Objectives • What is Auditory neuropathy? » » » »
Auditory Neuropathy in Children - an Otologist’s Perspective
Etiology & Pathogenesis Diagnosis of AN Evaluation of AN & SNHL Classification
• Management of ANSD » Conventional amplification » Cochlear implants
Oliver F. Adunka, MD Assistant Professor
• Cochlear Nerve Deficiency » Why important for AN? » Diagnosis, Evaluation, Management Based on a Presentation by Craig A. Buchman, MD
Auditory Neuropathy • Term ‘Auditory Neuropathy’ first used in 1996 • Described as: » ‘Abnormal auditory nerve function in the presence of normal cochlear receptor hair cell activity reflected by preserved otoacoustic emissions (OAEs) and/or cochlear microphonics (CMs)’ in 2003
What is Auditory Neuropathy?
• Not entirely new » Children w/ flat ABRs who respond to sound » Matured technology allows identification
• Inter-individual performance differences » Classic SNHL impairs frequency resolution » AN/AD timing of neural activity? » Disrupted perception based on temporal cues 1. 2.
Controversy Multiple aspects of ANSD • Terminology » Auditory neuropathy vs. Auditory dys-synchrony » Neural hearing loss? » Neural conduction disorder?
• Etiology • Pathomechanisms • Management
Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI. Auditory neuropathy. Brain 1996; 119:741-53. Starr A, Michalewski HJ, Zeng FG, Fukikawa-Brooks S, Linthicum F, Kim CS, Winnier D, Keats B. Pathology and physiology of auditory neuropathy with a novel mutation in the MPZ gene (Tyr 145->Ser). Brain 2003; 126:1604-19.
Basic Assumption Early approach @ UNC started in 2003:
AN/AD is a heterogeneous group of disorders with a similar electrophysiological profile •Several causes pp •Varietyy of clinical appearance » Different auditory perceptual abilities
•Necessitates individualized management •Expect variable outcomes Individualize the clinical protocol
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Rapin I, Gravel JS. Auditory neuropathy: a biologically inappropriate label unless acoustic nerve involvement in documented. J Am Acad Audiol 2006; 17:147-50.
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SNHL & ANSD @ UNC Interaction of Hearing Professionals
• Diagnose or confirm diagnosis » Single polarity click ABR, OAEs
• Imaging (MRI) » CNS & individual nerves
• Observation & amplification until VRA possible
• Behavioral testing g » Normal: close f/u, repeat ABR? » Abnormal: conventional amplification
• Intensive predominately auditory based therapy
• Absent or inadequate speech & language production/speech perception » Cochlear implantation?
Medical Assessment
Timeline Early Diagnostic Evaluation & Management of SNHL & ANSD
• Otologic examination • Imaging (MRI) • Referrals » Neurologic consultation » Genetics consultation » Ophthalmology O hth l l consultation lt ti
What we are looking for?
Possible Etiologies of ANSD
• Etiology
• Prematurity • Neonatal distress
» Hereditary or acquired
…Associations
• Associated problems » » » » »
» Hyperbilirubinemia » Perinatal asphyxia » Artificial ventilation
Seizures Motor delays Visual impairment Ear canal problems Otitis media
• Inner ear morphology • Cochlear nerve integrity
• Gentic abnormalities » OTOF, PMP22, MP2, NDRGI » Charcot-Marie-Tooth syndrome, Guillain-Barre syndrome
• Infectious processes MRI
» Viral infections (mumps, meningitis)
• Ototoxicity • Head injury 1. 2.
Range G. Auditory neuropathy/dys-synchrony and its perceptual consequences. Trends Amplif 2005; 9:1-43. Starr A, Michalewski HJ, Zeng FG, Fukikawa-Brooks S, Linthicum F, Kim CS, Winnier D, Keats B. Pathology and physiology of auditory neuropathy with a novel mutation in the MPZ gene (Tyr 145->Ser). Brain 2003; 126:1604-19.
