Auditory Neuropathy Spectrum Disorder (ANSD)

Auditory Neuropathy Spectrum Disorder (ANSD) is a term used for a pattern of test results that show normal function of the outer sensory hair cells of the cochlear, but abnormal transmission at some point from the inner hair cells of the cochlear along the auditory nerve pathway to the auditory brainstem (1)

• has been estimated that ANSD may account for around 1 in 10 children with permanent childhood hearing impairment (PCHI) (2)

The term ‘auditory neuropathy’ was first used in 1996 when Starr et al (3) described 10 children and adults who presented with hearing impairment characterised by:

• Present otoacoustic emissions (OAEs) and cochlear microphonics (CM) tests, demonstrating normal outer hair cell function
• Absent or severely abnormal auditory brainstem response (ABR), demonstrating a disrupted auditory pathway

The condition was variably referred to as auditory dys-synchrony or de-synchrony, peri-synaptic audiopathy, auditory mismatch, neural hearing loss or persistent outer hair cell function, before ANSD was adopted by consensus in 2008. This term was considered to better reflect the fact that this is not a diagnosis with single aetiology, but a range of possible disorders and prognoses defined by a pattern of test results (1)

Early studies indicated that around 40% of cases of ANSD may have genetic cause (2)

Several gene variants have been associated, including those of the DFNB9 gene which codes for otoferlin protein involved in synaptic functioning at the inner cochlear hair cells.(1) Other possible causes may include neurodegenerative, metabolic and mitochondrial conditions, and structural conditions, such as hydrocephalus, tumours, auditory nerve or brainstem anomalies. (1) ANSD has also been associated with a number of risk factors:(1,2)

• Hyperbilirubinaemia (particularly extreme requiring exchange transfusion)
• Prematurity (particularly extreme <28 weeks’ gestation)
• Low birthweight
• Anoxia
• Respiratory distress
• Hypoxic ischaemic encephalopathy or intraventricular haemorrhage
• Receipt of artificial ventilation
• Ototoxic drugs

Reference:

• BSA. Recommended Procedure Assessment And Management of Auditory Neuropathy Spectrum Disorder (ANSD) in Young Infants [Online]. British Society of Audiology, 2019. Available from: https://www.thebsa.org.uk/resources/assessment-and-management-of-auditory-neuropathy-spectrum-disorder-ansd-in-young-infants/.
• Sininger YS, editor Identification of auditory neuropathy in infants and children. Seminars in Hearing; 2002: Copyright© 2002 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA