The complexity of ANSD starts at the time of
assessment
ANHS Conference May 2017
Florencia Montes, Monica Wilkinson, Carolyn Cottier
Outline
• ANSD review of definition
• OAEs vs CM
• Our data: hearing results, Risk factors, MRI results
• Understanding MRI terminology
• Case studies
• Summary waveforms abnormalities
• Take home message
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ANSD Review of definition
ANSD is characterised by absent or “severely abnormal ABR” with normal cochlear
outer hair cell function (OAE and/or CM).
Review of definition "severely abnormal waveform
morphology"
UNHS UK Protocol Guidelines for the Assessment and Management of Auditory
Neuropathy Spectrum Disorder in Young Infants, 2012:
There is some lack of consensus about the definition of “severely abnormal ABR
morphology”. They suggest Sininger’s definition:
“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
ANSD have a poor ABR proceeded by a large inverting CM that can last up to 5 or 6
ms”.
Review of definition: "severely abnormal waveform
morphology"
Ontario Infant Hearing Program Protocol: Auditory Neuropathy Spectrum Disorder
(ANSD) Sub-Protocol, 2016
ABR is absent or at least significantly depressed and/or delayed. No clear ABR
complex with a wave V latency between 5 and 10 ms
“Between normal and absent ABR lies a spectrum of ABR abnormality within which
differential diagnosis of an ANSD component can be very difficult”
ANSD is a label for a pattern of test results, it is not a diagnosis
Review of definition: OAEs vs CM
OAE responses and CM responses are not the same
OAE: OHC responses
CM: OHC+IHC. Click CM may be generated by IHCs even if the OHCs are extensively
damaged
CM may be present in normal ears, SN losses with reasonable low-mid frequencies,
or ANSD
Our data: hearing results
HEARING LOSS
Total babies assessed (as 3rd of May): 3021
• Normal 1452 (48.06%)
• CHL 620 (20.52%)
• SNHL 681 (22.54%)
• ANSD 118 (3.9 %) 14.7% of SN
• Mixed 97 (3.21%)
• Other no results (DNA, incomplete, passed away) 53 (1.7 %)
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Our data ANSD/retrocochlear (N=118):DP-OAEs
Unilateral ANSD: 60 cases
Bilateral ANSD: 58 cases
DP-OAES
In the Bilateral ANSD group, 64% present/partial, 29% absent, 7% not tested (flat
tymps)
In the unilateral ANSD group: 35% present/ partial, 57% absent, 8% DNT
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Our ANSD/retrocochlear data (N=118): Risk factors
RISK FACTORS
• No risk factors 64 (54 %)
• Risk Factors 54 (46 %).
• Of the risk factors, prematurity and VLBW (birth weight < 1500gm ) accounts
for 60 %
• Other risk factors hydrocephalus, family history, jaundice
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ANSD Risk factors: from the Literature
• Perinatal risk factors
• Extremely premature birth (<28 weeks gestation)
• Anoxia
• History of mechanical ventilation/ hypoxia or both
• Hyperbilirubinaemia
• Low birth weight (<2.5kg)
• Congenital brain abnormalities
• Genetics or family history of ANSD
• Associated with viral diseases, seizure disorders and high fever
• Accompanying neurological disorders including Friedrich ataxia, Charcot-MarieTooth syndrome (peripheral neuropathies)
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Imaging procedure at SCH
• Before 3 months of age: feed and wrap, no sedation or anaesthetic required
• After 3 months of age: general anaesthetic required for MRI
• Mostly offering MRI rather than CT scan
• Radiation risks
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ANSD: MRI findings (52 of the 118 patients had an MRI scan)
• Bilateral ANSD
• absent/hypoplastic nerves: 24%
• Normal nerves:76%
• Unilateral ANSD
• absent/hypoplastic nerves : 85%
• Normal nerves: 15%
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ANSD: MRI findings (from the Literature)
Systematic Review (Kachniarz et al, 2015)
• 4 studies (n=268 patients) evaluated findings on MRI in ANSD patients
• Diagnostic yield for ANSD ranged from 34-100%
• Cochlear nerve aplasia/hypoplasia ranged from 9-57%
• Diagnostic yield for brain specific findings of 33%
Unilateral hearing loss :MRI or CT? (Tilea et al, 2010)
• 3078 children (seen between 1999-2009), 234 had unilateral hearing loss
• 61 % had CT alone, 17% MRI alone and 22% CT and MRI
• CT showed 26 cases (11%) had IAM stenosis, MRI confirmed aplasia/hypoplasia
of cochlear nerve in 10/26 and demonstrated 11 (4.7%) more
• Cochlear nerve aplasia/hypoplasia is nearly as common as labyrinthine
malformations and only assessed by MRI
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14 Case studies
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Case 1 AC 2 K (Mark)
Bilateral refer
Type A tymps
No risk factors
Present DPOAEs
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Case 1 0.5kHz waveforms (Mark)
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Case 1 Clicks (Mark)
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Case 1 (Mark)
• Textbook ANSD
• Absent ABR bilaterally with clear Click CM
• Present emissions
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Case 2 ABR waveforms (Larry)
Direct refer.
