Stefan Weder

Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study

Objective Cochlear implants (CIs) are standard treatment for postlingually deafened individuals and prelingually deafened children. This human cadaver study evaluated diagnostic usefulness, image quality and artifacts in 1.5T and 3T magnetic resonance (MR) brain scans after CI with a removable magnet. Methods Three criteria (diagnostic usefulness, image quality, artifacts) were assessed at 1.5T and 3T in five cadaver heads with CI. The brain magnetic resonance scans were performed with and without the magnet in situ. The criteria were analyzed by two blinded neuroradiologists, with focus on image distortion and limitation of the diagnostic value of the acquired MR images. Results MR images with the magnet in situ were all compromised by artifacts caused by the CI. After removal of the magnet, MR scans showed an unequivocal artifact reduction with significant improvement of the image quality and diagnostic usefulness, both at 1.5T and 3T. Visibility of the brain stem, cerebellopontine angle, and parieto-occipital lobe ipsilateral to the CI increased significantly after magnet removal. Conclusions The results indicate the possible advantages for 1.5T and 3T MR scanning of the brain in CI carriers with removable magnets. Our findings support use of CIs with removable magnets, especially in patients with chronic intracranial pathologies.

Population Statistics Approach for Safety Assessment in Robotic Cochlear Implantation.

HYPOTHESIS Descriptive statistics with respect to patient anatomy and image guidance accuracy can be used to assess the effectiveness of any system for minimally invasive cochlear implantation, on both an individual patient and wider population level. BACKGROUND Minimally invasive cochlear implantation involves the drilling of a tunnel from the surface of the mastoid to cochlea, with the trajectory passing through the facial recess. The facial recess anatomy constrains the drilling path and places prohibitive accuracy requirements on the used system. Existing single thresholds are insufficient for assessing the effectiveness of these systems. METHODS A statistical model of the anatomical situation encountered during minimally invasive drilling of the mastoid for cochlear implantation was developed. A literature review was performed to determine the statistical distribution of facial recess width; these values were confirmed through facial recess measurements on computed tomography (CT) data. Based on the accuracy of a robotic system developed by the authors, the effect of variation of system accuracy, precision, and tunnel diameter examined with respect to the potential treatable portion of the population. RESULTS A facial recess diameter of 2.54 ± 0.51 mm (n = 74) was determined from a review of existing literature; subsequent measurements on CT data revealed a facial recess diameter of 2.54 ± 0.5 mm (n = 23). The developed model demonstrated the effects of varying accuracy on the treatable portion of the population. CONCLUSIONS The presented model allows the assessment of the applicability of a system on a wider population scale beyond examining only the systems ability to reach an arbitrary threshold accuracy.

Speech Intelligibility in Noise With a Pinna Effect Imitating Cochlear Implant Processor.

Objective: To evaluate the speech intelligibility in noise with a new cochlear implant (CI) processor that uses a pinna effect imitating directional microphone system. Study Design: Prospective experimental study. Setting: Tertiary referral center. Patients: Ten experienced, unilateral CI recipients with bilateral severe-to-profound hearing loss. Intervention: All participants performed speech in noise tests with the Opus 2 processor (omnidirectional microphone mode only) and the newer Sonnet processor (omnidirectional and directional microphone mode). Main Outcome Measure: The speech reception threshold (SRT) in noise was measured in four spatial settings. The test sentences were always presented from the front. The noise was arriving either from the front (S0N0), the ipsilateral side of the CI (S0NIL), the contralateral side of the CI (S0NCL), or the back (S0N180). Results: The directional mode improved the SRTs by 3.6 dB (p < 0.01), 2.2 dB (p < 0.01), and 1.3 dB (p < 0.05) in the S0N180, S0NIL, and S0NCL situations, when compared with the Sonnet in the omnidirectional mode. There was no statistically significant difference in the S0N0 situation. No differences between the Opus 2 and the Sonnet in the omnidirectional mode were observed. Conclusion: Speech intelligibility with the Sonnet system was statistically different to speech recognition with the Opus 2 system suggesting that CI users might profit from the pinna effect imitating directionality mode in noisy environments.

Benefit of a Contralateral Routing of Signal Device for Unilateral Cochlear Implant Users.

Objective: To investigate objective and subjective effects of an adjunctive contralateral routing of signal (CROS) device at the untreated ear in patients with a unilateral cochlear implant (CI). Design: Prospective study of 10 adult experienced unilateral CI users with bilateral severe-to-profound hearing loss. Speech in noise reception (SNR) and sound localization were measured with and without the additional CROS device. SNR was measured by applying speech signals at the untreated/CROS side while noise signals came from the front (S90N0). For S0N90, signal sources were switched. Sound localization was measured in a 12-loudspeaker full circle setup. To evaluate the subjective benefit, patients tried the device for 2 weeks at home, then filled out the abbreviated Speech, Spatial and Qualities of Hearing Scale as well as the Bern benefit in single-sided deafness questionnaires. Results: In the setting S90N0, all patients showed a highly significant SNR improvement when wearing the additional CROS device (mean 6.4 dB, p < 0.001). In the unfavorable setting S0N90, only a minor deterioration of speech understanding was noted (mean -0.66 dB, p = 0.54). Sound localization did not improve substantially with CROS. In the two questionnaires, 12 of 14 items showed an improvement in mean values, but none of them was statistically significant. Conclusion: Patients with unilateral CI benefit from a contralateral CROS device, particularly in a noisy environment, when speech comes from the CROS ear side.

