Isolated case reports: incidental detection on school screening, one following mumps.

Delayed visual and auditory maturation in AN/AD

Aldosari et al (2003)

• ABR no response to 90dBnHL clicks at birth
• Normal OAEs
• No visual fixation
• At 9 months ABR - normal

Medical Conditions that can cause AN/AD

Perinatal causes - Madden et al (2002) 22 patients studied

• Hyperbilirubinaemia 50%
• Prematurity 45%
• Ototoxic drugs 41%
• (Family history 36%)
• Neonatal ventilator dependency 36%
• Cerebral palsy 8%

Cochlear Implants and ANSD

1. Research overview
2. Outcomes
3. Management

1. Overview of evidence

• AN Children do benefit from CI (Shallop et al 2001)
• AN v SNHL Children with CI (Peterson et al 2003)
• AN v AD, Gardner-Berry Gibson & Sanli, 2005
• CI v HA, Rance et al 2008 Prediction of CI outcomes, Walton, 2008

Peterson Summary

• No difference in programme requirements
• Functional benefit (MAIS) the same
• Both groups largely in oral educational programmes
• Recommend cochlear implantation as a viable option ... But ... CARE and careful evaluation.

Buchman et al, 2006

• MRI should be carried out for AN children:
• 9 (18%) of 51 children had cochlear nerve deficiency
• Children with AN and thin nerves may benefit from cochlear implantation
• Case Study

Walton et al, 2008

Predictive factors for CI+AN

• Medical co morbidities
• Cognitive abilities
• Cochlear nerve deficiency
• Cochlea anomalies

Rance et al 2008

• CI offers the possibility of significant open-set perception for children who show only limited discrimination ability to acoustic input.
• Some AN/AD children can do well with conventional amplification.
• How do we differentiate these children?

Notes: These authors raise some important management questions relating to children with AN/AD-type hearing loss. Some (particularly young) AN/AD patients who can do well with conventional amplification, therefore not appropriate to consider every child with this form of hearing loss as a suitable cochlear implant candidate Determining the level at which an AN/AD subject might reasonably expect a better perceptual outcome with a cochlear implant will require greater experience and subject numbers. The results of this study do suggest that this level may be different for subjects with AN/AD than that used for SN candidates.

Gardner-Berry, Gibson & Sanli, 2005

• Sensory hearing loss; good outcomes with CI
• Auditory Dys synchrony(AD); good outcomes predicted with CI
• Auditory Neuropathy (AN); less optimal outcomes predicted with CI
• Brainstem Auditory Neuropathy (BAN); less optimal outcomes predicted with CI.

Notes: SNL AD believed to be primarily cochlear pathology; good outcomes predicted with CI AN consistent with auditory nerve pathology. Less optimal outcomes predicted with CI BAN Consistent with auditory brainstem pathology. Less optimal outcomes predicted with CI.

References

Buchman CA, Roush PA et al (2006). Auditory Neuropathy Characteristics in Children with cochlear Nerve Deficiencies. Ear & Hearing 27 (4); 399-408

Rance G & Barker E. (2008). Speech Perception in Children With Auditory Neuropathy/Dys synchrony Managed With Either Hearing Aids or Cochlear Implants. Otology & Neurotology, 29:179-182

Gardner-Berry K, Gibson W, Sanli H (2005). Pre-operative Testing of Patients with neuropathy or dys-synchrony. Emerging Trends in Cochlear Implants. The Hearing Journal. 58 (11):24-31

Peterson A, Shallop J et al (2003). Outcomes of Cochlear Implantation in Children with Auditory Neuropathy. Jnl of Am Academy of Audiology, 14(4):188-201

Shallop JK, Peterson A, Fabry LB, Driscoll LW (2001). Cochlear Implants in Five cases of Auditory Neuropathy:Post-operative findings and progress. The Laryngoscope 111; 555-562

Walton J, Gibson WPR, Sanli H, Prelog K, (2008). Predicting Cochlear Implant Outcomes in Children with Auditory Neuropathy. Otology and Neurotology.29; 302-309

What are we dealing with?

• Look carefully at what is known about the type of ANSD
• Cochlea/ Cochlear nerve deficiency
• EABR results
• Do not assume progress consistent with 'standard' SNHL + CI

Habilitation support ...

• Consider temporal processing difficulties
• Use of Cued Speech?
• Sign - does it get in the way of developing spoken language?
• Monitoring Development of listening skills; Speech production

Management Summary:

• Be aware of emerging additional difficulties
• Quiet listening conditions
• Structured listening
• Visual support FM with CI when appropriate
• bilateral implantation

Where next

• Working with children with Cytomegalovirus