Auditory Neuropathy: Variation on 
a brand new theme.

Deltenre,D., Mansbach,A.L., 
Bozet,C., Barthelemy,P.,
Renglet,T., Lasky,R.,
Becker,T. and Hecox,K.E.
Evoked Potential Unit, Brugmann 
Hospital, Brussels, Belgium

Auditory Neuropathy is a new 
diagnostic label which is defined 
by absent or severely distorted 
ABR’s with preserved otoacoustic 
emissions and cochlear 
microphonics.  The utility of the 
concept of auditory neuropathy is 
as an indicator of a 
pathophysiological process 
impinging upon the Inner Hair 
Cell - Primary Afferent 
functional complex.  We report 
three cases with 
electrophysiological findings 
indicative of the 
pathophysiological mechanism 
implied in auditory neuropathy, 
but who are at variance with the 
initial description.  Two 
subjects with a history of 
neonatal hyperbilirubinaemia 
presented initial findings 
consistent with the definition of 
auditory neurophathy.  Several 
months after the initial 
diagnosis, they lost their 
otoacoustic emissions but 
retained their cochlear 
microphonics.  One of them 
definitely benefited from 
moderate (+20 dB) hearing aid 
amplification. These two 
observations, coupled with the 
accumulating findings of subjects 
without ABR and otoacoustic 
emissions but showing residual 
microphonics and various levels 
of functional hearing suggest 
that auditory neurophathy can be 
one of several concurrent 
physiopathological contributors t 
some hearing losses.  A third 
case presenting in the context of 
a familial hearing deficit had 
elevated (80 dB) ABR thresholds 
that matched his behavioral 
thresholds although he retained 
click-evoked and distortion 
product otoacoustic emissions.   
This latter case suggests that 
the pathological mechanism 
responsible for the auditory 
neuropathy pattern could be 
restricted to primary afferents 
with low or intermediate 
thresholds.