OCT-based intra-cochlear imaging and 3D reconstruction: ex vivo validation of a robotic platform

PURPOSE

The small size of the cochlea, and its location deeply embedded in thick temporal bone, poses a challenge for intra-cochlear guidance and diagnostics. Current radiological imaging techniques are not able to visualize the cochlear microstructures in detail. Rotational optical coherence tomography (OCT) fibers show great potential for intra-cochlear guidance. The generated images could be used to map, and study, the tiny cochlear microstructures relevant for hearing.

METHODS

This work describes the design of a rotational OCT probe with an outer diameter of 0.9 mm. It further discusses a robotic system, which features a remote center of motion mechanism, dedicated to the probe's positioning, fine manipulation and stable insertion into the cochlear micro-spaces. Furthermore, the necessary calibration steps for 3D reconstruction are described, followed by a detailed quantitative analysis, comparing the 3D reconstructions using a synthetic, 2:1 scaled scala tympani model with a reconstruction from micro-CT, serving as the ground truth. Finally, the potential of the system is demonstrated by scanning a single ex vivo cadaveric human cochlea.

RESULTS

The study investigates five insertions in the same 2:1 scaled tympani model, along with their corresponding 3D reconstruction. The comparison with micro-CT results in an average root-mean-square error of 74.2 µm, a signed distance error of 38.1 µm and a standard deviation of 63.6 µm. The average F-score of the reconstructions, using a distance threshold of 100 and 74.2 µm, resulted in 83.0% and 71.8%, respectively. Insertion in the cadaveric human cochlea showed the challenges for straight insertion, i.e., navigating the hook region.

CONCLUSION

Overall, the system shows great potential for intra-cochlear guidance and diagnostics, due to the system's capability for precise and stable insertion into the basal turn in the scala tympani. The system, combined with the calibration procedure, results in detailed and precise 3D reconstructions.

Intracochlear Trauma and Local Ossification Patterns Differ Between Straight and Precurved Cochlear Implant Electrodes

HYPOTHESIS

Trauma to the osseous spiral lamina (OSL) or spiral ligament (SL) during cochlear implant (CI) insertion segregates with electrode type and induces localized intracochlear ossification and fibrosis.

BACKGROUND

The goal of atraumatic CI insertion is to preserve intracochlear structures, limit reactive intracochlear tissue formation, and preserve residual hearing. Previous qualitative studies hypothesized a localized effect of trauma on intracochlear tissue formation; however, quantitative studies failed to confirm this.

METHODS

Insertional trauma beyond the immediate insertion site was histologically assessed in 21 human temporal bones with a CI. Three-dimensional reconstructions were generated and virtually resectioned perpendicular to the cochlear spiral at high resolution. The cochlear volume occupied by ossification or fibrosis was determined at the midpoint of the trauma and compared with regions proximal and distal to this point.

RESULTS

Seven cases, all implanted with precurved electrodes, showed an OSL fracture beyond the immediate insertion site. Significantly more intracochlear ossification was observed at the midpoint of the OSL fracture, compared with the -26 to -18 degrees proximal and 28 to 56 degrees distal to the center. No such pattern was observed for fibrosis. In the 12 cases with a perforation of the SL (9 straight and 3 precurved electrodes), no localized pattern of ossification or fibrosis was observed around these perforations.

CONCLUSION

OSL fractures were observed exclusively with precurved electrodes in this study and may serve as a nidus for localized intracochlear ossification. Perforation of the SL, in contrast, predominantly occurred with straight electrodes and was not associated with localized ossification.

Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion

OBJECTIVES

Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques.

METHODS

One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification.

RESULTS

The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%-44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9).

CONCLUSIONS

Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction.

LEVEL OF EVIDENCE

4: Case-control study Laryngoscope, 134:945-953, 2024.

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.

Interaural and sex differences in the natural evolution of hearing levels in pre-symptomatic and symptomatic carriers of the p.Pro51Ser variant in the COCH gene

Hearing impairment constitutes a significant health problem in developed countries. If hearing loss is slowly progressive, the first signs may not be noticed in time, or remain untreated until the moment the auditory dysfunction becomes more apparent. The present study will focus on DFNA9, an autosomal dominant disorder caused by pathogenic variants in the COCH gene. Although several cross-sectional studies on this topic have been conducted, a crucial need for longitudinal research has been reported by many authors. Longitudinal trajectories of individual hearing thresholds were established as function of age and superimposed lowess curves were generated for 101 female and male carriers of the p.Pro51Ser variant. The average number of times patients have been tested was 2.49 years with a minimum of 1 year and a maximum of 4 years. In addition, interaural and sex differences were studied, as they could modify the natural evolution of the hearing function. The current study demonstrates that, both in female carriers and male carriers, the first signs of hearing decline, i.e. hearing thresholds of 20 dB HL, become apparent as early as the 3rd decade in the highest frequencies. In addition, a rapid progression of SNHL occurs between 40 and 50 years of age. Differences between male and female carriers in the progression of hearing loss are most obvious between the age of 50 and 65 years. Furthermore, interaural discrepancies also manifest from the age of 50 years onwards. High-quality prospective data on the long-term natural evolution of hearing levels offer the opportunity to identify different disease stages in each cochlea and different types of evolution. This will provide more insights in the window of opportunity for future therapeutic intervention trials.

Lumped element models of sound conduction in the human ear: A systematic review

Lumped element models facilitate investigating the fundamental mechanisms of human ear sound conduction. This systematic review aims to guide researchers to the optimal model for the investigated parameters. For this purpose, the literature was reviewed up to 12 July 2023, according to the PRISMA guidelines. Seven models are included via database searching, and another 19 via cross-referencing. The quality of the models is assessed by comparing the predicted middle ear transfer function, the tympanic membrane impedance, the energy reflectance, and the intracochlear pressures (ICPs) (scala vestibuli, scala tympani, and differential) with experimental data. Regarding air conduction (AC), the models characterize the pathway from the outer to the inner ear and accurately predict all six aforementioned parameters. This contrasts with the few existing bone conduction (BC) models that simulate only a part of the ear. In addition, these models excel at predicting one observable parameter, namely, ICP. Thus, a model that simulates BC from the coupling site to the inner ear is still lacking and would increase insights into the human ear sound conduction. Last, this review provides insights and recommendations to determine the appropriate model for AC and BC implants, which is highly relevant for future clinical applications.

Electro-vibrational stimulation results in improved speech perception in noise for cochlear implant users with bilateral residual hearing

A cochlear implant is a neuroprosthetic device that can restore speech perception for people with severe to profound hearing loss. Because of recent evolutions, a growing number of people with a cochlear implant have useful residual acoustic hearing. While combined electro-acoustic stimulation has been shown to improve speech perception for this group of people, some studies report limited adoption rates. Here, we present electro-vibrational stimulation as an alternative combined stimulation strategy that similarly targets the full cochlear reserve. This novel strategy combines the electrical stimulation by the cochlear implant with low-frequency bone conduction stimulation. In a first evaluation of electro-vibrational stimulation, speech perception in noise was assessed in 9 subjects with a CI and symmetrical residual hearing. We demonstrate a statistically significant and clinically relevant improvement for speech perception in noise of 1.9 dB signal-to-noise ratio. This effect was observed with a first prototype that provides vibrational stimulation to both ears with limited transcranial attenuation. Future integration of electro-vibrational stimulation into one single implantable device could ultimately allow cochlear implant users to benefit from their low-frequency residual hearing without the need for an additional insert earphone.

