Biomedical subjects

A Aschendorff

Publications and source records attributed to A Aschendorff.

At least 19 recordsLinked to original sources

PubMed2006

[Evidence of a novel gene for the LAV-syndrome].

BACKGROUND: Both LAV- (large or enlarged vestibular aqueduct) and Pendred-syndrome are autosomal recessive diseases. In contrast to Pendred-syndrome, LAV-syndrome is characterised only by an enlarged vestibular aqueduct. Pendred-syndrome is a more complex disease. Classically it is characterised by sensorineural hearing loss and enlargement of the thyroid gland. Up to now, only mutations in SLC26A4 gene are known as being responsible for both syndromes. The gene for Pendred-syndrome (SLC26A4) has been localised by linkage analysis of chromosome 7q31. This protein is expressed in the inner ear, thyroid gland, kidney, and placenta. Functional analysis of the gene product (pendrin) in Xenopus laevis oocytes revealed that pendrin acts as an iodide/chloride and chloride/formate exchanger. METHOD: Each of the exons and flanking splice regions of the SLC26A4 gene were analysed by direct sequencing. Haplotype analysis was undertaken with microsatellite markers spanning a 5 Mbp area around the localisation of the SLC26A4 gene. RESULTS: In sequence analysis of 42 patients with bilateral enlargement of the vestibular aqueduct, no mutation could be identified in 30 % of cases. In some of these cases, a linkage to the gene localisation on chromosome 7q31 could not be detected. CONCLUSION: Our results indicate evidence for a second gene involved in the development of LAV-syndrome.

Adolescent↗

PubMed2006

Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study.

Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT's irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen's reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.

Ear, Middle↗

PubMed2006

[Single and temporally displaced second nerve lesions in an animal model and their clinical significance].

BACKGROUND: Surgical optic decompression after trauma has been discussed controversially. The surgical trauma is supposed to produce an additional nerve lesion with the danger of complete loss of vision. Alternatively, conservative high dose cortisone therapy has been recommended. METHODS: The functional and morphological consequences of a lesion after calibrated optic compression in one or two sessions were examined in an animal model using 29 Wistar rats. RESULTS: Depending on the duration and intensity of the lesion, we observed a linear decline in the number of neurons in the RGC (retinal ganglion cell) layer as well as an increasing reactivity to GFAP (glial fibrillary acidic protein) as an indication of central gliosis of astrocytes; however, this was independent on whether optic compression was performed in one or two sessions. CONCLUSIONS: To reduce secondary damage to the visual nerve and the central visual system that might increase with a persisting lesion, the indication for surgical relief of an eye affected by afference should be considered liberally, especially in view of the low morbidity of rhinosurgical intervention.

Animals↗

PubMed2006

[Ethisorb/Ethisorb durapatch for the transnasal duraplasty procedure?].

BACKGROUND: Defects of the dura in the rhinobasal area can be closed transnasally. Various procedures with autologous or alloplastic material can be chosen. METHOD: From 2001 to 2004, we closed a rhinobasal dura defect with Ethisorb or Ethisorb durapatch in sandwich technique in 8 patients. After smoothing the bone edges, Ethisorb is applied under microscopic or endoscopic view endocranially, extradurally as "underlay" to seal and absorb the liquor pressure pillar. Additionally, another Ethisorb implant as "underlay" is applied extracranially from endonasally as "underlay", and sealed with a further layer of nasal concha mucosa with fibrin glue. RESULTS: All patients were successfully treated with this technique. There were no evidences for persisting rhinoliquorrhoe after the period of wound healing. For hemostasia, a nasal package was applied for compression at the donor site of the inferior nasal concha. The former dura defect was at all times freely accessible in order to be able to recognize a possible new rhinoliquorrhoea early and to prevent a possible congestive secretion with superinfection. DISCUSSION: The material of Ethisorb and Ethisorb durapatch is stiff and can be easily modelled, so it is an alternative as an alloplastic material for endonasal closure of defined substantial defects of the dura with rhinoliquorrhoe.

Adult↗

PubMed2005

[Methods for evaluation of perimodiolar ci electrode arrays in human temporal bones].

