Scala tympani cochleostomy for cochlear implantation

Vestibular Organ and Cochlear Implantation-A Synchrotron and Micro-CT Study

Background: Reports vary on the incidence of vestibular dysfunction and dizziness in patients following cochlear implantation (CI). Disequilibrium may be caused by surgery at the cochlear base, leading to functional disturbances of the vestibular receptors and endolymphatic duct system (EDS) which are located nearby. Here, we analyzed the three-dimensional (3D) anatomy of this region, aiming to optimize surgical approaches to limit damage to the vestibular organ. Material and Methods: A total of 22 fresh-frozen human temporal bones underwent synchrotron radiation phase-contrast imaging (SR-PCI). One temporal bone underwent micro-computed tomography (micro-CT) after fixation and staining with Lugol's iodine solution (I2KI) to increase tissue contrast. We used volume-rendering software to create 3D reconstructions and tissue segmentation that allowed precise assessment of anatomical relationships and topography. Macerated human ears belonging to the Uppsala collection were also used. Drilling and insertion of CI electrodes was performed with metric analyses of different trajectories. Results and Conclusions: SR-PCI and micro-CT imaging demonstrated the complex 3D anatomy of the basal region of the human cochlea, vestibular apparatus, and EDS. Drilling of a cochleostomy may disturb vestibular organ function by injuring the endolymphatic space and disrupting fluid barriers. The saccule is at particular risk due to its proximity to the surgical area and may explain immediate and long-term post-operative vertigo. Round window insertion may be less traumatic to the inner ear, however it may affect the vestibular receptors.

Assessment of Speech Understanding After Cochlear Implantation in Adult Hearing Aid Users: A Nonrandomized Controlled Trial

Importance

Cochlear implants were approved for use in adults in the 1980s, but use remains low owing to a lack of awareness regarding cochlear implantation candidacy criteria and expected outcomes. There have been limited, small series examining the safety and effectiveness of cochlear implantation in adult hearing aid (HA) users with and without mild cognitive impairment (MCI).

Objective

To investigate the safety and effectiveness of a single-ear cochlear implant in a group of optimized adult HA users with and without MCI across a variety of domains.

Design, Setting, and Participants

In this nonrandomized controlled trial, a multicenter, prospective, repeated-measures investigation was conducted at 13 US institutions. The setting was academic and community-based cochlear implant programs. Eligible participants were 100 adults (aged >18 years) with postlinguistic onset of bilateral moderate sloping to profound or worse sensorineural hearing loss (≤20 years' duration). Fluent English speakers underwent an optimized bilateral HA trial for at least 30 days. Individuals with aided Consonant-Vowel Nucleus-Consonant (CNC) word score in quiet of 40% or less correct in the ear to be implanted and 50% or less correct in the contralateral ear were offered cochlear implants. The first participant was enrolled on February 20, 2017, and the last participant was enrolled on May 3, 2018. The final follow-up was on December 21, 2018.

Interventions

Participants received the same cochlear implant system and contralateral HA.

Main Outcomes and Measures

The primary outcome measure was speech understanding in quiet (CNC word score) using both the cochlear implant and opposite ear HA. Secondary outcome measures included the following: adverse events; speech understanding in noise (AzBio signal-to-noise ratio of +10 db [+10 SNR]) Health Utilities Index Mark 3 (HUI3); Speech, Spatial, and Qualities of Hearing Questionnaire 49 (SSQ49); and Montreal Cognitive Assessment (MoCA).