Sulfobetaine-based ultrathin coatings as effective antifouling layers for implantable neuroprosthetic devices

Foreign body response (FBR), inflammation, and fibrotic encapsulation of neural implants remain major problems affecting the impedance of the electrode-tissue interface and altering the device performance. Adhesion of proteins and cells (e.g., pro-inflammatory macrophages, and fibroblasts) triggers the FBR cascade and can be diminished by applying antifouling coatings onto the implanted devices. In this paper, we report the deposition and characterization of a thin (±6 nm) sulfobetaine-based coating onto microfabricated platinum electrodes and cochlear implant (CI) electrode arrays. We found that this coating has stable cell and protein-repellent properties, for at least 31 days in vitro, not affected by electrical stimulation protocols. Additionally, its effect on the electrochemical properties relevant to stimulation (i.e., impedance, charge injection capacity) was negligible. When applied to clinical CI electrode arrays, the film was successful at inhibiting fibroblast adhesion on both the silicone packaging and the platinum/iridium electrodes. In vitro, in fibroblast cultures, coated CI electrode arrays maintained impedance values up to five times lower compared to non-coated devices. Our studies demonstrate that such thin sulfobetaine containing layers are stable and prevent protein and cell adhesion in vitro and are compatible for use on CI electrode arrays. Future in vivo studies should be conducted to investigate its ability to mitigate biofouling, fibrosis, and the resulting impedance changes upon long-term implantation in vivo.

Anatomically and mechanically accurate scala tympani model for electrode insertion studies

The risk of insertion trauma in cochlear implantation is determined by the interplay between individual cochlear anatomy and electrode insertion mechanics. Whereas patient anatomy cannot be changed, new surgical techniques, devices for cochlear monitoring, drugs, and electrode array designs are continuously being developed and tested, to optimize the insertion mechanics and prevent trauma. Preclinical testing of these developments is a crucial step in feasibility testing and optimization for clinical application. Human cadaveric specimens allow for the best simulation of an intraoperative setting. However, their availability is limited and it is not possible to conduct repeated, controlled experiments on the same sample. A variety of artificial cochlear models have been developed for electrode insertion studies, but none of them were both anatomically and mechanically representative for surgical insertion into an individual cochlea. In this study, we developed anatomically representative models of the scala tympani for surgical insertion through the round window, based on microCT images of individual human cochleae. The models were produced in transparent material using commonly-available 3D printing technology at a desired scale. The anatomical and mechanical accuracy of the produced models was validated by comparison with human cadaveric cochleae. Mechanical evaluation was performed by recording insertion forces, counting the number of inserted electrodes and grading tactile feedback during manual insertion of a straight electrode by experienced cochlear implant surgeons. Our results demonstrated that the developed models were highly representative for the anatomy of the original cochleae and for the insertion mechanics in human cadaveric cochleae. The individual anatomy of the produced models had a significant impact on the insertion mechanics. The described models have a promising potential to accelerate preclinical development and testing of atraumatic insertion techniques, reducing the need for human cadaveric material. In addition, realistic models of the cochlea can be used for surgical training and preoperative planning of patient-tailored cochlear implantation surgery.

Three-dimensional quantification of fibrosis and ossification after cochlear implantation via virtual re-sectioning: Potential implications for residual hearing

Hearing preservation may be achieved initially in the majority of patients after cochlear implantation, however, a significant proportion of these patients experience delayed hearing loss months or years later. A prior histological report in a case of delayed hearing loss suggested a potential cochlear mechanical origin of this hearing loss due to tissue fibrosis, and older case series highlight the frequent findings of post-implantation fibrosis and neoosteogenesis though without a focus on the impact on residual hearing. Here we present the largest series (N = 20) of 3-dimensionally reconstructed cochleae based on digitally scanned histologic sections from patients who were implanted during their lifetime. All patients were implanted with multichannel electrodes via a cochleostomy or an extended round window insertion. A quantified analysis of intracochlear tissue formation was carried out via virtual re-sectioning orthogonal to the cochlear spiral. Intracochlear tissue formation was present in every case. On average 33% (SD 14%) of the total cochlear volume was occupied by new tissue formation, consisting of 26% (SD 12%) fibrous and 7% (SD 6%) bony tissue. The round window was completely covered by fibro-osseous tissue in 85% of cases and was associated with an obstruction of the cochlear aqueduct in 100%. The basal part of the basilar membrane was at least partially abutted by the electrode or new tissue formation in every case, while the apical region, corresponding with a characteristic frequency of < 500 Hz, appeared normal in 89%. This quantitative analysis shows that after cochlear implantation via extended round window or cochleostomy, intracochlear fibrosis and neoossification are present in all cases at anatomical locations that could impact normal inner ear mechanics.

Measures of Speech Understanding in Noise for Young Children with a Cochlear Implant in Mainstream and Special Education

The use of two types of speech-in-noise (SPIN) assessment, namely digits-in-noise self-tests and open-set, monosyllabic word tests, to assess the SPIN understanding performance of children with cochlear implants (CI) in mainstream and special education, was investigated. The tests' feasibility and reliability and the influence of specific cognitive abilities on their results were studied. The results of 30 children with CIs in mainstream and special education were compared to those of 60 normal-hearing children in elementary school. Results indicate that the digit triplet test (DTT) was feasible for all children tested in this study, as seen by the familiarity of all the digits, the high stability of the test results (<3 dB SNR), and a small measurement error (≤2 dB SNR). Remembering full triplets did not form a problem and results did not show systematic attention loss. For children with CIs, the performance on the DTT was strongly related to the performance on the open-set monosyllabic word-in-noise task. However, small but significant differences were observed in the performance of children with CIs in mainstream and special education on the monosyllabic word test. Both tests showed little influence of cognitive abilities, making them both useful in situations where the bottom-up auditory aspect of SPIN performance needs to be investigated or in situations where sentence-in-noise tests are too challenging.

An optically-guided cochlear implant sheath for real-time monitoring of electrode insertion into the human cochlea

In cochlear implant surgery, insertion of perimodiolar electrode arrays into the scala tympani can be complicated by trauma or even accidental translocation of the electrode array within the cochlea. In patients with partial hearing loss, cochlear trauma can not only negatively affect implant performance, but also reduce residual hearing function. These events have been related to suboptimal positioning of the cochlear implant electrode array with respect to critical cochlear walls of the scala tympani (modiolar wall, osseous spiral lamina and basilar membrane). Currently, the position of the electrode array in relation to these walls cannot be assessed during the insertion and the surgeon depends on tactile feedback, which is unreliable and often comes too late. This study presents an image-guided cochlear implant device with an integrated, fiber-optic imaging probe that provides real-time feedback using optical coherence tomography during insertion into the human cochlea. This novel device enables the surgeon to accurately detect and identify the cochlear walls ahead and to adjust the insertion trajectory, avoiding collision and trauma. The functionality of this prototype has been demonstrated in a series of insertion experiments, conducted by experienced cochlear implant surgeons on fresh-frozen human cadaveric cochleae.