BACKGROUND: Cochlear implants (CI) are the established treatment for cochlear deafness. Recently, indications for cochlear implantation have been expanded to include severely hearing-impaired patients. The use of bilateral implants seems to provide additional benefit. Moreover, new electrode designs, i. e. perimodiolar electrode arrays, aim at improving benefit for patients. However, in addition to providing functional improvements, modern electrode array development must also address safety aspects, because damage to the cochlear morphology (especially the osseous spiral lamina) may lead to degeneration of residual neuronal structures and bony obliteration or scarring within the cochlear ducts. METHODS: Therefore, insertion trauma of the newly developed electrode arrays in human temporal bones must be evaluated before applied to patients. Several methods for testing electrode location and intracochlear trauma are described. RESULTS: Combining cross-sectional imaging, histological analysis and elements of risk-assessment valid information about trauma and possible consequences for use in patients can be determined, based on our experience in 57 temporal bones. CONCLUSIONS: Following our results, safety studies with prototype electrode arrays should, in addition to radiological examination, always include careful histomorphological evaluation.

Adult↗

PubMed2005

[The influence of insertion depth on the preservation of residual hearing after cochlear implantation].

BACKGROUND: Cochlear implantation may be indicated in patients with bilateral severe sensory hearing loss. Patients with minimal residual hearing have more benefit from cochlear implantation than from optimal fitted hearing aids. However, it has to be considered that inner ear structures might be damaged during electrode insertion. METHODS: We analysed the influence of insertion depth on the preservation of residual hearing in 47 cochlear implant patients (type of implant: Nucleus 22 M or 24 M) by using the pure tone audiometry. Frequency-specific analyses of pre- and postoperative audiograms on the implanted side were performed, evaluating only frequencies above 500 Hz. The insertion depth was documented by stiffening rings outside the cochlea. RESULTS: Residual hearing was more obtained in cases with complete insertion of the electrode array than in those cases with incomplete insertion. In the frequencies 1000 and 4000 Hz these results are significant. CONCLUSION: In our opinion, the perceived resistance producing intracochlear damages and preventing the complete electrode-insertion at the same time is an explanation for the significantly poorer results of the patients with incomplete insertion.

Audiometry, Pure-Tone↗

PubMed2005

[The freiburg incision for cochlear implantation -- initial results].

BACKGROUND: Cochlear implant surgery is a well standardized therapy for rehabilitation of congenital or acquired deafness at all ages. Mastoidectomy, posterior tympanotomy, cochleostomy and electrode insertion are performed consistently worldwide. Recently newly developed types of incision are taken into account. In our experience over more than 15 years the extended endaural incision has proven to be reliable with a low complication rate. OBJECTIVE: To evaluate a modified retroauricular incision for clinical use and complication rate in cochlear implant surgery with devices of different manufacturers. MATERIAL AND METHODS: We performed a prospective analysis of cochlear implant surgeries between 03/2003 and 03/2004. In all cases a modified retroauricular incision was used. Necessary adaptations of incision, depending on the device used, and postoperative complications were evaluated. RESULTS: In 76 ears a retroauricular incision was performed. Depending on the shape and size of receiver/stimulator an extension of the incision was necessary. The mean observation time was 6.3 months. Intra- or postoperative complications were not observed. In one case a skin dehiscence following trauma 28 days after surgery was reported without dehiscence of fascia or implant failure with uneventful healing after secondary suture. CONCLUSIONS: With regard to the results with the extended endaural incision the modified retroauricular incision allows a safe access for cochlear implant surgery. Observation of long term results and outcomes in revision surgery is mandatory.

Adolescent↗

PubMed2005

[Endoscopic assisted endoluminal stapler-diverticulotomy of Zenker diverticulum].

INTRODUCTION: One of the advantages of endoluminal diverticolotomy in Zenker's diverticulum with the staple is the possibility of early rehabilitation. As the stapler allows to close the cut wound margins of the diverticulum threshold simultaneously with a clip suture, the patient can start oral food intake as early as 24 hours after surgery. The overview for the surgeon for correct placement of the clip device is limited due to the physiological narrowness of the pharyngeal tube. PATIENTS AND METHODS: We reduced the danger of malplacement by placing a temporary stomach tube as well as endoscopic control of the position of the stapler at the diverticulum threshold. RESULTS: 61 patients with Zenker's diverticulum stage Brombart I - IV have been successfully treated with this surgery technique since 1998. In two other patients a transcervical diverticulotomy was done because the diverticulum threshold could not be exposed clearly with the spread laryngoscope. In 10 patients a clinically symptomatical recurrent diverticulum (Brombart stage II) could be safely removed by a repeated endoscopically assisted stapler diverticulotomy. CONCLUSION: The advanced endoscopically assisted endoluminal stapler diverticulotomy in Zenker's diverticulum is convenient for the patient allowing prompt food intake and showing low morbidity and no mortality.

