Objectives/Hypothesis Three surgical approaches: cochleostomy (C), round window (RW), and extended round window (ERW); and two electrodes types: lateral wall (LW) and perimodiolar (PM), account for the vast majority of cochlear implantations. The goal of this study was to analyze the relationship between surgical approach and electrode type with final intracochlear position of the electrode array and subsequent hearing outcomes. Study Design Comparative longitudinal study. Methods One hundred postlingually implanted adult patients were enrolled in the study. From the postoperative scan, intracochlear electrode location was determined and using rigid registration, transformed back to the preoperative computed tomography which had intracochlear anatomy (scala tympani and scala vestibuli) specified using a statistical shape model based on 10 microCT scans of human cadaveric cochleae. Likelihood ratio chi-square statistics were used to evaluate for differences in electrode placement with respect to surgical approach (C, RW, ERW) and type of electrode (LW, PM). Results Electrode placement completely within the scala tympani (ST) was more common for LW than were PM designs (89% vs. 58%; P < 0.001). RW and ERW approaches were associated with lower rates of electrode placement outside the ST than was the cochleostomy approach (9%, 16%, and 63%, respectively; P < 0.001). This pattern held true regardless of whether the implant was LW or PM. When examining electrode placement and hearing outcome, those with electrode residing completely within the ST had better consonant-nucleus-consonant word scores than did patients with any number of electrodes located outside the ST (P = 0.045). Conclusion These data suggest that RW and ERW approaches and LW electrodes are associated with an increased likelihood of successful ST placement. Furthermore, electrode position entirely within the ST confers superior audiological outcomes. Level Of Evidence 2b.

Objectives-1) Investigate the impact of electrode type and surgical approach on scalar electrode location in a large patient cohort; and 2) examine the relation between electrode location and postoperative audiologic performance. Setting-Tertiary academic hospital. Patients-220 post-lingually deafened adults undergoing cochlear implant (CI).Main Outcome Measures-Primary outcome measures of interest were scalar electrode location and postoperative audiologic performance.Results-In 68% of implants, electrodes were observed to be located solely in the scala tympani (ST). Multivariate analysis demonstrated perimodiolar(PM) and Mid-scala(MS) electrodes were p<0.001) times more likely to have at least one electrode in the scala vestibuli (SV) compared to lateral wall(LW) electrodes, respectively. Compared to cochleostomy(C), round window(RW) and extended round window(ERW) approaches demonstrated 70% reduction in SV insertion (OR 0.28,95%CI:0.1-0.8, p=0.01; ERW (OR O.28,95%CI:0.1-0.7, p=0.005). Examining postoperative audiometric performance, CNC score increased 0.6% with every 10° increase in angular insertion depth beyond the group minimum of 208° (Coefficient 0.0006,95%CI:0.0001-0.001, p=0.03). SV insertion was associated with a 12% decrease in CNC score (Coefficient -0.12,95%CI:-0.22--0.02, p=0.02). CNC score decreased 0.3% for every 1 year increase in age (Coefficient -0.003,95%CI:-0.006--0.0006), p=0.02). HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptConclusions-Electrode design and surgical approach were predictors of scalar electrode location. Specifically, LW electrodes showed higher rates of ST insertion compared to PM or MS. RW and ERW approaches showed higher rates of ST insertion when compared to C. In regards to performance, ST insertion, younger age, and greater angular insertion depth were predictors of improved CNC scores.

Over the last 20 years, cochlear implants (CIs) have become what is arguably the most successful neural prosthesis to date. Despite this success, a significant number of CI recipients experience marginal hearing restoration, and, even among the best performers, restoration to normal fidelity is rare. In this article, we present image processing techniques that can be used to detect, for the first time, the positions of implanted CI electrodes and the nerves they stimulate for individual CI users. These techniques permit development of new, customized CI stimulation strategies. We present one such strategy and show that it leads to significant hearing improvement in an experiment conducted with 11 CI recipients. These results indicate that image-guidance can be used to improve hearing outcomes for many existing CI recipients without requiring additional surgical procedures.

Cochlear implant surgery is a procedure performed to treat profound hearing loss. Clinical results suggest that implanting the electrode in the scala tympani, one of the two principal cavities inside the cochlea, may result in better hearing restoration. Segmentation of intra-cochlear cavities could thus aid the surgeon to choose the point of entry and angle of approach that maximize the likelihood of successful implant insertion, which may lead to more substantial hearing restoration. However, because the membrane that separates the intra-cochlear cavities is too thin to be seen in conventional in vivo imaging, traditional segmentation techniques are inadequate. In this work, we circumvent this problem by creating an active shape model with micro CT (μCT) scans of the cochlea acquired ex-vivo. We then use this model to segment conventional CT scans. The model is fitted to the partial information available in the conventional scans and used to estimate the position of structures not visible in these images. Quantitative evaluation of our method, made possible by the set of μCTs, results in dice similarity coefficients averaging 0.75. Mean and maximum surface errors average 0.21 and 0.80 mm.