Otomicroscopic and functional outcomes after cleft palate repair via Sommerlad intravelar veloplasty vs. modified Veau-Wardill-Kilner push-back

OBJECTIVE

We aim to compare the modified Veau-Wardill-Kilner push-back technique (VWK) and the Sommerlad intravelar veloplasty (Sommerlad IVVP) in terms of middle ear outcomes and oronasal fistulae frequency in three years old children.

METHODS

For this retrospective cohort study, data were collected and anonymized from consecutive patients with cleft palate (with or without cleft lip) who underwent surgery in our hospital between January 2008 and December 2018. Patients with syndromic diagnoses and patients who underwent surgical treatment elsewhere were excluded. We collected data from 101 children (202 ears) regarding middle ear complications at the age of three, including acute otitis media, middle ear effusion, tympanic membrane retraction, tympanic membrane perforation, tympanic membrane atelectasis and chronic otitis media with cholesteatoma. In addition, the presence of oronasal fistulae and the number of ventilation tubes received by the age of three were recorded.

RESULTS

The odds of children having a normal middle ear evaluation were 3.07 (95% Confidence interval (95%CI): [1.52, 6.12]; p < 0.05) times higher when children received Sommerlad IVVP compared to modified VWK. With 40.7% compared to 26.7%, a significantly higher incidence of middle ear effusion was present in the modified VWK group compared to Sommerlad IVVP (X²(1) = 4.38, p < 0.05). Furthermore, this group needed significantly more ventilation tube reinsertions (X²(2) = 12.22, p < 0.05) and was found to have a significantly higher incidence of oronasal fistula (53.5% vs. 17.2%, X²(1) = 14.75, p < 0.05). The latter was significantly associated with a higher need for ventilation tube reinsertion (X²(1) = 7.34, p < 0.05).

CONCLUSION

This study shows superior middle ear outcomes and fewer oronasal fistulae after Sommerlad IVVP compared to modified Veau-Wardill-Kilner push-back at the age of three.

Fear influences phantom sound percepts in an anechoic room

Aims and hypotheses

In an environment of absolute silence, researchers have found many of their participants to perceive phantom sounds (tinnitus). With this between-subject experiment, we aimed to elaborate on these research findings, and specifically investigated whether–in line with the fear-avoidance model of tinnitus perception and reactivity–fear or level of perceived threat influences the incidence and perceptual qualities of phantom sound percepts in an anechoic room. We investigated the potential role of individual differences in anxiety, negative affect, noise sensitivity and subclinical hearing loss. We hypothesized that participants who experience a higher level of threat would direct their attention more to the auditory system, leading to the perception of tinnitus-like sounds, which would otherwise be subaudible, and that under conditions of increased threat, narrowing of attention would lead to perceptual distortions.

Methods

In total, N = 78 normal-hearing volunteers participated in this study. In general, the study sample consisted of young, mostly female, university students. Their hearing was evaluated using gold-standard pure tone audiometry and a speech-in-noise self-test (Digit Triplet Test), which is a sensitive screening test to identify subclinical hearing loss. Prior to a four-minute stay in an anechoic room, we randomized participants block design-wise in a threat (N = 37) and no-threat condition (N = 41). Participants in the threat condition were deceived about their hearing and were led to believe that staying in the room would potentially harm their hearing temporarily. Participants were asked whether they perceived sounds during their stay in the room and rated the perceptual qualities of sound percepts (loudness and unpleasantness). They were also asked to fill-out standardized questionnaires measuring anxiety (State–Trait Anxiety Inventory), affect (Positive and Negative Affect Schedule) and noise sensitivity (Weinstein Noise Sensitivity Scale). The internal consistency of the questionnaires used was verified in our study sample and ranged between α = 0.61 and α = 0.90.

Results

In line with incidence rates reported in the literature, 74% of our participants reported having heard tinnitus-like sounds in the anechoic room. Speech-in-noise identification ability was comparable for both groups of participants. The experimental manipulation of threat was proven to be effective, as indicated by significantly higher scores on a Threat Manipulation Checklist among participants in the threat condition as compared to those in the no-threat condition (p < 0.01). Nevertheless, participants in the threat condition were as likely to report tinnitus percepts as participants in the no-threat condition (p = 1), and tinnitus percepts were not rated as being louder (p = 0.76) or more unpleasant (p = 0.64) as a function of level of threat. For participants who did experience tinnitus percepts, a higher level of threat was associated with a higher degree of experienced unpleasantness (p < 0.01). These associations were absent in those who did not experience tinnitus. Higher negative affect was only slightly associated with higher ratings of tinnitus unpleasantness (p < 0.01).

Conclusion

Whereas our threat manipulation was successful in elevating the level of fear, it did not contribute to a higher percentage of participants perceiving tinnitus-like sounds in the threat condition. However, higher levels of perceived threat were related to a higher degree of perceived tinnitus unpleasantness. The findings of our study are drawn from a rather homogenous participant pool in terms of age, gender, and educational background, challenging conclusions that are applicable for the general population. Participants generally obtained normophoric scores on independent variables of interest: they were low anxious, low noise-sensitive, and there was little evidence for the presence of subclinical hearing loss. Possibly, there was insufficient variation in scores to find effects.

Intracochlear pressure as an objective measure for perceived loudness with bone conduction implants

BACKGROUND

The generally accepted method to assess the functionality of novel bone conduction implants in a preclinical stage is to experimentally measure the vibratory response of the cochlear promontory. Yet, bone conduction of sound is a complex propagation phenomenon, depending on both frequency and amplitude, involving different conduction pathways.

OBJECTIVES

The aim of this study is to validate the use of intracochlear sound pressure (ICP) as an objective indicator for perceived loudness for bone conduction stimulation. It is investigated whether a correlation exists between intracochlear sound pressure measurements in cadaveric temporal bones and clinically obtained results using the outcome of a loudness balancing experiment.

METHODS

Ten normal hearing subjects were asked to balance the perceived loudness between air conducted (AC) sound and bone conducted (BC) sound by changing the AC stimulus. Mean balanced thresholds were calculated and used as stimulation levels in a cadaver trial (N = 4) where intracochlear sound pressure was measured during AC and BC stimulation to assess the correlation with the measured clinical data. The intracochlear pressure was measured at the relatively low stimulation amplitude of 80 dBHL using a lock-in amplification technique.

RESULTS

Applying AC and BC stimulation at equal perceived loudness on cadaveric heads yield a similar differential intracochlear pressure, with differences between AC and BC falling within the range of variability of normal hearing test subjects.

CONCLUSION

Comparing the perceived loudness at 80 dB HL for both AC and BC validates intracochlear pressure as an objective indicator of the cochlear drive. The measurement setup is more time-intensive than measuring the vibratory response of the cochlear promontory, yet it provides direct information on the level of the cochlear scalae.

