Assen Koitschev

Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS

This study aims at substituting the essential functions of photoreceptors in patients who are blind owing to untreatable forms of hereditary retinal degenerations. A microelectronic neuroprosthetic device, powered via transdermal inductive transmission, carrying 1500 independent microphotodiode-amplifier-electrode elements on a 9 mm2 chip, was subretinally implanted in nine blind patients. Light perception (8/9), light localization (7/9), motion detection (5/9, angular speed up to 35 deg s−1), grating acuity measurement (6/9, up to 3.3 cycles per degree) and visual acuity measurement with Landolt C-rings (2/9) up to Snellen visual acuity of 20/546 (corresponding to decimal 0.037 or corresponding to 1.43 logMAR (minimum angle of resolution)) were restored via the subretinal implant. Additionally, the identification, localization and discrimination of objects improved significantly (n = 8; p < 0.05 for each subtest) in repeated tests over a nine-month period. Three subjects were able to read letters spontaneously and one subject was able to read letters after training in an alternative-force choice test. Five subjects reported implant-mediated visual perceptions in daily life within a field of 15° of visual angle. Control tests were performed each time with the implants power source switched off. These data show that subretinal implants can restore visual functions that are useful for daily life.

Randomized, double blind, placebo controlled trial on the safety and efficacy of continuous intratympanic dexamethasone delivered via a round window catheter for severe to profound sudden idiopathic sensorineural hearing loss after failure of systemic therapy.

To study the safety and efficacy of continuous intratympanic dexamethasone‐phosphate (Dex‐P) for severe to profound sudden idiopathic sensorineural hearing (ISSHL) or sudden idiopathic anacusis after failure of systemic therapy.

Management of chronic rhinosinusitis in CF

Routine CF management often does not include upper airway (UAW) assessment although CFTR defects equally affect the sinonasal mucosa. Up to 50% of CF patients have chronic rhinosinusitis (CRS) and/or nasal polyps, and almost 100% reveal UAW abnormalities on CT scan. CRS impairs quality of life. UAW dysfunction in filtering, humidifying, and warming inspired air affects lower airways and the UAW is a potential site of first colonization and a reservoir for opportunistic bacteria. Therefore, UAW pathology substantially affects overall health in CF. Standard treatments are scarce and mostly lack evidence. Nasal douche can remove mucus and crusts. Recently, delivery of dornase alfa using a vibrating aerosol has shown potential as treatment for CF-related CRS. Surgery is indicated when conservative approaches fail but postoperative relapse is frequent. In summary, upper airway involvement in CF is undertreated and requires prospective investigation and an interdisciplinary consensus on diagnosis and therapy.

Outcomes research analysis of continuous intratympanic glucocorticoid delivery in patients with acute severe to profound hearing loss: Basis for planning randomized controlled trials

Conclusions. The data presented herein form the basis for conducting randomized placebo-controlled clinical trials evaluating the safety and efficacy of salvage treatment in patients with idiopathic sudden severe sensorineural hearing loss (but not anacusis) refractory to initial systemic therapy. Comparison of different application protocols and drug delivery systems will allow assessment of the value of continuous versus intermittent intratympanic glucocorticoid drug delivery. Objectives. To describe and critically evaluate the results of continuous intratympanic glucocorticoid delivery in patients with acute unilateral severe and profound sensorineural hearing loss refractory to initial systemic therapy and to compare the outcome with a historical control group. Material and methods. In a retrospective chart review, treatment results were analyzed in 23 patients with acute severe and profound hearing loss and failure of systemic standard therapy who received a continuous intratympanic delivery of glucocorticoids as a salvage treatment. Audiological results were compared within the local therapy group and with the results of an historical control group who did not receive salvage treatment. The study and control groups were matched with respect to hearing loss after initial systemic treatment failure. Results. The average pure-tone threshold after intratympanic salvage treatment showed a statistically significant improvement of 15 dB (95% CI 7–24 dB; p<0.001). After exclusion of patients with complete anacusis, i.e. a non-measurable hearing threshold, the local therapy group showed a significantly better improvement (mean 19 dB; 95% CI 6–32 dB) than the historical control group (mean 5 dB; 95% CI  − 2–11 dB; p<0.05).

