Question
I have a patient who is a neurologist and is suffering from unilateral hyperacusis; in fact he feels like he hears a distorted sound in his right ear when he is expossed to a relatively loud sound. Audiological tests are normal and he does not take any medication except high cholestrol pills and his general health is fine. Any suggestions?
Answer
I have had the opportunity to evaluate a few very similar cases in my 14 years as a dedicated tinnitus & hyperacusis specialist here in Portland, Oregon. I have suspected a defect in the sound-bearing system in these cases that causes it to go into an abnormal behavior at a certain decibel level or a certain pitch component. In my speculation, I have decided it is most like a set of tires on a car that appear just fine when driving at a slow or moderate speed, but which go into a vibratory spasm at a higher rate. The most likely source of this auditory system defect is in the air filled middle ear space with its very precisely tuned ossicular chain. Even the tiniest of misalignments can provoke these sensations at a resonant characteristic point with certain pitches and loudness levels, and send the whole system in disarray, producing distortion in the perception with the extra-energy that is directed into the cochlea. Sometimes with very careful middle ear studies you can turn up unusual patterns when using different frequency stimulations. The issue with hyperacusis needs further investigation as the perception of loudness tolerance must be distinguished from the irritation associated with the 'overload' sensation. Hyperacusis is typically reduced tolerances by discrete frequencies measured by careful interrupted presentations, one ear at a time, from 500 Hz to 8000 Hz. Normal tolerances for these tones should be close to 100 dB or higher. Collapsed loudness tolerance in one ear is unusual, most often, when present, it is a bilateral condition. If the middle ear ossicles end up becoming an area of focus, I recall an otologist who went in with surgery and carefully packed the stapes with some material to tighten up the 'wobble'. Unfortunately, in that case, the problem did not abate. As a final note, I would encourage you to determine if the neural ganglia are firing on that side, using electrochocleography and emissions to check for outer hair cell function.
Marsha Johnson, AuD, works in her facility, the Oregon Tinnitus & Hyperacusis Treatment Clinic, in Portland, Oregon, est 1997. Visit www.tinnitus-audiology.com for more information.