Antiviral treatment with fluoxetine for rituximab-associated chronic echovirus 13 meningoencephalitis and myofasciitis

BACKGROUND & PURPOSE

Enterovirus infections pose a serious threat for patients with humoral deficiencies and may be lethal, while the efficacy of proposed treatment options, such as corticosteroids, intravenous immunoglobulins and fluoxetine remain debated.

METHODS

We investigated viral clearance in a patient with rituximab-induced B-cell depletion and chronic echovirus 13 (E13) meningoencephalitis/myofasciitis in response to intravenous immunoglobulins and fluoxetine using sequential semi-quantitative E13 viral load measurements by real-time reverse transcription polymerase chain reaction. Fluoxetine concentrations in plasma and cerebrospinal fluid were determined by liquid chromatography-mass spectrometry.

RESULTS

Intravenous immunoglobulins appeared ineffective in this case of E13 infection, whereas virus clearance in cerebrospinal fluid was obtained after 167 days of oral fluoxetine. Since treatment with corticosteroids resulted in a flare of symptoms, rechallenge with viral load measurements was not attempted.

CONCLUSION

In this report of a patient with rituximab-associated chronic echovirus 13 meningoencephalitis viral clearance in response to single treatment options is assessed for the first time. Our observations further support the in vivo efficacy of fluoxetine against enteroviral infections. More research is needed to establish its efficacy in different enterovirus strains.

Inner Ear Pharmacotherapy for Residual Hearing Preservation in Cochlear Implant Surgery: A Systematic Review

Cochlear implantation initiates an inflammatory cascade in which both acute insertion trauma and chronic foreign body reaction lead to intracochlear fibrosis and loss of residual hearing. Several strategies have been proposed to attenuate the local reactive process after implantation, including intracochlear drug delivery. The present study gives an overview of what is being investigated in the field of inner ear therapeutics and cochlear implant surgery. The aim is to evaluate its potential benefit in clinical practice. A systematic search was conducted in PubMed, Embase, and Cochrane Library databases identifying comparative prospective studies examining the effect of direct inner ear drug application on mechanical cochlear trauma. Both animal and human studies were considered and all studies were assessed for quality according to the validated risk of bias tools. Intracochlear administration of drugs is a feasible method to reduce the local inflammatory reaction following cochlear implantation. In animal studies, corticosteroid use had a significant effect on outcome measures including auditory brainstem response, impedance, and histological changes. This effect was, however, only durable with prolonged drug delivery. Significant differences in outcome were predominantly seen in studies where the cochlear damage was extensive. Six additional reports assessing non-steroidal agents were found. Overall, evidence of anti-inflammatory effects in humans is still scarce.

Unification of Treatments and Interventions for Tinnitus Patients (UNITI): a study protocol for a multi-center randomized clinical trial

BACKGROUND

Tinnitus represents a relatively common condition in the global population accompanied by various comorbidities and severe burden in many cases. Nevertheless, there is currently no general treatment or cure, presumable due to the heterogeneity of tinnitus with its wide variety of etiologies and tinnitus phenotypes. Hence, most treatment studies merely demonstrated improvement in a subgroup of tinnitus patients. The majority of studies are characterized by small sample sizes, unstandardized treatments and assessments, or applications of interventions targeting only a single organ level. Combinatory treatment approaches, potentially targeting multiple systems as well as treatment personalization, might provide remedy and enhance treatment responses. The aim of the present study is to systematically examine established tinnitus therapies both alone and in combination in a large sample of tinnitus patients. Further, it wants to provide the basis for personalized treatment approaches by evaluating a specific decision support system developed as part of an EU-funded collaborative project (Unification of treatments and interventions for tinnitus patients; UNITI project).

METHODS/STUDY DESIGN

This is a multi-center parallel-arm randomized clinical trial conducted at five different clinical sites over the EU. The effect of four different tinnitus therapy approaches (sound therapy, structured counseling, hearing aids, cognitive behavioral therapy) applied over a time period of 12 weeks as a single or rather a combinatory treatment in a total number of 500 chronic tinnitus patients will be investigated. Assessments and interventions are harmonized over the involved clinical sites. The primary outcome measure focuses on the domain tinnitus distress assessed via the Tinnitus Handicap Inventory.

DISCUSSION

Results and conclusions from the current study might not only provide an essential contribution to combinatory and personalized treatment approaches in tinnitus but could also provide more profound insights in the heterogeneity of tinnitus, representing an important step towards a cure for tinnitus.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04663828 . Registered on 11 December 2020.

Prevalence of Otological Disease in Turner Syndrome: A Systematic Review

INTRODUCTION

Girls and women with Turner syndrome (TS) present with multiple ear and hearing problems, ranging from external morphologic abnormalities to sensorineural or conductive hearing loss. The exact pathophysiology behind these otological diseases is not yet completely understood. The aim of this study is to provide a systematic review on the prevalence of otological disease in TS.

METHODS

We conducted a systematic review according to the PRISMA guidelines. A database search was performed in PubMed, Embase, Web of Science, and Cochrane library.

RESULTS

The prevalence of otological disease as external ear deformities (20-62%), recurrent otitis media (24-48%), and hearing loss (36-84%) is high in TS. The auditory phenotype in TS is complex and seems to be dynamic with CHL due to middle ear disease at young age and sensorineural hearing loss later in life.

CONCLUSION

This systematic review of the literature confirms that otological disease is definitely part of the widely variable phenotype in Turner patients. Strong evidence is lacking on the exact prevalence numbers, emphasizing the need for more prospective data gathering. Growing insights in its pathophysiology will help in the understanding and management of hearing problems in TS across lifespan.

Safety of active auditory implants in magnetic resonance imaging

Magnetic resonance imaging (MRI) has become the gold standard for the diagnosis of many pathologies. Using MRI in patients with auditory implants can however raise concerns due to mutual interactions between the implant and imaging device, resulting in potential patient risks. Several implant manufacturers have been working towards more MRI safe devices. Older devices are however often labelled for more stringent conditions, possibly creating confusion with patients and professionals. With this myriad of different devices that are implanted in patients for lifetimes of at least 20 years, it is crucial that both patients and professionals have a clear understanding of the safety of their devices. This work aims at providing an exhaustive overview on the MRI safety of active auditory implants. The available industry standards that are followed by manufacturers are outlined and an overview of the latest scientific developments focusing on the last five years is provided. In addition, based on the analysis of the adverse events reported to the Food and Drug Administration (FDA) and in literature within the past ten years, a systematic review of the most commonly occurring issues for patients with auditory implants in the MRI environment is provided. Results indicate that despite the release of more MRI conditional active hearing implants on the market, adverse events still occur. An extensive overview is provided on the MRI safety of active auditory implants, aiming to increase the understanding of the topic for healthcare professionals and contribute to safer scanning conditions for patients.