Adult↗

PubMed2005

[Guided surgery in a subtemporal approach in CPA tumors?].

BACKGROUND: Computer assisted surgery (CAS) permits the visualization of hidden bony covered structures invisible for the human eye with radiological 3d data sets. The surgeon might be able to orientate anatomically during surgery without having to prepare the according landmarks. This would mean less surgical traumatization and a shorter and smaller operation corridor. METHOD: We determined the use of CAS in a quality assurance analysis with the subtemporal approach in 8 patients with supra-meatal tumors type A of the cerebellopontine angle. Various navigation systems and methods for referencing for the registration of the patients' heads were used. The question was whether it is possible intraoperatively without preparation of known anatomical landmarks to define the borders of an optimal positioned temporary bone cap and to identify the bony covered inner auditory canal and its neuronal structures without orienting neurostimulation. RESULT: It was possible with CAS to assess intraoperatively the borders of a temporary bone cap above the cranially positioned mastoid cell. However, the objective inaccuracy of 2 to 28 mm observed during surgery did not allow a secure identification of the inner auditory canal. CONCLUSIONS: CAS with the subtemporal approach cannot replace the conventional preparation of known anatomical landmarks nor neurostimulation to identify neural structures, due to the expected high inaccuracy with the non-invasive referencing systems that are available today.

Adult↗

PubMed2005

Influence of ionizing radiation on nucleus 24 cochlear implants.

HYPOTHESIS: To evaluate the influence of conventional or hyperfractionated radiotherapy on Nucleus CI24M or CI24R(CS) implant systems. BACKGROUND: As a consequence of more than 70,000 cochlear implant recipients worldwide, the potential need for radiotherapy is an issue requiring consideration by both implantees and implantation centers. Conditions requiring radiotherapy of the head may include head, neck, or brain tumors. METHODS: The study examines the effect of ionizing radiation on cochlear implant function. The implanted devices examined were the Nucleus CI24M and Nucleus CI24R(CS). In a modeled study, two implants of each type were treated with fraction schemes most frequently used in clinical routine (e.g., conventional fractionation [total dose, 120 Gy] and hyperfractionation [total dose, 116 Gy]). Parameters quantified were the implant output amplitude changes at high and low current level (current levels 255 and 100, respectively), the charge balance of the biphasic pulse, and the accuracy of the impedance telemetry function. RESULTS: Within the clinically relevant dose range (< 80 Gy), implant function in all four devices was normal. Failure occurred in one Nucleus CI24R(CS) device treated with hyperfractionation. A dramatic drop in the output amplitude at 106 Gy was observed, and the impedance measurement failed at a total dose of 111 Gy. CONCLUSION: The results suggest that conventional or hyperfractionated radiotherapy can be applied safely at Nucleus CI24M or CI24R(CS) implant systems in a patient-like setting. Therefore, the authors propose that the results of the study can be applicable in clinical practice.

Cochlear Implants↗

PubMed2004

[Current developments in cochlear implantation].

Over the last 20 years, cochlear implantation has become a well accepted treatment in patients suffering from hearing loss or congenital deafness. Results have been impressive,and indications for a cochlear implant have been extended continuously. Thanks to a sophisticated diagnostic procedure, optimization of the surgical technique, and the progression of interdisciplinary cooperation in the field of rehabilitation, the acceptance of cochlear implantation is growing significantly. The manufacturers of the devices are making great efforts to miniaturize the external components of the system, and new developments in electrode arrays, combined with new speech coding strategies, result in better speech understanding. The new developments in electrode design, however, are not necessarily improvements over recent years. Nevertheless, a very well functioning network of physicians, scientists, and manufacturers has acted and reacted in an outstanding manner to identify possible causes of post-implantation meningitis, have taken immediate counter measures and presented possibilities of prevention.

Cochlear Implantation↗

PubMed2004

[Navigation-controlled cochleostomy. Is an improvement in the quality of results for cochlear implant surgery possible?].

