“Hello? Can you hear me?”
We all know how difficult it is to hear the other person during a call with terrible cell service; everything sounds muffled, the audio keeps cutting out, and you feel as though you’re underwater. For individuals with auditory neuropathy spectrum disorder (ANSD), this is an everyday reality.
ANSD is an auditory condition in which the actual hair cells within the ear may work, but the auditory nerve that transmits asynchronous electrical signals from the ear to the brain doesn’t, resulting in hearing loss. Possible causes of ANSD include genetics, premature birth, hyperbilirubinemia (jaundice), and head trauma. Moreover, patients may present with mild to profound hearing loss. Due to this range of age, etiologies, and severity, ANSD is referred to as a spectrum. However, patients of all ages and severity show a common set of auditory symptoms; they struggle with differentiating sounds (temporal encoding) and understanding speech in noisy environments (speech discrimination). Sounds may fade in and out or be out of sync. Patients may appear to hear one day, but not the next.
Audiologists administer two tests to identify ANSD: otoacoustic emissions, which records responses from the cochlea, and auditory brainstem response, which examines the functionality of the auditory nerve. Since ANSD is associated with problems with neural transmission, otoacoustic emissions results are present, but auditory brainstem response results are flat or absent. If a child were to have ANSD, the first step towards diagnosis would be a failed hearing screening.
Administering auditory brainstem response testing to infants is vital in early identification of ANSD. Because the auditory system influences a child’s life early on, many newborns receive this screening 24 hours after birth. However, identifying the disorder from a diagnostic standpoint is difficult. “It’s a very tiny portion, maybe 3%, of our patient population,” highlights Christine Carter, an audiologist at Massachusetts Eye and Ear.
Without access to sound, speech and language development in infants are negatively impacted, which is why ANSD patients benefit from both hearing aids and cochlear implants. Many patients start off with hearing aids and see how this progresses. More information on ANSD has been uncovered in recent years, and cochlear implants have taken a stronger preference over hearing aids as patients get older, since they provide electrical stimulation directly to the auditory nerve.
ANSD is a rare but serious auditory condition that can severely impact an individual’s quality of life. Screening and amplification mechanisms allow for early identification and intervention, paving the way for improved hearing.