Towards a unification of treatments and interventions for tinnitus patients: The EU research and innovation action UNITI

Tinnitus is the perception of a phantom sound and the patient's reaction to it. Although much progress has been made, tinnitus remains a scientific and clinical enigma of high prevalence and high economic burden, with an estimated prevalence of 10%-20% among the adult population. The EU is funding a new collaborative project entitled "Unification of Treatments and Interventions for Tinnitus Patients" (UNITI, grant no. 848261) under its Horizon 2020 framework. The main goal of the UNITI project is to set the ground for a predictive computational model based on existing and longitudinal data attempting to address the question of which treatment or combination of treatments is optimal for a specific patient group based on certain parameters. Clinical, epidemiological, genetic and audiological data, including signals reflecting ear-brain communication, as well as patients' medical history, will be analyzed making use of existing databases. Predictive factors for different patient groups will be extracted and their prognostic relevance validated through a Randomized Clinical Trial (RCT) in which different patient groups will undergo a combination of tinnitus therapies targeting both auditory and central nervous systems. From a scientific point of view, the UNITI project can be summarized into the following research goals: (1) Analysis of existing data: Results of existing clinical studies will be analyzed to identify subgroups of patients with specific treatment responses and to identify systematic differences between the patient groups at the participating clinical centers. (2) Genetic and blood biomarker analysis: High throughput Whole Exome Sequencing (WES) will be performed in well-characterized chronic tinnitus cases, together with Proximity Extension Assays (PEA) for the identification of blood biomarkers for tinnitus. (3) RCT: A total of 500 patients will be recruited at five clinical centers across Europe comparing single treatments against combinational treatments. The four main treatments are Cognitive Behavioral Therapy (CBT), hearing aids, sound stimulation, and structured counseling. The consortium will also make use of e/m-health applications for the treatment and assessment of tinnitus. (4) Decision Support System: An innovative Decision Support System will be implemented, integrating all available parameters (epidemiological, clinical, audiometry, genetics, socioeconomic and medical history) to suggest specific examinations and the optimal intervention strategy based on the collected data. (5) Financial estimation analysis: A cost-effectiveness analysis for the respective interventions will be calculated to investigate the economic effects of the interventions based on quality-adjusted life years. In this paper, we will present the UNITI project, the scientific questions that it aims to address, the research consortium, and the organizational structure.

Electropolymerized Receptor Coatings for the Quantitative Detection of Histamine with a Catheter-Based, Diagnostic Sensor

In this article, we report on the development of a catheter-based, biomimetic sensor as a step toward a minimally invasive diagnostic instrument in the context of functional bowel disorders. Histamine is a key mediator in allergic and inflammatory processes in the small intestines; however, it is a challenge to determine histamine levels at the duodenal mucosa, and classical bioreceptors are unsuitable for use in the digestive medium of bowel fluid. Therefore, we have developed molecularly imprinted polypyrrole coatings for impedimetric sensing electrodes, which enable the quantification of histamine in nondiluted, human bowel fluid in a broad concentration range from 25 nM to 1 μM. The electrodes show negligible cross-sensitivity to histidine as a competitor molecule and, for comparison, we also evaluated the response of nonimprinted and taurine-imprinted polypyrrole to histamine. Furthermore, using equivalent-circuit modeling, we found that the molecular recognition of histamine by polypyrrole primarily increases the resistive component of the electrode-liquid interface while capacitive effects are negligible. The sensor, integrated into a catheter, measures differentially to correct for nonspecific adsorption effects in the complex matrix of bowel fluids, and a single triggering frequency is sufficient to determine histamine concentrations. Together, these features are beneficial for real-time diagnostic tests.

Intratemporal facial nerve schwannomas: multicenter experience of 80 cases

PURPOSE

To provide more data on the clinical presentation and natural evolution of facial nerve schwannomas and to provide guidance for therapeutic decision making.

METHODS

A retrospective case review of eighty patients diagnosed with a facial nerve schwannoma between 1990 and 2018 in ten tertiary referral centers in Europe was performed. Patients' demographics, symptomatology, audiometry, anatomical site (segments involved), size and whenever possible volume measurement were registered.

RESULTS

At presentation, transient or persistent facial palsy was the most common symptom, followed by hearing loss. The schwannoma involved more than one segment in the majority of the patients with the geniculate ganglion being most commonly involved. Initial treatment consisted of a wait and scan approach in 67.5%, surgery in 30% and radiation therapy in 2.5% of the patients. Tympanic segment schwannomas caused mainly conductive hearing loss and were more prone to develop facial palsy at follow-up. Internal auditory canal or cerebellopontine angle schwannomas presented with significantly more sensorineural hearing loss.

CONCLUSIONS

Although modern imaging has improved diagnosis of this tumor, choosing the best treatment modality remains a real challenge. Based on the literature review and current findings, more insights into the clinical course and the management of facial nerve schwannomas are provided.

Stability of the standard incus coupling of the Carina middle ear actuator after 1.5T MRI

Limited data is available concerning the safety of active middle ear implants (AMEI) during Magnetic Resonance Imaging (MRI). Measurements in temporal bones are the gold standard for preclinical assessment of device safety. In this study the coupling stability of an actuator as used in a fully implantable AMEI was determined in temporal bones. Eleven temporal bones were implanted with the actuator according to the manufacturer’s surgical guidelines. The actuator was coupled on the incus short process as recommended for sensorineural hearing loss. Temporal bones were exposed 10 times to the MRI magnetic field by entering the MRI suite in a clinically relevant way. Computed Tomography (CT) images were acquired before and after the experiment to investigate the risk of actuator dislocation. Based on the electrical impedance of the actuator, the loading of the actuator to the incus was confirmed. Relative actuator displacement was determined on the CT images by comparing the initial with the final actuator position in 3D space. Impedance curves were analyzed after each exposure to check the loading of the actuator to the ossicles. Analysis of CT images with a 0.30.6 mm in-plane resolution indicate no actuator displacement. The maximum detected change in impedance for all actuators was 8.43 Ω at the actuator’s resonance frequency. Impedance curves measured when the actuator was retracted from the short process after the experiment still indicate the presence of a clear resonance peak. No actuator displacement or dislocation could be detected in the analysis of CT images and the measured impedance curves. Impedance curves obtained when the actuator was retracted from the incus short process still show a clear resonance peak, indicating the device is still functional after the MRI exposures.

Towards a catheter-based impedimetric sensor for the assessment of intestinal histamine levels in IBS patients

In this work, we report on the development of a catheter-based sensor designed for measuring the concentration of histamine in the human duodenum. Certain gut disorders, such as the irritable bowel syndrome (IBS), are associated with elevated levels of intestinal histamine due to chronic immune activation. As it is still impossible to determine histamine concentrations in vivo, a nasointestinal catheter with histamine-sensing capabilities has the potential to become a valuable diagnostic instrument. Regarding the sensing principle, we selected impedance spectroscopy using voltages that are compatible with intra-body applications with molecularly imprinted polymers (MIPs) as recognition elements. MIPs are synthetic receptors that offer the advantages of robustness, high specificity and selectivity for histamine as a target. In this specific case, the MIPs were synthesized from acryclic acid monomers, which guarantees a uniform binding capacity within the pH range of intestinal fluid. We have validated the catheter sensor on human intestinal liquids spiked with histamine in a testing setup that mimics the environment inside the duodenum. The dose-response curves show an analytical range between 5 and 200 nM of histamine, corresponding to physiologically normal conditions while higher concentrations correlate with disease. The key output signal of the sensor is the resistive component of the MIP-functionalized titanium electrodes as derived from the equivalent-circuit modelling of full-range impedance spectra. Future applications could be catheters tailored to cardiovascular, urological, gastrointestinal, and neurovascular applications. This, in combination with the versatility of the MIPs, will make this sensor platform a versatile diagnostic tool.