Lateral Mechanical Coupling of Stereocilia in Cochlear Hair Bundles

For understanding the gating process of transduction channels in the inner ear it is essential to characterize and examine the functional properties of the ultrastructure of stereociliary bundles. There is strong evidence that transduction channels in hair cells are gated by directly pulling at the so-called tip links. In addition to these tip links a second class of filamentous structures was identified in the scanning and transmission electron microscope: the side-to-side links. These links laterally connect stereocilia of the same row of a hair bundle. This study concentrates on mechanical coupling of stereocilia of the tallest row connected by side-to-side links. Atomic Force microscopy (AFM) was used to investigate hair bundles of outer hair cells (OHCs) from postnatal rats (day 4). Although hair bundles of postnatal rats are still immature at day 4 and interconnecting cross-links do not show preferential direction yet, hair bundles of investigated OHCs already showed the characteristic V-shape of mature hair cells. In a first experiment, the stiffness of stereocilia was investigated scanning individual stereocilia with an AFM tip. The spring constant for the excitatory direction was 2.5 +/- 0.6 x 10(-3) N/m whereas a higher spring constant (3.1 +/- 1.5 x 10(-3) N/m) was observed in the inhibitory direction. In a second set of experiments, the force transmission between stereocilia of the tallest row was measured using AFM in combination with a thin glass fiber. This fiber locally displaced a stereocilium while the force laterally transmitted to the neighboring untouched taller stereocilia was measured by AFM. The results show a weak force interaction between tallest stereocilia of postnatal rats. The force exerted to an individual stereocilium declines to 36% at the nearest adjacent stereocilium of the same row not touched with the fiber. It is suggested that the amount of force transmitted from a taller stereocilium to an adjacent one of the same row depends on the orientation of links. Maximum force transmission is expected to appear along the axis of interconnecting side links. In our studies it is suggested that transmitted forces are small because connecting side links are oriented very close to an angle of 90 degrees with respect of the scan direction (excitatory-inhibitory direction).

Tracheal stenosis and obliteration above the tracheostoma after percutaneous dilational tracheostomy

Percutaneous dilational tracheotomy (PDT) as opposed to the conventional surgical tracheostomy is a procedure that allows airway control in critically ill patients without surgical exposure of the trachea. Based on the Seldinger technique, dilators are passed along a guiding wire through a small neck incision into the trachea under endoscopic surveillance. This separates the tracheal rings and results in a stoma. As opposed to the regular surgical tracheostoma, a PDT-stoma is not epithelialized. The procedure is cost effective and little time consuming. Considering the increasing number of performed PDTs in the last few years, we feel a need to be aware of possible long-term complications. Thus, in this report, we describe three cases of tracheal stenosis/obliteration after a PDT procedure. In all cases, tracheal narrowing occurred above the level of the stoma. This suggests a procedure-related mechanism, i.e., tracheal ring invagination and the consecutive development of granulation tissue, rather than a mechanism based on the duration of the cannulas placement, which would normally produce the stenosis below the stoma in the area of the cuff. Toward the end of the article, we provide evidence for this hypothesis and thus present a new subset of long-term complications after PDT.

Mechanical stimulation of individual stereocilia of living cochlear hair cells by atomic force microscopy.

This paper describes the investigation of elastical properties and imaging of living cochlear hair bundles of inner (IHC) and outer hair cells (OHC) on the level of individual stereocilia. A custom-made AFM-setup was used, allowing to scan the mechano-sensitive structures of the inner ear under direct control of an upright differential interference contrast (DIC) microscope with a water-immersion objective. Scanning electron microscopy (SEM) images of the identical hair bundles obtained after AFM investigation demonstrated that forces up to 1.5 nanonewton (nN) did not cause obvious damage of the surface morphology of the stereocilia. These are the first images of hair bundles of living sensory cells of the organ of Corti by AFM. They display the tips of individual stereocilia and the typical V-shape of ciliary bundles. Since line scans clearly show that slope and force interaction depend on the elastical properties of stereocilia, quantitative stiffness measurements and stimulation of single transduction channels are suggested.