Type A tymps
Hydrocephalus with Rickham reservoir
Present DPOAEs
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Case 2 ABR waveforms (Larry)
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Case 2 Click ABR waveforms (Larry)
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Case 2 3rd ABR Tb waveforms (Larry) with Shunt
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Case 2 3rd ABR (with shunt) Click waveforms (Larry)
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Case 2 (Larry)
Larry had 3 ABRs, after first ABR shunt inserted (at the time of first ABR Rickhan
reservoir). RE remains ANSD type, LE has improved in waveforms morphology to
normal.
RE ANSD
LE abnormal improved to normal
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Case 3 waveforms Test 1 (Roger)
Inconsistent refer.
Type A tymps,
No risk factors
Present DPOAEs bilaterally
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Case 3 Tb waveforms Test 3 (Roger)
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Case 3 Click waveforms Test 3 (Roger)
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Case 3 (Roger)
Initial ABR abnormal waveforms with present emissions BUT present Acoustic reflex
ABR gradually improved in morphology and thresholds to normal
We are monitoring with VROA soon
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Case 4 2 K waveforms (Mina)
Bilateral refer.
Type A tymps,
No risk factors
absent DPOAEs
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Case 4 0.5kHz waveforms (Mina)
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Case 4 Click waveforms (Mina)
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Case 4 (Mina)
Abnormal waveforms
Click -CM with possible wave V
MRI: Bilateral LVAS
SN
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Case 5 waveforms (David)
Bilateral refer
Normal tymps, absent DPOAEs
No risk factors
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Case 5 Click waveforms (David)
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Case 5 Click waveforms (David)
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Case 5 (David)
Abnormal waveforms. Click +CM with possible wave V RE (8ms), +CM LE with no
wave V
?ANSD, ?SN
MRI: Bilateral LVAS
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Case 6 Tb AC waveforms (Sarah)
LE refer
No risk factors
LE normal tymps absent OAEs
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Case 6 Click waveforms (Sarah)
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Case 6 ASSR (Sarah)
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Case 6 (Sarah)
Abnormal Tb- ABR with very small Click CM. ? Profound SN or ANSD
LE ANSD pattern, based on ASSR thresholds at least in the severe range (stopped)
No MRI
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Case 7 2, 4. 0.5kHz (Mary)
Bilateral refer
Normal tymps
31/40 weeks gestation. IVH (Brain bleed)
Present DPOAEs bilaterally
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Case 7 Click waveforms (Mary)
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Case 7 ASSR(Mary)
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Case 7 (Mary)
Bilateral ANSD pattern
? peaks with Tb- ABR RE only at a 100 dB nHL for 2 K, at expected latency (8ms) BUT
morphology is unusual. Presence of OAEs and Click showing +CM with no wave V
makes diagnosis of ANSD most likely
ASSR at moderate levels or better
MRI showed good auditory nerve and cochlear structures bilaterally. Presence of
blood around the nerve, ? No long term impact, unlikely the cause of the hearing
loss
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Case 8 Tb waveforms 1st ABR (Harry)
Inconsistent screening result
Type A tymps,
No risk factors
Present DPOAEs bilaterally
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Case 8 Click waveforms 1st ABR (Harry)
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Case 8 Tb waveforms 2nd ABR (Harry)