Research Insights on Neural Effects of Auditory Deprivation and Restoration in Unilateral Hearing Loss: A Systematic Review

Neuroplasticity following bilateral deafness and auditory restoration has been repeatedly investigated. In clinical practice, however, a significant number of patients present a severe-to-profound unilateral hearing loss (UHL). To date, less is known about the neuroplasticity following monaural hearing deprivation and auditory input restoration. This article provides an overview of the current research insights on the impact of UHL on the brain and the effect of auditory input restoration with a cochlear implant (CI). An exhaustive systematic review of the literature was performed selecting 38 studies that apply different neural analyses techniques. The main results show that the hearing ear becomes functionally dominant after monaural deprivation, reshaping the lateralization of the neural network for auditory processing, a process that can be considered to influence auditory restoration. Furthermore, animal models predict that the onset time of UHL impacts auditory restoration. Hence, the results seem to advocate for early restoration of UHL, although further research is required to disambiguate the effects of duration and onset of UHL on auditory restoration and on structural neuroplasticity following UHL deprivation and restoration. Ongoing developments on CI devices compatible with Magnetic Resonance Imaging (MRI) examinations will provide a unique opportunity to investigate structural and functional neuroplasticity following CI restoration more directly.

Development and validation of a method to record electrophysiological responses in direct acoustic cochlear implant subjects

Acoustic hearing implants, such as direct acoustic cochlear implants (DACIs), can be used to treat profound mixed hearing loss. Electrophysiological responses in DACI subjects are of interest to confirm auditory processing intra-operatively, and to assist DACI fitting postoperatively. We present two related studies, focusing on DACI artifacts and electrophysiological measurements in DACI subjects, respectively. In the first study we aimed to characterize DACI artifacts, to study the feasibility of measuring frequency-specific electrophysiological responses in DACI subjects. Measurements of DACI artifacts were collected in a cadaveric head to disentangle possible DACI artifact sources and compared to a constructed DACI artifact template. It is shown that for moderate stimulation levels, DACI artifacts are mainly dominated by the artifact from the radio frequency (RF) communication signal, that can be modeled if the RF encoding protocol is known. In a second study, the feasibility of measuring intra-operative responses, without applying the RF artifact models, in DACI subjects is investigated. Auditory steady-state and brainstem responses were measured intra-operatively in three DACI subjects, immediately after implantation, to confirm proper DACI functioning and coupling to the inner ear. Intra-operative responses could be measured in two of the three tested subjects. Absence of intra-operative responses in the third subject can possibly be explained by the hearing loss, attenuation of intra-operative responses, the difference between electrophysiological and behavioral threshold, and a temporary threshold shift due to the DACI surgery. In conclusion, RF artifacts can be modeled, such that electrophysiological responses to frequency-specific stimuli could possibly be measured in DACI subjects, and intra-operative responses in DACI subjects can be obtained.

A Role for Acoustic Stimulation in Advanced Otosclerosis: Direct Acoustic Cochlear Implant versus Cochlear Implant

Recent findings support the efficacy of the direct acoustic cochlear implant (DACI) in patients with advanced otosclerosis whose rehabilitation is very challenging. Standard treatment consists of stapes surgery combined with hearing aids or a cochlear implant (CI). CI surgery, however, is often challenging depending on the grade of otosclerosis. This study aims to compare speech perception scores in quiet and noise of 6 DACI and 12 CI patients with advanced otosclerosis at 3 and 12 months after fitting. Preoperative computed tomographic scans of all patients were scored by experts using an existing otosclerosis grading system (stages 1–3). Speech perception in quiet was significantly better for DACI compared to CI users at 3 months after fitting. At 12 months, no difference was found between DACI and CI patients. Speech perception scores in noise were significantly better in the DACI group. In summary, a DACI system seems to provide an effective treatment option as the acoustic component can be preserved in patients with advanced otosclerosis.

Assessment of Ipsilateral Efferent Effects in Human via ECochG

Development of electrophysiological means to assess the medial olivocochlear (MOC) system in humans is important to further our understanding of the function of that system and for the refinement and validation of psychoacoustical and otoacoustic emission methods which are thought to probe the MOC. Based on measurements in anesthetized animals it has been hypothesized that the MOC-reflex (MOCR) can enhance the response to signals in noise, and several lines of evidence support such a role in humans. A difficulty in these studies is the isolation of efferent effects. Efferent activation can be triggered by acoustic stimulation of the contralateral or ipsilateral ear, but ipsilateral stimulation is thought to be more effective. However, ipsilateral stimulation complicates interpretation of effects since these sounds can affect the perception of other ipsilateral sounds by mechanisms not involving olivocochlear efferents. We assessed the ipsilaterally evoked MOCR in human using a transtympanic procedure to record mass-potentials from the cochlear promontory or the niche of the round window. Averaged compound action potential (CAP) responses to masked probe tones of 4 kHz with and without a precursor (designed to activate the MOCR but not the stapedius reflex) were extracted with a polarity alternating paradigm. The masker was either a simultaneous narrow band noise masker or a short (20-ms) tonal ON- or OFF-frequency forward masker. The subjects were screened for normal hearing (audiogram, tympanogram, threshold stapedius reflex) and psychoacoustically tested for the presence of a precursor effect. We observed a clear reduction of CAP amplitude by the precursor, for different masking conditions. Even without an MOCR, this is expected because the precursor will affect the response to subsequent stimuli via neural adaptation. To determine whether the precursor also activated the efferent system, we measured the CAP over a range of masker levels, with or without precursor, and for different types of masker. The results show CAP reduction consistent with the type of gain reduction caused by the MOCR. These results generally support psychoacoustical paradigms designed to probe the efferent system as indeed activating the MOCR system, but not all observations are consistent with this mechanism.

Prevalence and Nature of Hearing Loss in 22q11.2 Deletion Syndrome

PURPOSE

The purpose of this study was to clarify the prevalence, type, severity, and age-dependency of hearing loss in 22q11.2 deletion syndrome.

METHOD

Extensive audiological measurements were conducted in 40 persons with proven 22q11.2 deletion (aged 6-36 years). Besides air and bone conduction thresholds in the frequency range between 0.125 and 8.000 kHz, high-frequency thresholds up to 16.000 kHz were determined and tympanometry, acoustic reflex (AR) measurement, and distortion product otoacoustic emission (DPOAE) testing were performed.

RESULTS

Hearing loss was identified in 59% of the tested ears and was mainly conductive in nature. In addition, a high-frequency sensorineural hearing loss with down-sloping curve was found in the majority of patients. Aberrant tympanometric results were recorded in 39% of the ears. In 85% of ears with a Type A or C tympanometric peak, ARs were absent. A DPOAE response in at least 6 frequencies was present in only 23% of the ears with a hearing threshold ≤30 dB HL. In patients above 14 years of age, there was a significantly lower percentage of measurable DPOAEs.