Cochleovestibular Deficit as First Manifestation of Syphilis in a HIV-Infected Patient.

We report the detailed documented case of a 57-year-old homosexual HIV-positive man with bilateral cochleovestibular deficits as a first symptom of syphilis infection in early stage II disease. As a morphological substrate, a strong enhancement of both inner ears and vestibulocochlear nerves were found on gadolinium-enhanced MR scans. The serological tests identified an active infection with Treponema pallidum. After a high-dose treatment with penicillin G and prednisolone, the auditory and vestibular functions and the MR morphology of the vestibulocochlear nerves and inner ears on both sides returned to normal.

Directional Microphone Contralateral Routing of Signals in Cochlear Implant Users: A Within-Subjects Comparison

Objectives: For medical or financial reasons, bilateral cochlear implantation is not always possible in bilaterally deafened patients. In such cases, a contralateral routing of signals (CROS) device could complement the monaural implant. The goal of our study was to compare the benefit of three different conditions: (1) unilateral cochlear implant (CI) alone, (2) unilateral CI complemented with a directional CROS microphone, and (3) bilateral CIs. Design: Twelve bilateral experienced CI users were tested. Speech reception in noise and sound localization were measured in the three above-mentioned conditions. Patients evaluated which condition they presumed to be activated and the subjective benefit on a hearing scale. Results: Compared with the unilateral CI condition, the additional CROS device provided significantly better speech intelligibility in noise when speech signals came from the front or side of the CROS microphone. Only small subjective improvement was observed. Bilateral-activated CIs further improved the hearing performance. This was the only condition where sound localization was possible. Subjective evaluation showed a clear preference for the bilateral CI treatment. Conclusions: In bilateral deafened patients, bilateral implantation is the most preferable form of treatment. However, patients with one implant only could benefit from an additional directional microphone CROS device.

Cochlear Implant Insertion Depth Prediction

HYPOTHESIS The aim of this study was to present and validate the accuracy of a method to predict the required cochlear implant (CI) electrode array length for a specific angular insertion depth (AID). BACKGROUND The human cochlea exhibits remarkable interindividual morphological differences. The prediction of the required array length for a specific AID can help to improve the outcome of cochlear implant surgery. METHODS We estimated the linear insertion depth required for an angular insertion of 540 degrees using computed tomography images of 16 temporal bone specimens (eight Thiel fixed, eight formalin fixed). Free fitting electrode arrays were marked accordingly and inserted through a custom-made insertion guide tube. The achieved AIDs were assessed using postoperative micro-computed tomography scans. RESULTS In the Thiel specimens, the difference between the aimed depth of 540 degrees and achieved insertion depth was small (average 529 degrees, p = 0.076), with a mean prediction error of -11 degrees (maximum 30 degrees), indicating a small underestimation. By contrast, we observed early resistance during the insertions in the formalin specimens (average 409 degrees, p < 0.0001), resulting in a mean error of -131 degrees and bending of the electrode array in the cochlear basal turn in four of eight specimens. CONCLUSION The equation presented in this study for calculating linear insertion depths can be helpful for the selection of adequate electrode array lengths in a clinical setting. The Thiel conservation is a highly suitable model for cadaveric electrode insertion studies. A free online calculator is available at http://www.hno.insel.ch/de/forschung/ci_estimator/.

Functional magnetic resonance imaging in seven borderline cochlear implant candidates: a preliminary research study.

The indications for cochlear implants (CIs) are constantly expanding, as are the numbers of patients who are not ideal or classical CI candidates. For these patients, a careful decision-making process is needed to minimize the risk of poor outcomes. Preoperatively, it may be unclear whether they will benefit from an implantation. As conventionally performed hearing tests (i.e. subjective and electrophysiological examinations, stapedial reflex testing) have limitations, further objective and effective methods for assessment of the central auditory pathway (CAP) are required [1-3]. This article is protected by copyright. All rights reserved.

Paediatric traffic accident and obstructive sleep apnoea by antrochoanal polyps: Case report and literature review

Antrochoanal polyps are hyperplasias of the nasal mucosa, which have their origin in the maxillary sinus and extend through the nasal cavity and the choanae into the naso- and oropharynx. In children antrochoanal polyps represent one of the more frequent manifestations of paediatric nasal polyposis. Most studies on antrochoanal polyps in children report only on nasal obstruction, hyponasal speech and snoring, which are also encountered in the most common cause of obstructive sleep apnoea syndrome; i.e. adenoid or tonsillar hyperplasia. Only very few studies report on additional health hazards by antrochoanal polyps ranging from obstructive sleep apnoea syndrome to swallowing disorders and cachexia. We present the case of an 8 year old girl with a bicycle accident caused by excessive daytime sleepiness and obstructive sleep apnoea syndrome due to an extensive antrochoanal polyp. After a transnasal polypectomy and meatotomy type II the obstructive sleep apnoea and day time sleepiness resolved completely. Awareness of this additional health hazard is important and correct evaluation and timely diagnosis of a potential antrochoanal polyp is mandatory because minimally invasive rhinosurgery is highly curative in preventing further impending problems.