Pathogenesis and Management of Nasal Polyposis in Cystic Fibrosis

Beginning in preschool age, during their lives, up to 50% of cystic fibrosis (CF) patients experience obstructing nasal polyposis (NP), which is rare in non-CF children. Pathogenetic factors of NP in general and especially in CF are still obscure. However, defective epithelial ion transport from mucosal glands plays a central role in CF, and viscous secretions impair mucociliary clearance, promoting chronic pathogen colonization and neutrophil-dominated chronic inflammation. Presently, CF-NP is not curable but can be clinically stabilized, though the large variety of proposed treatment modalities indicates a lack of standardization and of evidence of treatment efficacy. When conservative measures are exhausted, surgical intervention combining individually adapted endoscopic sinus surgery and supportive conservative treatment is performed. Topical steroids, approved as the gold standard for non-CF NP, may be beneficial, but they are discussed to be less effective in neutrophilic inflammation, and CF-specific antimicrobial and mucolytic therapy, as is true of all treatment modalities, urgently requires evaluation by controlled clinical trials within interdisciplinary networks.

Transtympanic Endoscopy for Drug Delivery to the Inner Ear Using a New Microendoscope

Anatomic variations of the round window (RW) niche found in approximately 33% of human temporal bones may account for some ofthe problems associated with local drug delivery to the inner car. A microendoscope with a total outer diameter of 1.2 mm was developed in particular for easy visualization and of drug delivery to the RW niche. It incorporated a thin fiber optic, a working/laser channel (0.3 mm) and an irrigation/suction channel (0.27 mm). When compared to a common 30 degree lens optic, with the microendoscope a greater area of the round window niche could be overseen. In addition, the endoscope could be advanced directly upon the surface of the RW membrane (RWM). The microendoscope may be used for evaluation of the anatomy of the RW niche prior to the placement of local drug delivery systems, for application of drugs directly onto the surface of the RWM or to verify the correct placement of inner ear drug delivery systems.

Hearing loss in Muckle-Wells syndrome.

OBJECTIVE Muckle-Wells syndrome (MWS) is an inherited autoinflammatory disease characterized by fevers, rashes, arthralgia, conjunctivitis, and sensorineural hearing loss. In MWS, NLRP3 gene mutations are associated with excessive interleukin-1 release. The aims of this study were to determine the otologic characteristics of MWS, define trajectories of hearing loss, and explore the association with distinct NLRP3 genotypes. METHODS A prospective observational cohort study of children and adults diagnosed as having MWS was conducted at a single center. NLRP3 gene mutations were determined. Patients underwent standardized clinical, laboratory, and otologic assessments, including pure tone audiometry, vestibular organ testing, and tinnitus evaluation. Trajectories of hearing loss were defined for each genotype. The genotype-specific risk of progression of hearing loss was determined. RESULTS A total of 33 patients ages 3-75 years who were members of 5 families with 4 different NLRP3 gene mutations were included. The majority of patients (67%) experienced bilateral sensorineural hearing loss. Even in cases of profound hearing loss vestibular reactivity remained normal. Fourteen adult patients reported nondebilitating tinnitus. Overall, hearing impairment progressed with age. Patients with the T348M mutation were at highest risk of rapid progression of sensorineural hearing loss. CONCLUSION Patients with MWS are at risk of developing progressive sensorineural hearing loss without vestibular involvement. Hearing impairment starts at high frequencies and can subsequently progress to profound hearing loss. Progression is age dependent. Patients with different NLRP3 mutations had distinctly different trajectories of hearing loss, suggesting a mutation-specific risk that should be considered when making treatment decisions.