Hearing loss screening and monitoring is an important part of general health monitoring. In addition, in some cases hearing damage can be reduced or prevented by early detection. For example, certain drugs, such as those used in the treatment of cancer, can be damaging to hearing, to auditory sensory cells and spiral ganglion neurons. Damage typically occurs first in the more basal regions of the cochlea which are specific for high-frequency hearing, and progresses to more apical regions that are relevant to speech understanding.
Monitoring of high-frequency hearing loss can be an effective means for early detection of hearing problems, including those caused by ototoxicity. Through early detection, for example, oncologists and others can adjust drug dosages or, alternatively, switch to medications that are less ototoxic. Despite substantial evidence and clear implications that preventing significant post-treatment hearing loss improves outcomes for patients, early identification and monitoring practices have not been implemented as a standard of care in most medical centers largely due to limitations in audiometric testing equipment. Currently available equipment requires patients to be seen in an audiology clinic for testing in a sound-attenuated room, which is generally not practical for patients undergoing treatment for cancer since these individuals often are severely ill or fatigued, or else live in rural areas and it is not realistic to expect them to return to the clinic to have their hearing tested. Accordingly, improvements in early hearing loss identification and monitoring to reduce and/or prevent permanent hearing loss are desirable. Because exposure to ototoxins and high levels of noise cause hearing loss primarily by damaging the outer hair cells and spiral ganglion neurons within the cochlea, non-invasive tests of outer hair cell function and neural survival are also needed.