CONCLUSION

Hearing loss in 22q11.2 deletion syndrome is highly prevalent and both conductive and high-frequency sensorineural in nature. The age-dependent absence of DPOAEs in 22q11.2 deletion syndrome suggests cochlear damage underlying the high-frequency hearing loss.

Predictive factors of speech understanding in adults with cochlear implants

OBJECTIVE

The aim of this study was to analyse the factors that influenced speech recognition scores in quiet conditions and speech reception threshold levels (SRT) in fixed noise conditions, after cochlear implant (CI) surgery in adults with postlinguistic deafness.

STUDY DESIGN

Combined retrospective and prospective study in a tertiary referral centre.

METHODS

We included 66 patients that received implants between 2002 and 2013. We retrospectively collected speech recognition scores and 14 demographic, audiological, and technical factors, including gender, age at implantation, aetiology, hearing loss progression, preoperative Pure Tone Average (PTA), hearing loss onset age and duration, duration and use of hearing aids (HAs); implantation in the best or worst ear; implantation on the right or left side; use of HA after implantation; and the duration and type of CI. We prospectively tested a subgroup of 21 patients for SRT in fixed noise.

RESULTS

The hearing loss duration significantly affected speech recognition scores in quiet conditions (H (4) = 10.567, p =0.032) and SRTs in fixed noise conditions (rs = 0.466, p = 0.033). The PTA of the better ear significantly affected only the SRT in fixed noise conditions (rs = 0.57 1, p = 0.007).

CONCLUSION

The duration of hearing loss and the PTA of the best ear had significant effects on the outcomes of speech recognition and SRT in quiet and fixed noise conditions, respectively. These findings are important for counselling CI candidates. Further studies in larger study populations are warranted.

Speech-in-noise testing as a marker for noise-induced hearing loss and tinnitus

Speech-in-noise testing as a marker for noise-induced hearing loss and tinnitus. Noise-induced hearing loss and tinnitus are auditory complaints that often co-occur. Often, there is no immediate indication of changes in the pure tone audiogram. Patients can still have clinically normal hearing thresholds while clearly experiencing reduced speech comprehension. This might be explained by the process of neurodegeneration of the innervated dendrites of the auditory nerve fibres and secondary degeneration of spiral ganglion neurons. Subsequent maladaptive neuronal plasticity of the central auditory system can induce tinnitus. Standard hearing testing is no longer sufficient in these patients. Therefore more complex tasks, such as speech-in-noise tests, might be valuable extensions to the standard hearing tests. We carried out a prospective investigation of the influence of tinnitus upon speech comprehension in noise and the effectiveness of speech-in-noise testing, using the Flemish version of the digit triplet test (DTT). Thirty-seven patients with mild noise-induced hearing loss, tinnitus complaints and clinically normal pure tone thresholds completed the DTT and filled in two tinnitus enquiries. A statistically significant (p=0.026) correlation between the averaged high PTA, 2,z and the averaged SRT across ears on the DTT was found. There also seems to be a slight influence of tinnitus onset on the SRT score.

Otosclerosis: Shift in bone conduction after stapedotomy

OBJECTIVES

To analyze changes in bone conduction (BC) thresholds before and after stapedotomy in patients with clinical otosclerosis with a focus on the Carhart notch, which is defined as a significant loss of BC at a certain audiometric frequency.

METHODOLOGY

Retrospective case review of pure tone audiometry (PTA) in 213 patients who underwent a stapedotomy at a tertiary referral center between 2004 and 2011. The patients were grouped by age and the frequency of the Carhart notch. The non-operated ear was also evaluated.

RESULTS

The Carhart notch was present on pre-operative audiometry in 158 (74%) patients at 0.5 (n = 18, 8.45%), 1 (n = 25, 11.70%), or 2 kHz (n = 115, 54.0%). We measured a mean postoperative improvement in BC of 7.5, 8.4, and 8.8 dB HL. Pre-operatively, 55 (25.8%) patients did not exhibit a typical notch configuration. The mean gain in BC, defined on PTA according to the AAO-HNS criteria (0.5, 1, 2 and 3, or 4 kHz), was 1.8 dB HL after stapedotomy.

CONCLUSION

The Carhart notch was not solely related to the 2 kHz frequency. The greatest gain in BC after stapedotomy for otosclerosis occurred at the notch frequency.

Aetiology of congenital hearing loss: a cohort review of 569 subjects

OBJECTIVE

Newborn hearing screening was implemented in Flanders about fifteen years ago. The aim of this study was to determine the aetiology of hearing loss detected by the Flemish screening programme.

METHODS

From 1997 to 2011, 569 neonates were referred to our tertiary referral centre after failed neonatal screening with Auditory Brainstem Responses. In case hearing loss (HL) was confirmed, further diagnostic testing was launched. A retrospective chart review was performed analysing the degree of HL, risk factor and aetiology.

RESULTS

Metabolic disorders (0.5%), infectious diseases (35.8%), congenital malformations (6.1%) and genetic abnormalities (19.8%), whether or not syndromic, were retained. In 35% of the subjects no obvious aetiology could be determined in the current study.

CONCLUSION

In contrast to the literature findings, this series shows a genetic syndromic cause in 80% of the genetic bilateral HL cases. On the other hand connexin positive diagnoses were mostly underrepresented in this study, showing the need for better screening.

Noise exposure of care providers during otosurgical procedures

OBJECTIVE

To monitor the noise exposure of care providers during otological surgery due to drilling and suction in the operating room.

METHODS

A clinical study monitoring different standard otosurgical procedures was conducted; cochlear implantation (CI), mastotympanoplasty, and mastoidectomy alone. Noise exposure to the surgeon and assistant were monitored with wireless personal noise dosimetry and stationary sound monitoring. Both maximum peak level in dBC (Lpeak) and time-average sound pressure level in dBA (equivalent level or Leq) were measured during drilling episodes. Frequency analysis in one third octaves covering the frequency bands 6.3 Hz to 20 k Hz was performed using a sound analyzing program.

RESULTS

When averaged over the entire procedure, the sound pressure level was highest for the surgeon and the assistant with values of 76.0 dBA and 72.5 dBA, respectively, during CI. Lpeak was 135.9 dBC. Leq for the stationary sound measurement was 74.2 dBA. During cortical bone work using a cutting burr, 84.6 dBA was measured. Mean values of L95% (estimation of the background noise) were between 55.8 dBA and 61.2 dBA. Frequency analysis showed the highest sound pressure level for all procedures was between 2.5 kHz and 3.15 kHz.

CONCLUSION

This is the first study to use personal sound dosimetry to monitor noise exposure during otosurgical drilling. In accordance with other studies, the results presented show sound levels below international occupational noise level regulations. However, the measured noise exposure during drilling could have negative effects on care providers based on unfavorable acoustical comfort.

Fifteen years of early hearing screening in Flanders: impact on language and education

OBJECTIVES

To assess the impact of fifteen years of universal neonatal hearing screening in Flanders on language development and the educational setting.

