Novel Biomedical Imaging Systems for Diagnosing Hearing Loss

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Age-related hearing loss (ARHL) is the predominant sensory disorder and neurodegenerative condition of our aged population. Currently, it is difficult or impossible to diagnose the exact etiology of ARHL, or other types of hearing loss in a particular patient clinically. This makes effective medical interventions for hearing loss quite challenging now, and indeed, there are no FDA-approved medical treatments to prevent or treat sensorineural hearing loss. The endocochlear potential (EP), also known as the “cochlear battery”, is the voltage difference between the endolymph of scala media and the surrounding fluids of the other two cochlear scalae. The EP results from the high K+ and low Na+ concentrations in the endolymph due to movement of K ions up a voltage and concentration gradient by specialized cells of the stria vascularis of the cochlear lateral wall. This voltage difference is critical for normal functioning of the inner ear, and good hearing. There are reports from animal model studies demonstrating the significance of the EP for hearing, and how it declines in the aging cochlea, with downstream effects on other cochlear pathologies as well. However, for human diagnoses, there is no clinical method available for EP measurements. Post-mortem EP measurements in human cadavers, for research purposes, are also not feasible, as mammals lose the EP immediately after they die. Currently, a surgical approach for rodents – exposing the bulla and cochlea, and measuring the EP using a microelectrode, is the gold standard for EP measurement in animal models. However, this approach cannot be utilized in humans due to its invasive characteristics, causing both permanent loss of hearing and surrounding tissue damage, while also being terminal in nature for rodents. This complication makes longitudinal human studies impossible, thus, hindering the firm establishment of strial atrophy and EP reduction as a predominant clinical risk factor in ARHL and other types of hearing impairment. Therefore, there is a compelling need to develop an in vivo, wireless EP measurement technique that could be utilized for human subjects. The primary aim of this project is to develop a dependable EP measurement methodology using current nuclear and molecular imaging methods in which a dilute radiotracer can be used to characterize K+ activity within the inner ear. The proposed research has a unique potential to revolutionize the diagnostic and treatment possibilities for hearing loss clinically. We combine biomedical engineering and imaging, with hearing sciences, animal model techniques and neuroengineering to achieve this translational breakthrough for hearing impaired persons.