BACKGROUND: The correct positioning of the electrode, which is the limiting factor for the functional integrity of cochlear implants, is decisively influenced by the cochleostomy. Localisation and form of the drilling canal have been solely defined by the surgeon during the operation and an enlargement of the drilling canal is often necessary. Thanks to the improved resolution of new slice imaging techniques, computed tomography allows an exactly defined optimal point for cochleostomy. MATERIAL AND METHODS: In a cadaver study, we examined whether the target defined with computed tomography can be reached in a reproducible way with the help of navigated computer assisted surgery. We chose titanium screw markers as the gold standard for referencing. RESULTS: There was a real deviation of 1.6 mm in the target field. Thus, in a cochleostomy with a diameter of 0.5 mm the goal was not reached in a reproducible way. With this deviation a target of 2.56 mm(2) is defined. CONCLUSIONS: A target assessed by navigation is better than one reached without navigation in view of reproducibility and accuracy. With further technical progress navigated cochleostomy will be possible.

Cadaver↗

PubMed2004

[Does computer-aided navigation of endonasal sinus surgery improve process quality and outcome quality?].

BACKGROUND: Ever since navigation technology was introduced into endonasal surgery, its impact on process and result of surgery has been debated. In this respect, factors of investment costs and additional costs for time exposure will be discussed as well. PATIENTS AND METHODS: In a retrospective analysis of quality assurance, the results of endonasal surgery by surgeons of different experience in 56 patients were evaluated. Preparation time, preoperative setup time as well as time of actual surgery were analysed and compared with possible indications for navigation. RESULTS: From our analysis a classification resulted dividing the indications for navigation into the following four different categories: redundant, reasonable, helpful, necessary. Navigation was redundant when it was dispensable and did not result in a clear improvement of process or outcome quality. Navigation has been proved reasonable when it helped to obtain additional information for improving process quality. It was considered helpful when the information obtained by navigation had an influence at least on the course and/or result of surgery. Navigation was necessary from the surgeon's point of view when the intervention in regard to the benefit-risk-ratio could not be justified without navigation, or only intraoperative slice imaging would allow surgery. CONCLUSION: Not only redundant, but also facultative and obligatory indications for navigation in endonasal surgery result from careful consideration of the risk-benefit-cost ratio. In standardized endonasal sinus surgery, like infundibulotomy or ethmoidectomy, however, navigation can be a hindrance to process quality and does not result in any advantage for outcome quality.

Adult↗

PubMed2004

[Results with the Contour cochlear implant in patients with cochlear otosclerosis].

BACKGROUND: Results after cochlear implant surgery may be complicated by postoperative facial nerve stimulation. Aim of the study presented was to evaluate postoperative results in implanting the straight Nucleus electrode array and the preformed Contour array in patients with deafness due to cochlear otosclerosis. METHODS: A retrospective analysis of intra- and postoperative reports of all patients with cochlear otosclerosis was carried out. Results with the Nucleus straight electrode array and the Contour array were compared with regard to postoperative facial nerve stimulation. RESULTS AND CONCLUSION: None of the Contour patients (n = 7) presented with postoperative facial nerve stimulation. This is in contrast to the majority (4 of 6) of patients being implanted with the straight electrode array. Our results indicate that the use of the Contour array is advantageous in patients being at risk for facial nerve stimulation. In addition intraoperative reports suggest a more reliable insertion of the Contour electrode array in cochlear otosclerosis with partial obliteration.

Cochlear Implants↗

PubMed2004

[Caloric stimulation of the vestibular organ after cochlear implant surgery].

BACKGROUND: Alterations of the vestibular organ after intracochlear insertion of the electrode array in cochlear implant (CI) surgery are estimated in the literature to be more than 30 % . By performing a most atraumatic electrode insertion following the "soft surgery technique" as described by Lehnhardt , the risk of postoperative vestibular dysfunction should be minimised. METHODS: In the present study we compared pre- and postoperative results of the caloric stimulation test in cochlear implant patients and analysed the influence of untimely opening of the perilymphatic space under cochleostomy. In addition we used a non-validated questionnaire, asking for continuous postoperative vertigo after cochlear implant surgery. RESULTS: From patients with preoperative normal or hyperfunction on the implanted ear (n = 32) approximately 16 % showed a hypofunction or nonfunction on the implanted side postoperatively, independent of the technique of the cochleostomy. Only 12 % (n = 98) of the patients who were without vestibular problems preoperatively described postoperative vertigo longer than two days in the questionnaires. CONCLUSIONS: Although we found no significant difference regarding the influence of the technique of the cochleostomy on the preservation of vestibular function, we conclude that the concept of an atraumatic electrode insertion reduces the risk of vestibular dysfunction after CI-surgery.

