by Haley Otman
Patients who complain they can’t hear their friends at a noisy restaurant, but pass a hearing test in their doctor’s office, may be describing hidden hearing loss.
Now, less than six years since its initial description, scientists have made great strides in understanding what hidden hearing loss is and what causes it. In research published in Nature Communications, University of Michigan researchers report a new unexpected cause for this auditory neuropathy, a step toward the eventual work to identify treatments.
“If people can have hidden hearing loss for different reasons, having the ability to make the right diagnosis of the pathogenesis will be critical,” says author Gabriel Corfas, Ph.D., director of the Kresge Hearing Research Institute at Michigan Medicine’s Department of Otolaryngology – Head and Neck Surgery.
Corfas published the research with co-author Guoqiang Wan, now with Nanjing University in China. They discovered using mice that disruption in the Schwann cells that make myelin, which insulates the neuronal axons in the ear, leads to hidden hearing loss. This means hidden hearing loss could be behind auditory deficits seen in acute demyelinating disorders such as Guillain-Barré syndrome, which can be caused by Zika virus.
Corfas and Wan used genetic tools to induce loss of myelin in the auditory nerve of mice, modeling Guillain-Barré. Although the myelin regenerated in a few weeks, the mice developed a permanent hidden hearing loss. Even after the myelin regenerated, damage to a nerve structure called the heminode remained.