Human inner ear fluid imbalance detected by optical coherence tomography correlates with hearing loss.

Hearing loss and vertigo occur when there is an imbalance between the two inner ear fluids, endolymph and perilymph. The inner ear is a small delicate structure encased in dense bone deep in the base of the skull, making it challenging to image with high resolution. Because the fluid chambers are so small, there is no reliable way to measure their balance in a living patient to guide therapy. Here, we translated the technology of optical coherence tomography (OCT) for use in the human inner ear. Peering through the otic capsule bone during mastoid surgery, we imaged the lateral and posterior semicircular canals of patients with Ménière's disease or vestibular schwannoma and measured the endolymph-to-perilymph ratio. Compared with normal controls, both patient groups demonstrated increased endolymph and reduced perilymph, a disorder termed endolymphatic hydrops. OCT imaging demonstrated good repeatability for measuring the endolymph-to-perilymph ratio. Our data indicate that increased endolymph-to-perilymph ratios correlated with the degree of hearing loss. Thus, small yet meaningful changes in inner ear fluid balance are detectable with this approach with better resolution than gadolinium-enhanced 3 Tesla magnetic resonance imaging, the current gold standard clinical imaging modality. Our findings support the feasibility of imaging the human inner ear during surgical procedures with OCT and demonstrate the ability to detect endolymphatic hydrops. Moreover, this technique permits the measurement of the fluid chambers within the inner ear in real time during surgical procedures with adequate sensitivity to guide the management of complex but common ear diseases.