Ms Florencia Montes1, Ms Kirsty Gardner-Berry2, Ms Carolyn Cottier1
1Sydney Children’s Hospital, Randwick, , , 2NextSense, ,
Background:
A diagnosis of ANSD has significant implications for management. The auditory brainstem response (ABR) typically shows absent/abnormal neural waveforms, which can be incorrectly interpreted as a profound hearing loss if ANSD is not carefully ruled out. Previous literature has suggested that ANSD is mostly a bilateral condition, with less than 10 % of cases involving one ear. However, a recent study reported a higher incidence of unilateral ANSD with cochlear nerve deficiency being the most common cause (Liddle et al, 2022).
Over a period of 20 years clinicians within our centre have noted atypical morphological features on ABR testing in cases of ANSD which had not previously been systematically characterized. This study was designed to investigate these features in more detail with the view to improving the accuracy of differentiating between a typical sensorineural hearing loss (SNHL) and ANSD, and reducing the chance of a missed diagnosis. The potential implications of missing the diagnosis of unilateral ANSD and cochlear nerve deficiency is referral for cochlear implantation with a greater risk of poor outcomes.
Method:
We retrospectively reviewed 20 years of audiological and MRI data of infants diagnosed with unilateral ANSD. Infants with present cochlear microphonics (CM) were separated into those with absent ABR waveforms versus those with atypical ABR morphology.
Results:
A total of 1330 infants were diagnosed with a permanent hearing loss. Of those with unilateral hearing loss (392), 29.3% had severe-profound SNHL and 27.3 % ANSD. Cochlear nerve deficiency was present in 89% of unilateral ANSD cases with MRI results.
Infants with atypical ABR morphology showed abnormally short latency peaks.
Conclusion:
Unilateral ANSD is as common as unilateral severe-profound SNHL and more common than bilateral ANSD. If the morphological characteristics of the ABR waveform are not carefully analysed the diagnosis of ANSD may be missed.
Biography:
Florencia Montes is a senior audiologists with expertise in electrophisiological assessment in infants.
Dr Kirsty Gardner-Berry BSc. M.Aud. MASA PhD OAM
Kirsty has been working as an audiologist for over 25 years, specializing in the use of electrophysiological testing techniques to assist in the management of infants and children with hearing loss. Kirsty has a particular interest in auditory neuropathy spectrum disorder (ANSD) and is a member of the Australasian Newborn Hearing Screening Committee.
Carolyn Cottier is a paediatrician, with expertise in hearing loss in infants.