Results

The median age at cochlear implantation of the 96 patients included in the trial was 71 years (range, 23-91 years), and 62 patients (65%) were male. Three serious adverse events requiring revision surgery occurred, and all resolved without sequelae. By 6 months after activation, the absolute marginal mean change in CNC word score and AzBio +10 SNR was 40.5% (95% CI, 35.9%-45.0%) and 24.1% (95% CI, 18.9%-29.4%), respectively. Ninety-one percent (87 of 96) of participants had a clinically important improvement (>15%) in the CNC word score in the implant ear. Mild cognitive impairment (MoCA total score ≤25) was observed in 48 of 81 study participants (59%) at baseline. Speech perception marginal mean improvements were similar between individuals with and without baseline MCI, with values of 40.9% (95% CI, 35.2%-46.6%) and 39.6% (95% CI, 31.8%-47.4%), respectively, for CNC word score and 27.5% (95% CI, 21.0%-33.9%) and 17.8% (95% CI, 9.0%-26.6%), respectively, for AzBio +10 SNR. Statistically significant and clinically important improvements in the HUI3 and SSQ49 were evident at 6 months.

Conclusions and Relevance

The findings of this nonrandomized controlled trial seem to indicate that cochlear implants are safe and effective in restoring speech understanding in both quiet and noise and improve quality of life in individuals with and without MCI.

Trial Registration

ClinicalTrials.gov Identifier: NCT03007472.

Effects of Various Trajectories on Tissue Preservation in Cochlear Implant Surgery: A Micro-Computed Tomography and Synchrotron Radiation Phase-Contrast Imaging Study

OBJECTIVES

The purpose of this study was to evaluate the three-dimensional (3D) anatomy and potential damage to the hook region of the human cochlea following various trajectories at cochlear implantation (CI). The goal was to determine which of the approaches can avoid lesions to the soft tissues, including the basilar membrane and its suspension to the lateral wall. Currently, there is increased emphasis on conservation of inner ear structures, even in nonhearing preservation CI surgery.

DESIGN

Micro-computed tomography and various CI approaches were made in an archival collection of macerated and freshly fixed human temporal bones. Furthermore, synchrotron radiation phase-contrast imaging was used to reproduce the soft tissues. The 3D anatomy was investigated using bony and soft tissue algorithms, and influences on inner ear structures were examined.

RESULTS

Micro-computed tomography with 3D rendering demonstrated the topography of the round window (RW) and osseous spiral laminae, while synchrotron imaging allowed reproduction of soft tissues such as the basilar membrane and its suspension around the RW membrane. Anterior cochleostomies and anteroinferior cochleostomies invariably damaged the intracochlear soft tissues while inferior cochleostomies sporadically left inner ear structures unaffected.

CONCLUSIONS

Results suggest that cochleostomy approaches often traumatize the soft tissues at the hook region at CI surgery. For optimal structural preservation, the RW approach is, therefore, recommended.

On the anatomy of the 'hook' region of the human cochlea and how it relates to cochlear implantation

BACKGROUND

The optimal insertion route for an electrode array in hearing preservation cochlear implantation (CI) surgery is still tentative. Both cochleostomy (CO) and round window (RW) techniques are used today. In the present study we analyzed size variations and topographic anatomy of the 'hook' region of the human cochlea to better comprehend the Testo effects of various electric array insertion modes.

MATERIAL AND METHODS

Size variations of the cochlear 'hook' region were assessed in 23 human, microdissected temporal bones by measuring the distances between the oval and round windows, also outlining the spiral ligament/spiral lamina. Influence of size variations on spiral ligament position and fundamentals for different surgical approaches were evaluated in a subset of 'small' and 'large' cochleae performing different types of CO. In addition, the relationship between the microdissected accessory canal housing the inferior cochlear vein and the RW was analyzed.

RESULTS

The lateral vestibular wall and the cochlear 'hook' displayed large anatomic variations that greatly influenced the size of the potential surgical area. RESULTS showed that only very inferiorly located CO entered the scala tympani without causing trauma to the spiral ligament and spiral lamina. An inferior approach may challenge the inferior cochlear vein.

CONCLUSION

Preoperative assessment of the distance between the round and oval windows may direct the surgeon before CI hearing-preservation surgery. CO techniques, especially in 'small' ears, may lead to frequent damage to the inner ear structures. In those cases with substantial residual hearing, CI surgery may be better performed through a RW approach.