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Case 8 Click waveforms 2nd ABR (Harry)
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Case 8 Tb waveforms 3rd ABR GA (Harry)
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Case 8 Click waveforms 3rd ABR GA (Harry)
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Case 8 (Harry)
➢ 1st Assessment: Click ABR showed no CM and possible wave III and V in the RE
and possible wave V LE. But abnormal Tb- ABR, with present DPOAEs
➢ 2nd Assessment: LE +CM with abnormal ABR, RE +CM with possible wave III and V
➢ Repeat BERA under GA showed clear CM and absent ABR
➢ Bilateral ANSD
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Case 9 2&4K AC (Sam)
RE refer
LE all normal
RE normal tymps
Jaundice, family history unilateral loss
absent RE DPOAEs
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Case 9 1 K AC waveforms(Sam)
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Case 9 Click waveforms (Sam)
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Case 9 (Sam)
RE ANSD pattern
Tb peaks at high intensity unlikely to be wave V due to no change in latency with
decreasing intensity. ?too short latency (6ms for 2 and 4 K)
Click +CM with no clear wave V
MRI: Cochlear nerve absent
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Case 10 AC 2 K (Trent)
LE refer
Absent DPOAEs
No risk factors
RE normal
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Case 10 1K AC (Trent)
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Case 10 Click (Trent)
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Case 10 ASSR(Trent)
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Case 10 (Trent)
Click wave V larger than CM and of normal latency and morphology
Tb -ABR abnormal waveforms
LE ASSR thresholds in the mild to moderate range
MRI: Absent/hypoplastic LE cochlear nerve
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Case 11 2kHz & 0.5kHz (Jerry)
RE refer
RE normal tymps
No risk factors
Absent OAEs
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Case 11 Click (Jerry)
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Case 11(Jerry)
RE ANSD pattern
Repeatable peaks with Tb at 100 dB may cause confusion (?wave V)
But ? wave V would be too short for neonate.
Click showed +CM with no wave V
MRI: Right cochlear nerve absent
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Case 12 2, 0.5 & 4kHz (Eli)
Bilateral refer.
RE Type A, LE type B,
No risk factors
absent DPOAEs both ears
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Case 12 1KHz (Eli)
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Case 12 Click (Eli)
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Case 12 ASSR (Eli)
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Case 12 (Eli)
RE severe SNHL
LE ANSD pattern.
LE Questionable CM but Type B tymp. First assessment Type A tymps with clear CM
ASSR RE similar thresholds to ABR. LE in the profound to severe range
?ABR latencies too short for a neonate, ?mainly 0.5K and 1 K (<9ms)
MRI showed absent LE cochlear nerve, RE nerve difficult to visualise
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Case 13 4, 2, 0.5kHz (Isla)
LE refer.
RE all normal
No risk factors
LE Type B
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Case 13 (Isla)
LE moderate mixed hearing loss. Type B
Click not done as ANSD not suspected
Tb latencies too short again??
LE cochlear nerve not seen
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Case 14 0.5, 4kHz (Anna)
RE refer
No risk factors
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Case 14 2kHz (Anna)
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Case 14 Click waveforms (Anna)
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Case 14 (Anna)
Moderate RE unilateral hearing loss. Click was not done as ANSD was not suspected
(thresholds in the moderate range RE, normal LE))
Not doing well with speech and language development.
