Age-related hearing loss is the most common form of hearing loss, affecting more than 70% of people over the age of 70. There are currently no medicines or other therapies available to prevent hearing loss or restore hearing – treatments are limited to hearing aids or cochlear implants, which bring benefit to many people, but don’t restore natural hearing.
There are many underlying causes of hearing loss. These include environmental damage, such as exposure to loud noise, or genetic causes. Different parts of the inner ear can be affected, such as the sound-sensing hair cells, the nerve cells which transmit information to the brain, or a part of the inner ear called the stria vascularis, which controls blood flow to the ear and maintains the endocochlear potential, which is needed for hair cells to signal to the brain. Different approaches will be needed to treat hearing loss caused by damage to these different parts of the ear. To do this, it is also important to know which part of the inner ear is damaged, so that people receive the correct treatment. As yet, we lack such accurate diagnostic tools.
The aim of the project is to develop a set of tests that can locate the damage within the inner ear of someone with hearing loss. To do this, the researchers will study mice with well-defined inner ear defects that cause progressive hearing loss (similar to age-related hearing loss), that are likely to reflect similar defects in the human inner ear. They will use a wide range of tests to measure how well the ear is working, using techniques that are already widely used to study hearing loss in people. These tests measure aspects of hearing such as someone’s ability to detect pitch and timing changes in sounds. These tests may give a better indication of how well someone can actually hear, as well as helping to locate the hearing loss within the inner ear.
The advantage of using these mice is that their hearing test results can be specifically matched to the site of damage in their inner ear, allowing researchers to identify changes in hearing performance that indicate where in the inner ear the damage is. This knowledge could then be transferred to people, and used as diagnostic tools for hearing loss.
The development of diagnostic tools that can distinguish between different types of inner ear damage will directly contribute to the development of medical treatments, as it will mean that clinical trials of new medicines can be tested only in those people who are most likely to benefit. In addition, once a broader range of treatments is available, these diagnostic tests will be invaluable in ensuring that people receive the most effective treatment for their hearing loss.