Tinnitus, the perception of ringing or buzzing when no external sound exists, affects an estimated 15 percent of people worldwide. Until now, doctors have had no objective test for it. Diagnosis depended entirely on what a patient reported hearing.
A new study offers a possible way to change that. Researchers at the University of Connecticut measured a protein called prestin in the blood of 82 adults, half of whom had tinnitus. Those with the condition had concentrations about 50 percent higher than those without it.
Why prestin
Prestin is a motor protein found in the membranes of outer hair cells in the cochlea, the spiral structure of the inner ear. It helps amplify sound and is essential for sensitive hearing. Earlier work has linked the protein to hearing damage, and animal models show its levels change after acoustic trauma.
Studies have also shown that prestin levels shift with noise exposure, age and hearing loss. An aspirin overdose, long known to cause temporary hearing problems, disrupts cochlear function and affects prestin among other proteins. All of this made it a reasonable candidate for a marker of injury to the inner ear.
Proof of concept, not a test yet
The lead author, otolaryngologist Kourosh Parham, described the result as proof of concept that an ear protein may play a central role in how tinnitus develops and is managed. He said the work is a first step toward drugs that could help control the condition.
The study is small, and a blood marker is only useful if it separates tinnitus from other kinds of hearing damage. Many people with hearing loss do not have tinnitus, and many with tinnitus have normal audiograms. Larger trials will need to show whether prestin levels track symptoms over time, and whether they fall when a treatment works.
What patients should take from it
There is no new treatment to ask for yet. The practical value is that a field which has relied on self-report may finally get a measurement. That would help researchers test drugs faster and help clinicians distinguish tinnitus from other causes of phantom sound.
The findings were published in Otolaryngology - Head and Neck Surgery.