A Unique Perspective: Intrapatient Comparison of Perimodiolar and Lateral Wall Cochlear Implant Electrodes

Dear Prof. Lawrence Lustig, Editor-in-chief of Otology however, the difference is insignificant. This paper concludes that “Improved CNC scores with PM electrodes should be taken into account in addition to other factors such as patient anatomy, patient preference on manufacturer, and residual hearing when making the decision to choose between a PM and LW electrode.” This conclusion is premature and biased towards Cochlear(R) considering the following concerns. Perimodiolar (PM) electrodes, regardless of CI manufacturers, cover mostly the basal turn of the cochlea, whereas lateral wall (LW) electrode variants are available in lengths ranging from 15 to 34 mm, and it can cover a maximum of 2 full turns of the cochlea, depending on the length of the electrode inserted. Since in this study, they used only shorter-length LW electrode, the angular insertion depth will be shallower. This means the angular insertion depth, which is reported to be one of the several factors influencing hearing outcomes with CI1 is completely ignored in this study when making the conclusion. Age at implantation is another factor that influences hearing outcomes with CI. The LW electrode-implanted ear shows a higher age at implantation compared with the PM electrode-implanted ear. This could have influenced the PM electrode-implanted ear to hear better, which is completely ignored when making the conclusion. Follow-up time, which is another factor that influences hearing outcomes with CI. The LW electrode-implanted ear had only 3 years of follow-up compared with the PM electrode-implanted ear that had 7.7 years of follow-up. Again, this factor was completely ignored when making the conclusion. One of my other key concerns in this paper is that it prematurely considered every lateral wall electrode variant as identical, which is completely incorrect and concluded that the PM electrode outperforms the LW electrode. Please see the figure below that shows an angular insertion depth provided by different electrode variants.2 In the introduction section, the authors refer to previously published papers3–5 that support the author’s conclusion that the PM electrode outperforms the LW electrode. All these papers mostly use PM and LW electrodes from the same CI manufacturer, which is Cochlear(R), and it is known that their LW electrode is short in length to facilitate easy insertion and cannot cover more than the basal turn of the cochlea. This being the case, it is unfair to generalize that LW electrodes offer inferior hearing outcomes compared with PM electrodes. I ask the authors to clarify my concerns listed above in the best interest of the CI field, so that the CI field is not misled by this paper’s pre-mature conclusion, especially when choosing CI devices by patients.