Semiautomatic cochleostomy target and insertion trajectory planning for minimally invasive cochlear implantation

A major component of minimally invasive cochlear implantation is atraumatic scala tympani (ST) placement of the electrode array. This work reports on a semiautomatic planning paradigm that uses anatomical landmarks and cochlear surface models for cochleostomy target and insertion trajectory computation. The method was validated in a human whole head cadaver model (n = 10 ears). Cochleostomy targets were generated from an automated script and used for consecutive planning of a direct cochlear access (DCA) drill trajectory from the mastoid surface to the inner ear. An image-guided robotic system was used to perform both, DCA and cochleostomy drilling. Nine of 10 implanted specimens showed complete ST placement. One case of scala vestibuli insertion occurred due to a registration/drilling error of 0.79 mm. The presented approach indicates that a safe cochleostomy target and insertion trajectory can be planned using conventional clinical imaging modalities, which lack sufficient resolution to identify the basilar membrane.

Comparison of Cochlear Implant Performance after Round Window Electrode Insertion Compared with Traditional Cochleostomy

Objective

To compare speech perception after undergoing round window (RW) electrode insertion with those who underwent traditional cochleostomy (C) cochlear implant (CI) surgery.

Study Design

Case series with chart review.

Setting

Academic cochlear implant center.

Subjects

Patients who met CI criteria with favorable intraoperative RW anatomy who underwent RW CI electrode insertion. Patients who underwent traditional C surgery were matched for age, duration of deafness, and preoperative hearing.

Methods

Postoperative speech performance using the consonant-nucleus-consonant (CNC) test, Northwestern University Children’s Perception of Speech (NUCHIPS), and Hearing in Noise Test (HINT) between 3 and 48 months after CI.

Results

A total of 84 patients underwent RW insertion between 2004 and 2011. Of these, 55 had pre- and postoperative speech perception data for analysis. Average age of implantation ranged from 2.4 to 87.3 years (mean ± SD, 42.1 ± 24.2 years) for RW patients. Average age of implantation for matched traditional C patients ranged from 2.3 to 85.6 years (mean ± SD, 43.3 ± 25.0 years). No significant differences in postoperative CI speech perception scores were noted between the RW and C groups at 12 months post-CI (RW group, 55.28% ± 23.26% vs C group, 53.19% ± 24.14%; P = .70).

Conclusion

Our study found that patients with favorable RW anatomy who underwent RW CI electrode insertion demonstrated comparable speech perception compared with the traditional cochleostomy insertion group.

Cochlear implantation and hearing preservation: Results in 21 consecutively operated patients using the round window approach

CONCLUSION

Prevalent hearing conservation may be achieved after round window (RW) cochlear implantation using soft and flexible electrode arrays if variations of RW anatomy, topography, and facial nerve position are considered. The most favorable electrode insertion depth remains to be established.

OBJECTIVES

We assessed the incidence of cochlear function after cochlear implant (CI) electrode insertion through the RW in our first 21 consecutively operated patients aimed at hearing conservation.

METHODS

Eleven patients had a preoperative low frequency hearing suitable for electro-acoustic stimulation. Hearing was preserved in an additional nine patients at their request with the intention to use full frequency CI stimulation. Anatomic variations of the RW were carefully considered using our temporal bone collection of micro-dissected ears. Electrode extension was assessed on X-ray by measuring the insertion angle of the first electrode and intra-cochlear length and correlated with audiometric data.

RESULTS

There was no incidence of total loss of residual hearing in any of the patients. A slight deterioration of low frequency thresholds occurred in some patients. Mean hearing loss at 125-500 Hz was 14.4 dB at 1 month following surgery and 15.6 dB after 1 year. Insertion angle (300-540°) and depth (17.5-28.5 mm) were not statistically correlated to hearing loss.