The cochlear implant (CI) has been labeled the most successful neural prosthesis. Despite this success, a significant number of CI recipients experience poor speech understanding, and, even among the best performers, restoration to normal auditory fidelity is rare. While significant research efforts have been devoted to improving stimulation strategies, few developments have led to significant hearing improvement over the past two decades. We have recently introduced image processing techniques that open a new direction for advancement in this field by making it possible, for the first time, to determine the position of implanted CI electrodes relative to the nerves they stimulate using computed tomography images. In this article, we present results of an image-guided, patient-customized approach to stimulation that utilizes the electrode position information our image processing techniques provide. This approach allows us to identify electrodes that cause overlapping stimulation patterns and to deactivate them from a patient's map. This individualized mapping strategy yields significant improvement in speech understanding in both quiet and noise as well as improved spectral resolution in the 68 adult CI recipients studied to date. Our results indicate that image guidance can improve hearing outcomes for many existing CI recipients without requiring additional surgery or the use of ‘experimental' stimulation strategies, hardware or software. i 2014 S. Karger AG, Basel

The purpose of this work was to characterize expert variation in segmentation of intracranial structures pertinent to radiation therapy, and to assess a registration-driven atlas-based segmentation algorithm in that context. Eight experts were recruited to segment the brainstem, optic chiasm, optic nerves, and eyes, of 20 patients who underwent therapy for large space-occupying tumors. Performance variability was assessed through three geometric measures: volume, Dice similarity coefficient, and Euclidean distance. In addition, two simulated ground truth segmentations were calculated via the simultaneous truth and performance level estimation (STAPLE) algorithm and a novel application of probability maps. The experts and automatic system were found to generate structures of similar volume, though the experts exhibited higher variation with respect to tubular structures. No difference was found between the mean Dice coefficient (DSC) of the automatic and expert delineations as a group at a 5% significance level over all cases and organs. The larger structures of the brainstem and eyes exhibited mean DSC of approximately 0.8–0.9, whereas the tubular chiasm and nerves were lower, approximately 0.4–0.5. Similarly low DSC have been reported previously without the context of several experts and patient volumes. This study, however, provides evidence that experts are similarly challenged. The average maximum distances (maximum inside, maximum outside) from a simulated ground truth ranged from (−4.3, +5.4) mm for the automatic system to (−3.9, +7.5) mm for the experts considered as a group. Over all the structures in a rank of true positive rates at a 2 mm threshold from the simulated ground truth, the automatic system ranked second of the nine raters. This work underscores the need for large scale studies utilizing statistically robust numbers of patients and experts in evaluating quality of automatic algorithms.

OBJECTIVE Minimally-invasive image-guided approach to cochlear implantation (CI) involves drilling a narrow, linear tunnel to the cochlea. Reported herein is the first clinical implementation of this approach. STUDY DESIGN Prospective, cohort study. METHODS On preoperative CT, a safe linear trajectory through the facial recess targeting the scala tympani was planned. Intraoperatively, fiducial markers were bone-implanted, a second CT was acquired, and the trajectory was transferred from preoperative to intraoperative CT. A customized microstereotactic frame was rapidly designed and constructed to constrain a surgical drill along the desired trajectory. Following sterilization, the frame was employed to drill the tunnel to the middle ear. After lifting a tympanomeatal flap and performing a cochleostomy, the electrode array was threaded through the drilled tunnel and into the cochlea. RESULTS Eight of nine patients were successfully implanted using the proposed approach with six insertions completely within scala tympani. Traditional mastoidectomy was performed on one patient following difficulty threading the electrode array via the narrow tunnel. Other difficulties encountered included use of the back-up implant when an electrode was dislodged during threading via the tunnel, tip fold-over, and facial nerve paresis (House-Brackmann II/VII at 12 months) secondary to heat during drilling. Average time of intervention was 182±36 minutes. CONCLUSION Minimally-invasive, image-guided CI is clinically achievable. Further clinical study is necessary to address technological difficulties during drilling and insertion and to assess potential benefits including decreased time of intervention, standardization of surgical intervention, and decreased tissue dissection potentially leading to shorter recovery and earlier implant activation.

Objectives 1) Examine angular insertion depths (AID) and scalar location of MED-EL electrodes; and 2) determine the relationship between angular insertion depth (AID) and audiologic outcomes controlling for scalar position. Study Design Retrospective review. Methods Post-lingually deafened adults undergoing cochlear implantation with Flex 24, Flex 28, and Standard electrode arrays were identified. Patients with preoperative and postoperative CT scans were included, such that electrode location and AID could be determined. Outcome measures were 1) speech perception in the CI-only condition and 2) short-term hearing preservation. Results Forty-eight implants were included; all electrodes (48/48) were positioned entirely within the scala tympani. The median AID was 408°(IQ range 373-449°) for Flex 24, 575°(IQ range 465-584°) for Flex 28, and 584°(IQ range 368-643°) for Standard electrodes. The mean postoperative CNC score was 43.7%±21.9. A positive correlation was observed between greater AID and better CNC performance (r=0.48, p<0.001). Excluding patients with post-operative residual hearing, a strong correlation between AID and CNC persisted (r=0.57, p<0.001). In patients with pre-operative residual hearing, mean low-frequency PTA shift was 27 dB ± 14. A correlation between AID and low-frequency PTA shift at activation was noted (r=0.41, p=0.04). Conclusions Favorable rates of scala tympani insertion (100%) were observed. In the CI only condition, a direct correlation between greater AID and CNC score was noted regardless of post-operative hearing status. Deeper insertions were, however, associated with worse short-term hearing preservation. When patients without post-operative residual hearing were analyzed independently, the relationship between greater insertion depth and better performance was strengthened.