Had MRI showing bilateral absent/hypoplastic nerves. GA BERA at age 4 to rule out
ANSD/retrocochlear
Click –CM with clear waves III and V
No ANSD pattern but latencies RE much shorter than LE
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Cochlear nerve deficiency with ABR responses
We had 6 cases of CND and ABR responses in the mild to severe range
Most cases of CND have reported ABR as absent
One study reported 7 cases (out of 28) with unilateral CND and Click ABR ranging
from moderate to severe. Polarity of the click stimulus not specified. CND deficiency
defined by CT cochlear canal aperture measure
It is important to do imaging in patient’s with hearing loss regardless of auditory
threshold
“Cochlear Nerve Deficiency and Associated Clinical Features in Patients with Bilateral and Unilateral Hearing Loss”, Atsuko et al,
2013. Otology and Neurotology
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Summary of waveform results in ANSD cases
 Absent ABR
 Abnormal but not absent:
• Poor suprathreshold growth in amplitude over a large intensity range
• Poor reproducibility
• Small and or late wave V above 75 dB
• Unusual or inconsistent response morphology
• Abnormal latency
Take home message
•
ANSD is not always a straight forward diagnosis.
•
Peaks occur but be sure to assess morphology, replicability, amplitude growth and latency.
•
If only doing ASSR for threshold estimation, check for CM regardless of degree of the hearing loss
•
The value of ASSR with ANSD is still to be determined. ? Useful in differential diagnosis
•
Use Click when waveforms are abnormal, regardless of thresholds
•
Use Click when thresholds are above 70 dB nHL
•
Repeat assessment at some stage to rule out maturation/improvement (Eg hydrocephalus and hypoxia)
•
One should stress to families that ANSD is a pattern of results and not a diagnosis
•
If unilateral ANSD the possibility of cochlear nerve deficiency is high
•
Regular waveform reviews Improves quality of testing, learning opportunity,. May also help to have an
external person to review complex cases.
Thanks!
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ANSD Sub-Protocol
Test AC 2 and 0.5 K
If the response is absent or “abnormal”,
high intensity Click (90 dB nHL) with separate polarities, rate 39.1 p/s, to check for
CM
Procedure:
• 2 Condensation averages. Add C
• 2 Rarefaction averages. Add R
• 1 condensation tube off/clamped
• 1 rarefaction tube off/clamped
• Butterfly plot
ANSD Sub-Protocol continuation
Click High intensity with a rate of 88.1 p/s
to examine CM region in more detail, wave V may be degraded
Procedure:
• 2 Condensation averages. Add C
• 2 Rarefaction averages. Add R
• 1 condensation tube off/clamped
• 1 rarefaction tube off/clamped
• Butterfly plot
Waveform manipulation
C+R summed: attenuates CM activity and enhances neural activity
C-R subtraction: enhances CM and attenuates neural activity
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ANSD Outcome categories (Ontario Program)
DEFINITE ANSD component: present DPOAEs (2,3,4K) and Click ABR V-V’<0.1uV
PROBABLE ANSD component: present DPOAEs and Click ABR V-V’ 0.1uV-0.2uV
If DPOAEs absent or unreliable, apply table below:
CM, pk-pk,
uV
Click ABR
V-V’ pk-pk,
uV
<0.1
0.1-0.2
>0.2
<0.1
NS
NS
NS
0.1-0.2
probable
See ratio
NS
Ratio: calculate the amplitude ratio CM/ABR using peak-to-peak values. If >1.5 “probable ANSD’,
>0.2
definite
probable
See ratio
otherwise ‘not suspected’
CT and MRI scans: the Risks
CT scan risks
• Radiation risks include brain malignancy may arise in 1 in 4000 brain CTs (BMJ
2013), one excess case of leukaemia per 10 000 head CTs (Lancet 2012), risk of
thyroid cancer after temporal bone CT is 8 per 1,000,000 (European Radiology
2007)
MRI scan risks
• Related to need for sedation
• 1 in 400 sedations experience stridor, laryngospasm or apnoea and 1 in 200
require airway ventilation; approx 1% of sedated parent develop serious
complications requiring resuscitation
• Following CI, MRI not useful due to implant associated image distortion
(additional procedure required to address internal magnet)
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