Electrode array design determines scalar position, dislocation rate and angle and postoperative speech perception

Abstract

Purpose The aim of this study is to examine the scalar dislocation rate in straight and perimodiolar electrode arrays in relation to cochlear morphology. Furthermore, we aim to analyze the specific dislocation point of electrode arrays depending on their design and shape and to correlate these results to postoperative speech perception. Methods We conducted a comparative analysis of patients (ears: n = 495) implanted between 2013 and 2018 with inserted perimodiolar or straight electrode arrays from Cochlear™ or MED-EL. CBCT (cone beam computed tomography) was used to determine electrode array position (scalar insertion, intra-cochlear dislocation, point of dislocation and angular insertion depth). Furthermore, cochlear morphology was measured. The postoperative speech discrimination was compared regarding electrode array dislocation, primary scalar insertion and angular insertion depth. Results The electrode array with the highest rate of primary SV insertions was the CA; the electrode array with the highest rate of dislocations out of ST was the FlexSoft. We did not find significantly higher dislocation rates in cochleostomy-inserted arrays. The angle of dislocation was electrode array design-specific. A multivariate nonparametric analysis revealed that the dislocation of the electrode array has no significant influence on postoperative speech perception. Nevertheless, increasing angular insertion depth significantly reduced postoperative speech perception for monosyllables. Conclusion This study demonstrates the significant influence of electrode array design on scalar location, dislocation and the angle of dislocation itself. Straight and perimodiolar electrode arrays differ from each other regarding both the rate and place of dislocation. Insertion via cochleostomy does not lead to increased dislocation rates in any of the included electrode arrays. Furthermore, speech perception is significantly negatively influenced by angular insertion depth.

Systematic Review of Intracochlear Measurements and Effect on Postoperative Auditory Outcomes after Cochlear Implant Surgery

“…Of 3,091 electrodes, there were 1,646 perimodiolar and 1,445 straight electrodes. There were 20 cohort studies (6,9,12,14,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), 10 case series (5,(10)(11)(12)(36)(37)(38)(39)(40)(41), and 2 cross-sectional studies (42,43). A graphical representation of each measurement is depicted in Figure 2, and a summary of the number of studies with the salient correlation is depicted in Figure 3.…”

“…Only one study examined perimodiolar electrodes independently, where 36 cochlear CA electrodes demonstrated no correlation with CNC scores, although this did not achieve significance (28). Four studies (n = 669) in straight and perimodiolar electrodes (9,25,26,38) demonstrated negative correlation between AngI and auditory outcomes. Finley et al (38) identified a significant ( p = 0.00) negative correlation with CNC word scores in AB electrodes.…”

“…Eighteen studies (n = 2,115) with 19 distinct populations reported on ScaT (Table 3) (6,9,10,14,22,23,(25)(26)(27)30,31,(34)(35)(36)38,40,42,43). Twelve studies (n = 857) demonstrated negative correlation of ScaT on auditory outcomes (6,9,10,14,23,25,27,30,35,36,38,40).…”

“…Oxford CEBM level of evidence ranged between levels 2 and 4 (44). There were 6 prospective cohort studies (level 2) (9,20,23,25,30,34), 15 retrospective cohort or cross-sectional studies (level 3) (6,12,14,22,24,(26)(27)(28)(29)(31)(32)(33)35,42,43), including two mixed retrospective and prospective studies (12,42), and 10 retrospective case series (level 4) (5,10,11,21,(36)(37)(38)(39)(40)(41). No randomized controlled trials or systematic reviews were identified.…”

Association between lateral wall electrode array insertion parameters and audiological outcomes in bilateral cochlear implantation

“…In the further course, various studies investigated the influence of possible location-related factors (e.g., angular insertion depth [AID], frequency-to-place mismatch [FPM] or angular separation) on the audiometric outcome in CI patients [7][8][9][10][11][12][13][14]. However, controversial opinions exist about the influence of the electrode insertion depth on speech recognition ranging from the significant benefit of deep insertion on speech perception [7,8,15,16] to absence of any association or negative influence [9,[17][18][19][20].…”