My Experience in Uncovering Hidden Hearing Loss
By Madeleine Salisbury
For many Disabled people, receiving a diagnosis is about more than medical administration, it’s a crucial part of one’s identity. “Being diagnosed gives permission to be ill. What was previously a complaint is now a disease.” A diagnosis becomes a key to belonging, community, and finding one’s people. A diagnosis turns a long explanation into a few words.
I had been on quite a streak of diagnosis collection as I worked my way through a lifetime of not-quite-rights. I had been bathing in the luxury of knowing that something was wrong after all, that my symptoms weren’t just imagined, and that my medical history had more to show than ‘chronic whinger.’ That was, at least, until I decided that my increasingly noticeable hearing problems were to be my next mission. I could hear conversations in a quiet room but wouldn’t hear my name being called in a noisy schoolyard. I could listen to music with headphones on but couldn’t tell what was being said on TV. Back in primary school, my teachers were concerned that I wasn’t listening, but I simply wasn’t hearing. Around the same time, I was disappointed that my parents would no longer sing me a bedtime song, but they were. I’d been riddled with middle ear infections that would leave me unable to hear at all for a week. My hypothesising brain decided that must count for something.
General practitioner, audiologist, ENT, audiologist, the same ENT, a different audiologist, on and on. My multiple audiograms (the results of being shut in a cupboard and pressing a gear stick when I heard a tone) showed a mild hearing loss in my left ear. So, at least I probably wasn’t faking it, but where was it all coming from? I hosted many sightseeing tours of my outer and middle ear, had an MRI, and had a grommet inserted in my ear drum at the ripe old age of 19.
Nothing to be found.
My determined and ever humorous ENT was reassuring. My validation-seeking brain wasn’t thrilled.
The next audiologist visit brought a new experiment, a speech-in-noise test. I was asked to identify sentences that I heard as the background noise was gradually increased. I was far worse at this than any regular hearing person should have been. This was a vital piece of my hearing puzzle; it just hadn’t found its place yet.
So where was I at that point? Hearing problems that became far more noticeable with background noise, that put me on an even playing field with my elderly customers at my grocery store job, that made conversations a guessing game. I remained apprehensive of social outings at restaurants and parties, knowing I wouldn’t be able to follow conversations. Subtitles remained on. Still without any physiological explanation, I was medically exhausted and crestfallen, still unable to truly believe I wasn’t imagining a condition that didn’t exist. Yet, I was managing and making adjustments for myself, as I did with my other conditions. I put my hearing difficulties up to comorbidities and gave up the chase for an answer.
As a budding neuroscience major with abnormal hearing, I thought it would be my little joke to take Auditory Neuroscience as a subject.
Suddenly, my hearing puzzle had snapped together.
Hidden Hearing Loss (HHL) is a synaptopathy, a disorder of “disruptions in synaptic structure and function” in which the connections between neurons—the brain cells—malfunction. It gets its name from being undetectable using standard clinical diagnostic methods, and it remains difficult to study in humans. Despite producing normal audiograms that appear to leave no reason for concern, people who experience HHL often have difficulty understanding and interpreting speech and complex sounds, particularly in the presence of background noise. This presentation is similar to that of an auditory processing disorder, a term that I had found suitable to identify with throughout my hearing mystery saga. My experience with the speech-in-noise test was more validating than I thought.
If one was to open up the eardrum of each ear like a door and move through, they would find the three ossicles. These tiny bones are the smallest in the body and form a chain that vibrates with the eardrum as a sound wave hits it. At the other end of this chain is the oval window. If this thin membrane also was a door, opening it would place a visitor in the cochlea, the little snail shell shaped organ that’s filled with fluid. Throughout the cochlea are tiny hairs, the stereocilia, that move when the fluid does. It is the movement of the stereocilia that allow them to turn sound waves into electrical signals for the brain to process. The loss and/or damage of the inner and outer stereocilia, often as a result of noise exposure, is often to blame for hearing loss and therefore forms the basis for common hearing tests. However, the synaptic nature of HHL means that it can occur in the absence of hair cell damage and remain enshrouded during clinical testing. Further contributing to this problem is that audiogram hearing tests are often performed in silent, noise proof booths, whereas as HHL often only emerges when background noise is present.
Like more readily diagnosable hearing loss, synaptopathies can be caused by overexposure to loud noise. Besides this, research has shown that old age, disorders of brain structure and function, and drugs that are toxic to the structures of the ear may increase the risk of developing HHL.
A contradiction that often begs for explanation is that my hearing is impaired, yet I have always experienced the sensory sensitivities that often come with neurodivergence. The presence of overlapping sounds fills me with discomfort, and the sounds of chewing and wrappers crinkling is near painful. Avoiding loud noise like the plague makes me fairly certain that it can’t be to blame for the state of my hearing. In fact, the opposite may be true. Hyperacusis refers to the perception of sound as being excessively loud and uncomfortable, more so than what would be experienced by the average person. Results of a 2016 study found that rats with noise induced synaptopathic damage became overly sensitive to further noise in the future, as measured by their startle response. Perhaps the presence of HHL in humans can produce sensory sensitivities in a similar way. Considering the complexity of the brain and auditory system, strange should-be-contradictions must be expected.
As I approach the end of this tale of lost and hidden things, can I say that Hidden Hearing Loss is the diagnosis for me? Is it my next key to belonging, to validation, to freedom from self-explanation? Perhaps this would-be answer would be clear if I was a rat in a lab. For now, I will look forward to seeing this mystery condition be wrestled into the spotlight and find solace knowing that some diagnoses simply like to remain hidden.
