Cochlear Implant Candidacy and Surgical Considerations

Abstract

Numerous changes continue to occur in regard to cochlear implant candidacy. In general, these have been accompanied by concomitant and satisfactory changes in surgical techniques. Together, this has advanced the utility and safety of cochlear implantation. Most devices are now approved for use in patients with severe to profound rather the prior requirement of a bilateral profound loss. In addition, studies have begun utilizing short electrode arrays for shallow insertion in patients with considerable low frequency residual hearing. This technique will allow the recipient to continue to use acoustically amplified hearing for the low frequencies simultaneously with a cochlear implant for the high frequencies. New hardware, such as the behind-the-ear speech processors, require modification of existing implant surgery. Similarly, the new perimodiolar electrodes require special insertion techniques. Bilateral implantation clearly requires modification of the surgical techniques used for unilateral implantation. The surgery remains mostly the same, but takes almost twice as long, and requires some modification since at a certain point, when the first device is in contact with the body, the monopolar cautery may no longer be used. Research has already begun on the development of the totally implantable cochlear implant (TICI). This will clearly require a modification of the surgical technique currently used for the present semi-implantable devices. In addition to surgically burying the components of the present cochlear implant, we will also have to develop techniques for implanting a rechargeable power supply and a microphone for the TICI. The latter will be a challenge, since it must be placed where it is capable of great sensitivity, yet not exposed to interference or the risk of extrusion. The advances in design of, and indications for, cochlear implants have been matched by improvements in surgical techniques and decrease in complications. The resulting improvements in safety and efficacy have further encouraged the use of these devices. We anticipate further changes in the foreseeable future, for which there will likely be surgical problems to solve.

Pre-Operative Intravenous Dexamethasone Prevents Auditory Threshold Shift in a Guinea Pig Model of Cochlear Implantation

“…The success of cochlear implantation in patients with profound or total hearing loss has seen candidacy criteria relaxed to include patients with residual hearing [Kiefer et al, 1998;Cohen, 2004;Copeland and Pillsbury, 2004;Cullen et al, 2004;Dowell et al, 2004] who can receive synchronous amplification [Von Ilberg et al, 1999]. The protection of acoustic hearing during surgery has been attempted with soft surgical techniques [Lehnhardt, 1993;Gstoettner et al, 2004;Kiefer et al, 2004;James et al, 2005;Kiefer et al, 2005] and altered electrode designs [Gantz et al, 2005;Lenarz et al, 2006;Gstoettner et al, 2008]; however, there remains a complete loss of residual hearing in approximately 15% of cochlear implant recipients in recent series Kiefer et al, 2004;James et al, 2005;Balkany et al, 2006].…”

Acoustic–electric interactions in the guinea pig auditory nerve: Simultaneous and forward masking of the electrically evoked compound action potential

“…Recent advances in CI design, stimulation paradigms, and surgical techniques have led to changes in CI candidacy criteria, specifically, lowering the degree of hearing loss used as an indication for implantation. Consequently, patients with some degree of residual acoustic hearing are receiving CIs (NIH Consensus Statement, 1995;Cohen, 2004;Copeland & Pillsbury, 2004). The functionality of the remaining hair cells may be preserved in patients with residual hearing following implantation (Kiefer et al, 2002;Skarżyński et al, 2003;Gstoettner et al, 2006).…”

Bimodal Stimulation with Cochlear Implant and Hearing Aid in Cases of Highly Asymmetrical Hearing Loss

“…This piece of information is extremely important for the group of patients with AHL because an objective of bimodal adaptations is to obtain better sound perception and ensure hearing through one of the ears, in case the contralateral ear may suffer some type of degenerative pathology, as could potentially be the case with bilateral Meniere's disease [15] , autoimmune hearing loss [16] , otoesclerosis [17] , or some labyrinth malformations [18] . The stable PTA results had already been described by other authors [19,20] , and their homogeneity, regardless of the initial HLs, can be explained by several reasons: 1.) They reflect how the peripheral auditory pathway (superior olivar complex, inferior colliculus) is greatly involved in events of sound perception, and other more central factors of greater variability do not have an impact.…”