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UNC ANSD Cohort Biographical Facts & Associations • Prospective study, 10 years
~72% Positive History
» Clinical characteristics of ANSD » Document benefits from assistive devices
• Infants & children, n>150 large number of very small children, just beginning to see outcomes
• Evaluation all ABRs performed at our institution
» Pediatric audiologist » Otologist
Management ANSD Bilateral (n=104) vs. Unilateral (n=26)
Bilateral ANSD
Management of ANSD
Unilateral ANSD
CI ECAP Recordings
Device/HA Utilization
(n=30)
No Assistive Device, n=18
Bilateral AN CI (n=45)
Bilateral AN HA (n=41)
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Why Cochlear Implants Work? …in many cases of ANSD • Maybe not always a neural HL? • Synchronization of neural response?
Cochlear Nerve Deficiency
Facts about CND
Cochlear Nerve Deficiency
• Small or absent CN
• Studies: IAC morphology (CT): diagnostic of cochlear nerve deficiency1
• What do we know? » Previously described in small IACs » Failed stimulation w/ CI » Contraindication to CI
1.
• TB Histology1: absent CN …with normal IAC & inner ear
• Recent studies: MRI can identify IAC nerves image absent CN directly2
Shelton C, Luxford WM, Tonokawa LL, Lo WW, House
WF. The narrow internal auditory canal in children: a contraindication to cochlear implants. Otolaryngol
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Head Neck Surg 1989;100:227-231.
2.
Jackler RK, Luxford WM, House WF. House detection
with the cochlear implant in five ears of four children with congenital malformations of the cochlea.
Nelson EG, Hinojosa R. Aplasia of the cochlear nerve: a temporal bone study. Otol Neurotol 2001;22:790-795.
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Laryngoscope 1987;97:15-7.
Glastonbury CM, Davidson HC, Harnsberger HR, Butler J, Kertesz TR, Shelton C. Imaging findings of cochlear nerve deficiency. AJNR Am J Neuroradiol 2002;23:635-643.
First Case
Change in Protocol
• Bilateral profound HL • CI right w/ no NRTs®, no benefit • CI left, normal NRTs®, 100% PBK @ 3 years
• MRI for children w/ SNHL started around 2002 @ UNC
• High resolution protocol Glastonbury et al1 protocol, CISS imaging
• ABR using single polarity stimuli • Behavioral data (VRA) ( )
1.
Glastonbury CM, Davidson HC, Harnsberger HR, Butler J, Kertesz TR, Shelton C. Imaging findings of cochlear
nerve deficiency. AJNR Am J Neuroradiol 2002;23:635-643.
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CND @ UNC
Patient Characteristics I
• • • •
• Audiological Profile1
>50 children with CND since 2002 ~90% ears absent CNs, ~10% small CNs ~½ bilateral CND ~½ unilateral CND
» » » »
w/ normal contralateral CN
• All but one failed NIHS
CM present in ~ 70% or ears Absent neural responses Profound or severe-to-profound SNHL Represents ~10-15% of ANSD population!!
• MRI Characteristics2 » ~60% of ears have normal IAC » ~40% of ears have normal labyrinth » many of them have hypoplastic malformations absent semicircular canals, small cochlea
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Buchman CA, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Grose JH. Auditory neuropathy characteristics in children with cochlear nerve deficiency. Ear Hear 2006; 27:399-408.
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Adunka OF, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Jewells V, Buchman CA. Internal auditory canal morphology in children with cochlear nerve deficiency. Otol Neurotol 2006; 27:793-801.
1.
3.
Adunka OF, Jewells V, Buchman CA. Value of computed tomography in the evaluatio of children with cochlear nerve deficiency. Otol Neurotol 2007; 28:597-604.
2.
Patient Characteristics II
Buchman CA, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Grose JH. Auditory neuropathy characteristics in
children with cochlear nerve deficiency. Ear Hear 2006; 27:399-408.
