Optimizing vestibular implant electrode positioning using fluoroscopy and intraoperative CT imaging

PURPOSE

 Vestibular implant electrode positioning close to the afferent nerve fibers is considered to be key for effective and selective electrical stimulation. However, accurate positioning of vestibular implant electrodes inside the semicircular canal ampullae is challenging due to the inability to visualize the target during the surgical procedure. This study investigates the accuracy of a new surgical protocol with real-time fluoroscopy and intraoperative CT imaging, which facilitates electrode positioning during vestibular implant surgery.

METHODS

 Single-center case-controlled cohort study with a historic control group at a tertiary referral center. Patients were implanted with a vestibulocochlear implant, using a combination of intraoperative fluoroscopy and cone beam CT imaging. The control group consisted of five patients who were previously implanted with the former implant prototype, without the use of intraoperative imaging. Electrode positioning was analyzed postoperatively with a high-resolution CT scan using 3D slicer software. The result was defined as accurate if the electrode position was within 1.5 mm of the center of the ampulla.

RESULTS

With the new imaging protocol, all electrodes could be positioned within a 1.5 mm range of the center of the ampulla. The accuracy was significantly higher in the study group with intraoperative imaging (21/21 electrodes) compared to the control group without intraoperative imaging (10/15 electrodes), (p = 0.008).

CONCLUSION

 The combined use of intraoperative fluoroscopy and CT imaging during vestibular implantation can improve the accuracy of electrode positioning. This might lead to better vestibular implant performance.

Practical tips by peer support in chronic vestibular hypofunction: an exploratory survey

Introduction

Patients with chronic vestibular hypofunction typically suffer from dizziness, imbalance and oscillopsia (blurred vision); symptoms that pose challenges to everyday life. Currently, advice on how to deal with such challenges is mainly provided by health care professionals (i.e., ENT-surgeons, neurologists, physiotherapists and psychologists). However, fellow patients with a similar condition and a true appreciation of the lived experiences, are likely to provide valuable support and advice as well. The purpose of this study, therefore, was to collect tips and advice from patients with chronic vestibular hypofunction.

Methods

An exploratory survey was designed to collect tips from fellow chronic vestibular hypofunction patients on how to cope with disease-related challenges in everyday life. The survey was distributed both online and in person. The list of tips was coded and analyzed thematically and deductively, by using the international classification of functioning, disability, and health (ICF) model.

Results

In total, 425 tips were obtained from the 179 participants. Most tips were coded under "environmental factors" (46%) and "activities and participation" (39%). The remaining tips were categorized as "body functions" (15%). No tips were about "body structures." The participants coped with their daily struggles by investing in assistive products and technology, like adapted bikes, special footwear, walking frames. They described the importance of ensuring minimal light intensity for visibility (i.e., installing light sources in dark places). During activities, participants gave the advice to avoid bumpy roads and obstacles, and highlighted the necessity of adequate visual fixation to maintain balance. To ensure optimal activity, participants emphasized the importance of managing energy and taking sufficient rest.

Discussion

This study gives insight into how patients with chronic vestibular hypofunction cope with everyday struggles due to their symptoms. These tips can expand advice given by healthcare professionals. Knowing that fellow patients experience similar struggles and learned to deal with their struggles in adequate ways, might offer support and help patients focus on possibilities rather than on disabilities. Further research should investigate the effect of sharing tips to see whether improvement in (mental) health can be achieved in patients with chronic vestibular hypofunction.

Evaluating hearing performance with cochlear implants within the same patient using daily randomization and imaging-based fitting - The ELEPHANT study

Background

Prospective research in the field of cochlear implants is hampered by methodological issues and small sample sizes. The ELEPHANT study presents an alternative clinical trial design with a daily randomized approach evaluating individualized tonotopical fitting of a cochlear implant (CI).

Methods

A single-blinded, daily-randomized clinical trial will be implemented to evaluate a new imaging-based CI mapping strategy. A minimum of 20 participants will be included from the start of the rehabilitation process with a 1-year follow-up period. Based on a post-operative cone beam CT scan (CBCT), mapping of electrical input will be aligned to natural place-pitch arrangement in the individual cochlea. The CI’s frequency allocation table will be adjusted to match the electrical stimulation of frequencies as closely as possible to corresponding acoustic locations in the cochlea. A randomization scheme will be implemented whereby the participant, blinded to the intervention allocation, crosses over between the experimental and standard fitting program on a daily basis, and thus effectively acts as his own control, followed by a period of free choice between both maps to incorporate patient preference. With this new approach the occurrence of a first-order carryover effect and a limited sample size is addressed.

Discussion

The experimental fitting strategy is thought to give rise to a steeper learning curve, result in better performance in challenging listening situations, improve sound quality, better complement residual acoustic hearing in the contralateral ear and be preferred by recipients of a CI. Concurrently, the suitability of the novel trial design will be considered in investigating these hypotheses.

Trial registration

ClinicalTrials.gov: NCT03892941. Registered 27 March 2019.

The Benefits of Bimodal Aiding on Extended Dimensions of Speech Perception: Intelligibility, Listening Effort, and Sound Quality

The benefits of combining a cochlear implant (CI) and a hearing aid (HA) in opposite ears on speech perception were examined in 15 adult unilateral CI recipients who regularly use a contralateral HA. A within-subjects design was carried out to assess speech intelligibility testing, listening effort ratings, and a sound quality questionnaire for the conditions CI alone, CIHA together, and HA alone when applicable. The primary outcome of bimodal benefit, defined as the difference between CIHA and CI, was statistically significant for speech intelligibility in quiet as well as for intelligibility in noise across tested spatial conditions. A reduction in effort on top of intelligibility at the highest tested signal-to-noise ratio was found. Moreover, the bimodal listening situation was rated to sound more voluminous, less tinny, and less unpleasant than CI alone. Listening effort and sound quality emerged as feasible and relevant measures to demonstrate bimodal benefit across a clinically representative range of bimodal users. These extended dimensions of speech perception can shed more light on the array of benefits provided by complementing a CI with a contralateral HA.

Monaural Beamforming in Bimodal Cochlear Implant Users: Effect of (A)symmetric Directivity and Noise Type

OBJECTIVE

To evaluate monaural beamforming in bimodally aided cochlear implant (CI) users.

DESIGN

The study enrolled twelve adult bimodal listeners with at least six months of CI-experience and using a contralateral hearing aid (HA) most of the daytime. Participants were uniformly fitted with the same CI speech processor and HA, giving access to an identical monaural beamformer in both ears. A within-subject repeated measures design evaluated three directional configurations [omnidirectional, asymmetric directivity (in CI alone) and symmetric directivity (in both CI and HA)] in two noise types [stationary and fluctuating]. Bimodal speech reception thresholds (SRT) as well as listening effort ratings were assessed in a diffuse noise field.

RESULTS

Symmetric monaural beamforming provided a significant SRT improvement of 2.6 dB SNR, compared to 1.6 dB SNR for asymmetric monaural beamforming. Directional benefits were similarly observed in stationary and fluctuating noise. Directivity did not contribute to less listening effort in addition to improvement in speech intelligibility. Bimodal performance was about 7 dB SNR worse in fluctuating than in stationary noise.

CONCLUSIONS

Monaural beamforming provided substantial benefit for speech intelligibility in noise for bimodal listeners. The greatest benefit occurred when monaural beamforming was activated symmetrically in both CI and HA. Monaural beamforming does not bridge the gap between bimodal and normal hearing performance, especially in fluctuating noise. Results advocate further bimodal co-operation.

TRIAL REGISTRATION

This trial was registered in www.trialregister.nl under number NTR4901.