What is Complete Cochlear Coverage? How can my CI candidates benefit?
Complete Cochlear Coverage, one of the three components of Triformance, is the ability to electrically stimulate the cochlea from base to apex. Long, straight electrodes (28 to 31mm in length) can be inserted more deeply than shorter arrays and thus have the inherent advantage of extending the range of electrical stimulation into the apical region. Therefore, they not only provide a broader range of cochlear locations, but also may allow a much better place pitch match than any shorter array. MED‑EL electrode arrays are available in many different lengths to fit each unique cochlea.
Cochlear implants are designed to filter incoming signals into different frequency bands which are transmitted to intracochlear, tonotopically distributed electrodes. Allocating frequency bands to electrode contacts in a way that the spectral information matches the tonotopic contact place is referred to as a “place pitch match.” There is a growing body of evidence to show that a better place pitch match leads to better sound quality (Zeitler, 2019). This could potentially allow some implant recipients to reach maximum levels of speech perception at faster rates (Dillon, 2019). An additional contribution to better speech understanding could be MED-EL’s optimized electrode spacing, resulting in wider channel separation and consequently in a larger number of physiologically effective independent channels. In general, when contacts are spaced farther apart, there is a better chance that the current fields will not negatively interact in ways that could make it difficult to distinguish one channel from its neighbor.
Many implant users report a “high, pitch” or “cartoon” sound quality upon initial stimulation of the cochlear implant. A shallow insertion and short electrode arrays can be partially responsible for this. Over time, perception can improve and is then often described as “normal,” or “more natural” by the recipient. Short electrode arrays produce a place mismatch, which some auditory systems can resolve to a greater or lesser degree. In fact, changes in perception can be dramatic (as much as 3 octaves), but this adaption can take years to occur. Providing a higher percentage of cochlear coverage by extending electrodes into the apical region may reduce the need for cortical re-mapping. Researchers have found that electrode arrays reaching the apical region provide a better initial place pitch match, which positively affects the patient's performance (O’Connell, 2016). In other words, with long electrode arrays, patients can achieve a more natural sound quality much more quickly than short arrays. Along with Complete Cochlear Coverage, FineHearing™ and Structure Preservation combine to create Triformance technology which allows MED-EL patients to perceive speech and music more naturally providing recipients the opportunity to reach their fullest hearing potential.
The potential for a better place pitch match achieved by a higher percentage of cochlear coverage is likely to suit all cochlear implant candidates, including the Single-Sided Deaf (SSD) population, due to the more natural low-frequency pitch provided by placing electrode contacts closer to the appropriately tuned region of the cochlea. A closer match to the contralateral, normal hearing ear should ease the learning process and increase acceptance of the implant since the perceived frequency range via electrical stimulation more closely matches the frequency range of the normal ear. MED-EL is the world’s first and only cochlear implant manufacturer to be granted FDA approval in the SSD and Asymmetric Hearing Loss (AHL) population.
Dillon, Margaret. “Low-Frequency Pitch Perception in Cochlear Implant Recipients with Normal Hearing in the Contralateral Ear.” Journal of Speech, Language and Hearing Research, vol. 62, 2860 – 2871. August 2019, https://doi.org/10.1044/2019_JSLHR-H-18-0409.
O’Connell, Brendan. “Electrode Location and Angular Insertion Depth are Predictors of Audiologic Outcomes in Cochlear Implantation.” Otology & Neurotology, vol. 37 (8), 1016 – 1023. September 2016, https://journals.lww.com/otology-neurotology/toc/2016/09000.
Zeitler, D. M., & Dorman, M. (2019). Cochlear Implantation for Single-Sided Deafness: A New Treatment Paradigm. Journal of Neurological Surgery, Part B: Skull Base, 80(2), 178-186. https://doi.org/10.1055/s-0038-1677482.