Auditory neuropathy/dys‐synchrony: Diagnosis and management

Abstract

Auditory brainstem responses (ABRs) and otoacoustic emissions (OAEs) are objective measures of auditory function, but are not hearing tests. Normal OAEs reflect normal cochlear outer hair cell function, and an ABR indicates a synchronous neural response. It is quite possible for a patient to have normal OAEs but absent or grossly abnormal ABR and a behavioral audiogram that is inconsistent with either test. These patients, who may constitute as much as 10% of the diagnosed deaf population, have auditory neuropathy/dys-synchrony (AN/AD). To diagnose AN/AD accurately, ABRs are obtained in response to condensation and rarefaction clicks to distinguish cochlear microphonics (CM) from neural responses. Appropriate management is confounded by variation among patients and changes in auditory function in some patients over time. Recommendations for management include visual language exposure through methods such as American Sign Language (ASL), Cued Speech, or baby signs, and closely following patients.

Extremely low birth weight infants are at high risk for auditory neuropathy

“…11 The diagnosis will be missed if these high-risk infants are screened by OAE alone. In addition, an initially normal OAE may become abnormal over time, 31 which will interfere with accurate and early identification. Thus, all infants from the NICU should be screened by automated ABR, and an abnormal result should prompt evaluation for AN before discharge.…”

Does parental experience of the diagnosis and intervention process differ for children with auditory neuropathy?

“…Diagnosing ANSD should be straightforward but determining the auditory capacity in the infant period however is more challenging as patients with ANSD vary greatly [5,15,17,18]. Clinical characteristics include pure tone thresholds ranging from normal to profound levels, disproportionately poor speech recognitions abilities for the degree of hearing loss, difficulty hearing in noise; and impaired temporal processing [2,5,19,20].…”

“…The term auditory neuropathy or auditory dys-synchrony is used to describe a form of hearing impairment in which cochlear outer hair cell function is evident, but afferent neural transmission is disordered [1,2,3]. The term 'auditory neuropathy spectrum disorder' (ANSD) was adopted more recently as a way of describing its heterogeneous and multifaceted nature [4].…”

“…Evidence supports multiple etiologies and multiple locations as the site of lesion in ANSD, ranging from the cochlear receptors or inner hair cells (IHC), to kernicteric deposits anywhere from the spiral ganglion fibres to the brainstem, to a paucity of myelinated fibres in the VIIIth nerve [2,3].…”

“…By clinical definition, patients with this disorder have normal otoacoustic emissions (OAE's) and/or cochlear microphonic (CM) potentials, but exhibit an absent or severely abnormal auditory brainstem response (ABR) beyond the expected for the degree of hearing loss [1,2,3,5,6]. Although the diagnosis is clear with an absent ABR, no clear guideline exists on what exactly defines an abnormal ABR in cases of ANSD but it includes abnormal wave morphology with ABR thresholds significantly elevated above the expected degree of hearing loss [6].…”