Background and Objectives: Electrode migration after cochlear implantation (CI) is a rare complication that accounts for 1to 15% of all revision surgery. This study is a systematic review of the literature for investigating the knowledge and approaches to the incidence of electrode migration after CI. Methods: A systematic electronic search of the literature was carried out using PubMed, Cochrane, Virtual Health Library, Scopus and Web of Science (ISI). All original articles that reported electrode migration after CI surgery were included. The Newcastle-Ottawa Scale and CARE checklist were utilized for the assessment of the risk of bias. Descriptive data analysis was performed using SPSS software. Results: A total of 26 studies including 4,316 patients were included. Out of them, 289 patients had electrode migration following CI. To diagnose electrode migration, traditional computed tomography scan was used in 13 studies, while cone-beam computed tomography was applied in three studies. In addition, electrode migration was detected during intraoperative exploration in eight studies. The most common presenting symptom was change in sound/poor performance (n = 43) followed by pain sensation (n = 15) and facial nerve stimulation (n = 10). Cholesteatoma was the most common associated pathology (n = 10) followed by infection (n = 9) and ossification of the basal turn of the cochlea (n = 8). Conclusion: Electrode migration is a major complication of CI and could be more common than previously thought. As it may occur with or without clinical complaints, long-term follow-up through routine radiological scanning is recommended. Further studies are warranted to identify the underlying mechanism of electrode extrusion and the appropriate fixation method.

No abstract

The mathematical equations to estimate cochlear duct length (CDL) using cochlear parameters such as basal turn diameter (A-value) and width (B-value) are currently applied for cochleae with two and a half turns of normal development. Most of the inner ear malformation (IEM) types have either  less than two and a half cochlear turns or have a cystic apex, making the current available CDL equations unsuitable for cochleae with abnormal anatomies. Therefore, this study aimed to estimate the basal turn length (BTL) from the cochlear parameters of different anatomical types, including normal anatomy; enlarged vestibular aqueduct; incomplete partition types I, II, and III; and cochlear hypoplasia. The lateral wall was manually tracked for 360° of the angular depth, along with the A and B values in the oblique coronal view for all anatomical types. A strong positive linear correlation was observed between BTL and the A- (r2 = 0.74) and B-values (r2 = 0.84). The multiple linear regression model to predict the BTL from the A-and B-values resulted in the following equation (estimated BTL = [A × 1.04] + [B × 1.89] − 0.92). The manually measured and estimated BTL differed by 1.12%. The proposed equation could be beneficial in adequately selecting an electrode that covers the basal turn in deformed cochleae.