Potential Implications of Slim Modiolar Electrodes for Severely Malformed Cochleae: A Comparison With the Straight Array With Circumferential Electrodes

Abstract

Objectives: Malformations of the inner ear account for approximately 20% of congenital deafness. In current practice, the straight arrays with circumferential electrodes (i.e., full-banded electrodes) are widely used in severely malformed cochlea. However, the unpredictability of the location of residual spiral ganglion neurons in such malformations argues against obligatorily pursuing the full-banded electrode in all cases. Here, we present an experience of electrically evoked compound action potential (ECAP) and radiography-based selection of an appropriate electrode for severely malformed cochlea. Methods: Three patients with the severely malformed cochlea, showing cochlear hypoplasia type II (CH-II), incomplete partition type I (IP-I), and cochlear aplasia with a dilated vestibule (CADV), were included, and the cochlear nerve deficiency (CND) was evaluated. Full-banded electrode (CI24RE(ST)) and slim modiolar electrode (CI632) were alternately inserted to compare ECAP responses and electrode position. Results: In patient 1 (CH-II with CND) who had initially undergone cochlear implantation (CI) using the lateral wall electrode (CI422), a revision CI was performed due to incomplete insertion of CI422 and resultant unsatisfactory performance, thus explanting the CI422 and re-inserting the CI24RE(ST) and CI632 sequentially. Although both electrodes elicited reliable ECAP responses with correct positioning, CI24RE(ST) showed overall lower ECAP thresholds compared to CI632; thus, CI24RE(ST) was selected. In patient 2 (IP-I with CND), CI632 elicited superior ECAP responses relative to CI24RE(ST), with correct positioning of the electrode; CI632 was chosen. In patient 3 (CADV), CI632 did not elicit an ECAP response while meaningful ECAP responses were obtained with the CI24RE(ST) array once correct positioning was achieved. All patients markedly improved auditory performance postoperatively. Conclusion: ECAP and radiography-based strategy for an appropriate electrode may be useful for severely malformed cochlea, leading to enhanced functional outcomes. Additionally, the practice of sticking to the full-banded straight electrode may not always be the best for IP-I and CH-II.

Long‐term audiologic outcomes and potential outcome predictors of cochlear implantation in cochlear aplasia with dilated vestibule: A case series

“…It should also be noted that adjusting the position of the electrodes in the CADV ear can improve the ECAP response. 4 This study has an intrinsic limitation stemming from the inclusion of too few subjects to draw a firm conclusion.…”

“…Audiologic outcome measures, including the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) and CAP, were analysed for all patients as previously described. 4 CAP is a widely used, validated parameter of auditory receptive ability, 6 and the IT-MAIS score was evaluated preoperatively and postoperatively to assess the child's spontaneous responses to sound in everyday situations through a structured interview provided by the child's parents. 7 To evaluate speech performance in older children and adolescents, monosyllabic word and sentence recognition scores were measured using Korean phonetically balanced (PB) words and the Korean version of the Central Institute for the Deaf (K-CID) sentences, respectively, by an experienced speech therapist.…”

“…Bong Jik Kim 1 Hyoungwon Jeon 2 Yehree Kim 2 Sang-Yeon Lee 3 Jin Hee Han 1,2 Nayoung Yi 1 Jong Woo Chung 4 Seung-Ha Oh 3,5 Byung Yoon Choi…”

How to Maximize the Outcomes of Cochlear Implantation in Common Cavity and Cochlear Aplasia With Dilated Vestibule, the Most Severe Inner Ear Anomalies?

“…The fibers of the common cochleovestibular nerve or auditory tissues are thought to be distributed along the cavity wall of these anomalies [ 6 ]. This has been clinically and electrophysiologically supported by a recent observation that a full-band straight electrode clearly outperformed modiolar hugging electrodes in eliciting electrically evoked compound action potential (ECAP) responses in CADV [ 7 ]. Specifically, Yamazaki et al [ 8 ] evaluated the spatial distribution of auditory neuronal tissue in CC deformities by electrical auditory brainstem response recording and suggested that the auditory neuronal tissue is distributed in the anteroinferior part of CC deformities.…”

“…In their study, one subject whose CI electrode failed to contact the inner wall of the CC cavity showed only limited performance compared to others whose electrodes were in sufficient contact with the periphery of the cavity, albeit with some of the electrode tips being placed in the internal auditory canal or anterior semicircular canal [ 9 ]. In line with this, Lee and Choi [ 7 ] proposed advantages of ECAP-based positioning of full-band straight electrodes in CC/CADV cases. Indeed, they proved that a different position of the full-band straight electrode can lead to a different degree of ECAP response in the same CADV cavity.…”