What is AN/AD?

Explaining Auditory Neuropathy/Dys-synchrony (AN/AD) is difficult, and I seem to define it differently each time someone asks. The simplistic version is that sound enters the inner ear normally, but as it reaches the brain it gets impaired/distorted. It's compared to listening to a radio station that is out of tune; sound comes in and out due to a fuzzy signal. The timing of the inner hair cells is not in sync, thus the auditory nerve is not properly stimulated for receiving a clear signal. People with AN/AD tend to have normal OAEs, but completely absent or abnormal ABRs (see Glossary). This is why Aubrey was diagnosed later; she had normal OAEs at birth and this is how she passed the newborn screening test. Her OAEs have since disappeared, which is very typical with AN/AD.

You will see different names for this disorder: Auditory Neuropathy (the original name), Auditory Neuropathy Spectrum Disorder (ANSD), and most recently Auditory Neuropathy/Auditory Dys-syncrony. This gives you a little glimpse into how confusing and messed up this disorder is. In the early years, it was believed that the auditory nerve was the primary culprit. The nerve was damaged or not present. More recently it's believed that about 70% of the cases actually have robust nerves, but the inner hair cells are not firing properly. This is where "Dys-syncrony" comes into play and when cochlear implants (CIs) became the treatment of choice. The cochlear implant bypasses the damaged inner hair cells to provide proper stimulation to the auditory nerve, thus providing a clear, consistent signal to the brain. Beautiful! However, some researchers believe that the nerve is always somewhat effected.

There are some people with AN/AD who do not have hearing loss and rather experience only the distortion. But, in most cases, people with AN/AD also have hearing loss. The thought is that the AN/AD causes the hearing loss. The degree of the hearing loss and AN/AD is across the board and quite unique for each individual. Hence, the other name of Auditory Neuropathy Spectrum Disorder.

We believe that Aubrey falls on the mild to moderate end of the spectrum. Her AN/AD is not so severe that all she hears is a "buzz" and it's not completely on the mild side, as we would expect better speech articulation and more progress with hearing aids and therapy. Her hearing loss level is moderate to moderately-severe in the high frequencies. This all means that Aubrey falls in the very hard to treat category. Her hearing loss and AN/AD is not in the profound range, therefore she was not automatically a candidate for a CI. Her condition is also not mild enough for being able to learn complex speech and language with hearing aids and therapy alone.

What causes AN/AD? There are several possibilities, but in some cases it just happens! There have been adults who have been diagnosed after years of typical hearing and nerve response. We do not know the cause of Aubrey's AN/AD. She has been examined, poked and prodded head to toe. We even went through genetics counseling and so far we have no known cause. Here is a list of causes:

• A freak of nature - it just happens
• Jaundice/high bilirubin levels at birth
• Premature birth
• Ototoxic medications 
• Genetic mutation (i.e., the Otoferlin gene mutation has been highlighted as a cause of AN/AD).

So, we are dealing with both hearing loss and AN/AD, which makes treatment and management very complex. I have included a few helpful links for better definitions and to hear simulations of what it sounds like to have AN/AD. Brace yourself. It took me a long time before I could listen. There are also cochlear implant simulations at the top of the page.

http://www.nidcd.nih.gov/health/hearing/neuropathy.asp

http://kidshealth.org/PageManager.jsp?dn=familydoctor&lic=44&cat_id=192&article_set=61053

http://www.audiologyawareness.com/hearinfo_neuropathy.asp

http://www.healthaffairs.uci.edu/hesp/Simulations/simulationsmain.htm