"Rounded Insertion": A Useful Cochlear Implantation Technique for Patients with Cochlear Hypoplasia Type I

Early activation after cochlear implantation: a systematic review

PURPOSE

To systematically review the outcomes of early activation following cochlear implantation (CI) based on the findings from different studies in the literature.

METHODS

A comprehensive search strategy was conducted through different databases to identify relevant articles. Our outcomes included impedance levels, rates of complications, hearing and speech perception performance, and patients' satisfaction levels.

RESULTS

The total number of included studies in this systematic review is 19, which recruited 1157 patients, including 857 who underwent early activation following CI. Seventeen studies investigated impedance levels or feasibility rates of early activation approaches. Most of these studies (n = 10) reported that mean impedance levels remarkably decreased within the first day-to-month (first measurement) post-activation. In addition, all 17 studies showed that impedance levels finally normalize and become comparable with intraoperative levels or the conventional activation group. Seventeen studies reported the occurrence of complications in their population. Ten of these studies indicated that none of their patients developed any post-operative complications after early activation. Seven studies reported the development of some minor complications, including pain 9.2% (28/304), infection 4.7% (13/275), swelling 8.2% (25/304), vertigo 15.1% (8/53), skin hyperemia 2.2% (5/228), and others 16.4% (9/55). Hearing and speech perception was assessed in six studies, which showed a remarkable improvement in their patients. Three studies investigated patients' satisfaction and showed high satisfaction levels. Only one report investigated the economic advantages of early activation.

CONCLUSION

Early activation is safe and feasible and does not impact the hearing and speech outcomes of the patients undergoing CI procedures.

Evolution of impedance values in cochlear implant patients after early switch-on

Cochlear implantation is currently the most effective treatment modality for severe to profound sensorineural hearing loss. Over the past few years, at the Department of Otolaryngology, Cheng Hsin General Hospital (Taipei, Taiwan), cochlear implant devices have been switched on within 24 hours of their implantation. Differences in impedance evolution after early switch-on for different devices have not been previously discussed. The present study aimed to investigate the impedance evolution of one device and the factors influencing this after early activation. Results are compared to published results of other devices. A total of 16 patients who received Advanced BionicsTM devices and had early activation within 24 hours of implantation, were included in the study. Impedance telemetry was recorded intraoperatively and postoperatively at 1 day, 1 week, 2 weeks, 4 weeks and 8 weeks. A stepwise increase was observed in the impedance evolution. To the best of our knowledge, the present study is the first to investigate the impedance evolution of the different devices after early switch-on within 24 hours of implantation and its influencing factors. Further research with a longitudinal design to compare the differences in electrode impedances between patients activated early versus those activated after a few weeks will be necessary for the disclosure of the underlying mechanisms.

Rounded Insertion Technique for Cochlear Implantation Surgery to Treat Cystic Inner Ear Malformation

OBJECTIVE

This article outlines the advantages and applicability of the rounded insertion technique of cochlear implants in patients with cystic inner ear malformation. This technique enables the insertion of the maximum number of electrodes and prevents the unwanted entry of electrodes into the internal auditory canal.

METHODS

We conducted a retrospective chart review of consecutive patients with cochlear hypoplasia (CH) and/or common cavity (CC) who underwent CI (cochlear implantation) via rounded insertion technique. The position of the electrode array in each patient was confirmed postoperatively via X-ray, and the number of functional electrodes was confirmed during the mapping process.

RESULTS

This study included five male and two female patients (median age: 3 years; age range: 2-7 years). Among the seven patients, four received a cochlear implant on the right side, one on the left side, and two bilaterally. Of the nine ears, six were cases of CH, and three were CC. All cochlear implant surgeries via rounded insertion technique were completed without complications. The maximum number of electrode contacts with fair function in the cystic cochlea was confirmed via postoperative X-ray and the subsequent mapping process.

CONCLUSION

This consecutive series of patients demonstrated the safety and reliability of rounded insertion technique for CI in patients with CH and/or CC.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2229-2233, 2020.

Differences in the impedance of cochlear implant devices within 24 hours of their implantation

Cochlear implantation is a surgical procedure, which is performed on severely hearing-impaired patients. Impedance field telemetry is commonly used to determine the integrity of the cochlear implant device during and after surgery. At the Department of Otolaryngology, Cheng Hsin General Hospital (Taipei, Taiwan), the cochlear implant devices are switched on within 24 hours of their implantation. In the present study, the impedance changes of Advanced Bionics^™ cochlear implant devices were compared with previous studies and other devices. The aim was to confirm previous hypotheses and to explore other potential associated factors that could influence impedance following cochlear implantation. The current study included 12 patients who underwent cochlear implantation at Cheng Hsin General Hospital with Advanced Bionics cochlear implant devices. The cochlear devices were all switched on within 24 hours of their implantation. The impedance was measured and compared across all contact channels of the electrode, both intra-operatively and post-operatively. The intra-operative impedance was compared with the switch-on impedance (within 24 hours of the cochlear implantation); the impedance was notably increased for all contact channels at switch-on. Of the 16 channels examined, 4 channels had a significant increase in impedance between the intra-operative measurement and the switch-on measurement. To the best of our knowledge, the impedance of a cochlear implant device can be affected by the diameter of the electrode, the position of the electrode arrays in the scala tympani, sheath formation and fibrosis surrounding the electrode after implantation and electrical stimulation during or after surgery. When the results of the current study were compared with previous studies, it was found that the impedance changes were opposite to that of Cochlear^™ implant devices. This may be explained by the position of the electrode arrays, sheath formation, the blow-out effect and differences in electrical stimulation.

Evolution of impedance field telemetry after one day of activation in cochlear implant recipients

OBJECTIVES

Changes in impedance between 24 hours and one month after cochlear implantation have never been explored due to the inability to switch on within one day. This study examined the effect of early activation (within 24 hours) on the evolution of electrode impedance with the aim of providing information on the tissue-to-electrode interface when electrical stimulation was commenced one day post implantation.

METHODS

We performed a retrospective review at a single institution. Patients who received a Nucleus 24RECA implant system (Cochlear, Sydney, Australia) and underwent initial switch-on within 24 hours postoperatively were included. Impedance measurements were obtained intraoperatively and postoperatively at 1 day, 1 week, 4 weeks, and 8 weeks.

RESULTS

A significant drop in impedance was noted 1 day after an initial activation within 24 hours followed by a significant rise in impedance in all channels until 1 week, after which the impedance behaved differently in different segments. Basal and mid-portion electrodes revealed a slight increase while apical electrodes showed a slight decrease in impedance from 1 week to 8 weeks postoperatively. Impedance was relatively stable 4 weeks after surgery.

CONCLUSIONS

This is the first study to report the evolution of impedance in all channels between initial mapping 1 day and 1 month after cochlear implantation. The underlying mechanism for the differences in behavior between different segments of the electrode may be associated with the combined effect of dynamics among the interplay of cell cover formation, electrical stimulation, and fibrotic reaction.