METHODOLOGY

An analysis of the database of Kind en Gezin from 1997 to 2012 and a long-term evaluation of the children referred to our centre after failed neonatal hearing screening. The CELF and PPVT language tests were performed.

RESULTS

Between 1997 and August 2012, bilateral hearing loss was confirmed in 2393 children in Flanders, of whom 11.4% were referred to our tertiary centre. The educational setting and language development of 84 children older than 5 years was evaluated and 54% of them had additional disabilities. Of the children without additional disabilities, 84% attended mainstream schools; 42% of children with additional disabilities entered mainstream education with additional support. There was a significant correlation between the number of additional disabilities and the education level (p < 0.001) and between the degree of hearing loss and educational placement (p < 0.001). Data on language development were available for 76% of the children and a significant correlation could be demonstrated only between the results of the PPVT language and the number of additional handicaps (p < 0.008).

CONCLUSIONS

The majority of children receiving early treatment after neonatal hearing screening enter mainstream education. The number of additional disabilities has a significant effect on education level and language development.

Long-term audiological follow-up of children with congenital cytomegalovirus

OBJECTIVE

To evaluate the audiological outcome of children with congenital cytomegalovirus infection.

METHODOLOGY

In a prospective study, the hearing of 98 congenitally cytomegalovirus-infected children born between January 2003 and July 2009 was systematically evaluated until the age of six using the Flemish CMV protocol. Symptomatic children with hearing loss at birth were treated with ganciclovir, if parents consented.

RESULTS

Seventy children passed initial screening, 28 had unilateral or bilateral hearing loss. In the normal hearing group, one asymptomatic and two symptomatic children developed late-onset hearing loss. Eight children in the group with hearing loss at birth received ganciclovir. Nine symptomatic and 11 asymptomatic children did not receive ganciclovir. In the treated group, 37.5% of the children had stable hearing loss, and 37.5% had progressive and/or fluctuating hearing loss. First progression or fluctuation always occurred after the age of one year. The hearing threshold improved in 25.0%. The improvement took place during or shortly after treatment. Hearing loss remained stable in 33.3% of the untreated symptomatic children, while progression or fluctuation occurred in 55.5%. In the asymptomatic group, hearing loss was most commonly stable (63.6%). The first change in the hearing threshold was almost always detected before the age of one year in both untreated groups.

CONCLUSIONS

Hearing loss caused by congenital cytomegalovirus infection cannot be defined unequivocally either with respect to the level of hearing loss or its evolution over time. Treating symptomatic children with ganciclovir leads to a better prognosis during the first year of life, after which progression or fluctuation again becomes more likely. However, overall, progression is more common in the untreated symptomatic group. Asymptomatic children with SNHL are more likely to have a stable hearing status.

Syndromic disorders in congenital hearing loss

OBJECTIVES

To investigate the aetiology of congenital hearing loss detected by the universal neonatal hearing screening programme (Algo) that was introduced in Flanders 15 years ago, and, more specifically, to investigate genetic causes.

METHODOLOGY

Diagnostic work-up of all children with confirmed hearing loss after referral by the Algo screening programme and screening at the neonatal intensive care unit (NICU) of our university hospital.

RESULTS

A hearing loss was confirmed in 505 of the 569 neonates (18% from NICU) referred between 1997 and 2011. After further examination, a genetic origin was identified in 84 (17%) of 100 children with a syndromic hearing loss. The most frequent syndromes are discussed.

CONCLUSION

A higher percentage of syndromic hearing loss was found than in the literature. This could be explained by the good cooperation with the human genetics department and the proportion of children retrieved from the neonatal intensive care unit.

Speech performance and sound localization abilities in Neurelec Digisonic® SP binaural cochlear implant users

In this prospective study the outcome of the Digisonic® SP Binaural cochlear implant (CI), a device enabling electric stimulation of both cochleae by a single receiver, was evaluated in 14 postlingually deafened adults after 12 months of use. Speech perception was tested using French disyllabic words in quiet and in speech-shaped noise at +10 dB signal-to-noise ratio. Horizontal sound localization in quiet was tested using pink noise coming from 5 loudspeakers, from -90 to +90° along the azimuth. Speech scores in quiet were 76% (±19.5 SD) in the bilateral condition, 62% (±24 SD) for the better ear alone and 43.5% (±27 SD) for the poorer ear alone. Speech scores in noise were 60% (±27.5 SD), 46% (±28 SD) and 28% (±25 SD), respectively, in the same conditions. Statistical analysis showed a significant advantage of the bilateral use in quiet and in noise (p < 0.05 compared to the better ear). Significant spatial perception benefits such as summation effect (p < 0.05), head shadow effect (p < 0.0001) and squelch effect (p < 0.0005) were noted. Sound localization accuracy improved significantly when using the device in the bilateral condition with an average root mean square of 35°. Compared with published outcomes of usual bilateral cochlear implantation, this device could be a valuable alternative to two CIs. Prospective controlled trials, comparing the Digisonic SP Binaural CI with a standard bilateral cochlear implantation are mandatory to evaluate their respective advantages and cost-effectiveness.

Levothyroxine replacement therapy after thyroid surgery

INTRODUCTION AND AIM

New entities, such as 'subclinical' over- and undersubstitution, are easily diagnosed after thyroid surgery due to improved testing methods, and the incidence of thyroidectomy with lifelong hormone substitution is increasing. Thus, there is a need to review conventional replacement therapy after thyroid surgery. We investigated the adequacy of our thyroid hormone replacement therapy for three months after total-, subtotal-, and hemithyroidectomy using an upper reference limit of thyrotropin (TSH) of 4.6 mU/L.

MATERIALS AND METHODS

Eighty-seven patients undergoing thyroidectomy for benign thyroid pathology participated. Levothyroxine (L-T4) treatment began five days after surgery. Preoperatively euthyroid patients received 150 microg L-T4 daily following total thyroidectomy, 100 microg L-T4 after subtotal thyroidectomy, and 50 microg L-T4 after hemithyroidectomy. Preoperatively hyperthyroid patients received 100 microg L-T4 following total thyroidectomy and 50 microg L-T4 following subtotal thyroidectomy. An average of six weeks after surgery, thyrotropin (TSH) was measured (reference limits 0.15-4.60 mU/L), and necessary dose adjustments were made.

RESULTS

Of the patients who were preoperatively euthyroid, 45% with total thyroidectomy, 42% with subtotal thyroidectomy, and 17% with hemithyroidectomy required L-T4 dose adjustments. Of the patients who were preoperatively hyperthyroid, 60% of those with total thyroidectomy and all of those with subtotal thyroidectomy required L-T4 dose adjustments.

CONCLUSIONS

To avoid over- and undersubstitution after thyroidectomy, an optimal replacement therapy dose is necessary. A small majority of our preoperatively euthyroid patients received adequate therapy. Endocrinological follow-up six weeks after surgery revealed the need for L-T4 dose adjustments, especially in preoperatively hyperthyroid patients. When the extent of resection was similar for hyperthyroid and euthyroid patients, the same initial dose of L-T4 was justified.