Adolescent↗

PubMed2004

[Identification of two heterozygous mutations in the SLC26A4/PDS gene in a family with Pendred-syndrome].

BACKGROUND: Pendred-syndrome is an autosomal recessive disease that is classically characterised by sensorineural hearing loss and enlargement of the thyroid gland. The gene SLC26A4/PDS for the pendred-syndrome has been localised by linkage analysis on chromosome 7q31. This protein is expressed in the inner ear, thyroid gland, kidney and placenta. Functional analysis in Xenopus laevis oocytes revealed that it acts as an iodide/chloride and chloride/formate exchanger. METHOD: Each of the exons and flanking splice regions of the SLC26A4/PDS gene was analysed by direct sequencing. RESULTS: In the involved family two heterozygous mutations could be detected which results by combination in hearing loss and deafness. CONCLUSION: By evidences of familial background in hearing loss and thyroid disorder it is reasonable to analyse the PDS gene for mutation to have early the possibility for medical care of linguistic development through hearing aid or CI-implantation.

Child↗

PubMed2004

[Obliterated cochlea in Cogan's syndrome -- implications for cochlear implant surgery].

BACKGROUND: Acute, often bilateral deafness in Cogan's syndrome or other autoimmune diseases is caused by autoimmune mediated inflammatory attack on the membranous labyrinth. Auditory rehabilitation in case of bilateral deafness can be achieved by cochlear implant surgery. METHODS: A retrospective analysis of all patients suffering from Cogan's syndrome that had received a cochlear implant, was carried out. RESULTS: 6 of 295 adult patients (2.6 %) that had received a cochlear implant, had become deaf due to Cogan's syndrome. Partial obliteration or ossifikation was encountered in all cases and influenced surgical procedure. In one case a fibrous obliteration of the scala tympani was found 8 weeks after acute onset of complete deafness. CONCLUSIONS: The course of obliteration is unknown. With regard to our results a fibrous obliteration may occur as early as 8 weeks after complete deafness. This has to be considered in counseling of patients. Only early cochlear implant surgery facilitates best possible rehabilitation results.

Adult↗

PubMed2004

[Electrophysiologic examinations in low frequency hearing impairment: clinical and prognostic aspects].

INTRODUCTION: Low-frequency hearing impairment (LFHI) is mainly associated to endolymphatic hydrops and shows a high variety of possible outcomes. Electrophysiologic examinations are widely recommended in diagnostics of LFHI, wheras up to now no data exist about the prognostic value of these examinations in a conservative therapeutic regimen. METHODS: In a quality assessment, we retrospectively evaluated the records of 90 patients, and performed an audiometric follow-up for analysis of long-time hearing data. All patients had undergone diagnostic electrocochleographic examination (ECochG) and then had been treated with rheologic infusions, followed by dehydrating infusions in patients lacking complete remission. The results of both therapeutic strategies and of long-time results were correlated to electrophysiologic findings. RESULTS: The prognosis of LFHI is significantly reflected by pretherapeutic electrocochleographic data. All significant parameters were associated to compound action potential (CAP) whereas parameters associated to cochlear microphonics (CM) did not include any utilizable prognostic value. In patients with a good outcome, the latency of CAP complex was significantly shorter, and the width of CAP complex significantly smaller than in patients with poor hearing outcome after rheologic and after dehydrating therapy and in long time assessment. The relation of summating potential (SP) und CAP was significantly smaller when the outcome was sufficient or good for either therapy and in long time analysis. Steep CAP-input-output-curves were associated to insufficient outcome after rheologic therapy and in long time assessment, but not for dehydrating therapy. CONCLUSIONS: The results indicate that ECochG is of significant prognostic value concerning hearing outcome after conservative therapy in patients suffering from LFHI. It can help the physician to counsel the patient and perform an effective management of the disease. We conclude that ECochG should be performed before the onset of therapy, including collection of SP and CAP data whereas CM parameters may be omitted.

Action Potentials↗