Adunka OF, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Jewells V, Buchman CA. Internal auditory canal morphology in children with cochlear nerve deficiency. Otol Neurotol 2006; 27:793-801.
Normal IACs Axial HRCT, MRI, parasagittal MRI
• CT Findings » 19 children CT & MRI » ~50% have normal IAC
» All w/ normal IAC have patent BCNC Normal BCNC no stimulation after CI,, absent CN,, normal CV anatomyy
•
CT completely normal! …in a subgroup of children
• and thus miss CND! Small BCNC partial bony obliteration, normal CV anatomy, absent CN 1.
Adunka OF, Jewells V, Buchman CA. Value of computed tomography in the evaluatio of children with cochlear nerve deficiency. Otol Neurotol 2007; 28:597-604.
Small IACs Axial HRCT, MRI, parasagittal MRI
1.
Adunka OF, Jewells V, Buchman CA. Value of computed tomography in the evaluatio of children with cochlear nerve deficiency. Otol Neurotol 2007; 28:597-604.
CND Conclusions • ~10-15% of AN ears ~70% have CM, absent distal waves
Small BCNC
• MRI primary imaging modality • Normal IAC: MRI identifies all cases • Small IAC: MRI identifies the small IAC » HRCT further defines status of CN ~ 70% or ears
single g nerve,, NR ABR,, normal facial fct.,, profound p HL
Absent BCNC - suggestive of absent CN » ~ 30% remain inconclusive
• HRCT for small IACs • For indeterminate ears: electrical ABR Absent BCNC single nerve, CM potential, profound HL
1.
Adunka OF, Jewells V, Buchman CA. Value of computed tomography in the evaluatio of children with cochlear nerve deficiency. Otol Neurotol 2007; 28:597-604.
1.
Buchman CA, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Grose JH. Auditory neuropathy characteristics in
children with cochlear nerve deficiency. Ear Hear 2006; 27:399-408.
2.
Adunka OF, Roush PA, Teagle HF, Brown CJ, Zdanski CJ, Jewells V, Buchman CA. Internal auditory canal morphology in children with cochlear nerve deficiency. Otol Neurotol 2006; 27:793-801.
3.
Adunka OF, Jewells V, Buchman CA. Value of computed tomography in the evaluatio of children with cochlear nerve deficiency. Otol Neurotol 2007; 28:597-604.
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Really deficient Nerve? …or can we just not see it on MRI?
• CI in 5 ears w/ CND » » » »
All had sound awareness None had ECAPs None gained open-set speech perception Very poor users
• Why sound awareness?
Single Nerve & Patent BCNC • Small IAC on MRI » Normal facial function » Patent BCNC (via CT scan) indicating possibility of some auditory nerve fibers
• Implantation or not?
» Non-auditory somato-sensory stimulation?
Conclusions I • ANSD heterogeneous group
Conclusions
» Multiple causes » Study population still very young » Many w/ multiple challenges
• Rarely normal hearing • Some benefit from: » Amplification » Cochlear implantation
• Some do not benefit from HA or CI
Conclusions II
Conclusions III
• Early involvement of otologist
• Select cases remain inconclusive
» …as part of the evaluation team!
• MRI instead of CT for screening SNHL including AN!
» Small IAC, single nerve, patent BCNC » Use everything you have when IAC is small » Electrical stimulation ABR for unclear ears!
• CND ~10-15% of AN ears! » ~70% electrophysiological p y g AN p pattern!!
• CT selectively » IAC < 3 mm, Single nerve in IAC, Cochlear obstruction » Semicircular canal malformation …to identify position of the facial nerve
» Temporal bone pathology
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Oliver F. Adunka, MD Assistant Professor Otology, Neurotology, Skull Base Surgery Department of Otolaryngology/Head and Neck Surgery
Office: (919) 966-3342 Pager: (919) 216-5886 eMail:
[email protected]
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