Search PubMed⌕ Search

Biomedical subjects

A Aschendorff

Publications and source records attributed to A Aschendorff.

33 records · Page 2Linked to original sources
PubMed2004

[Evaluation of the insertion-trauma of the Nucleus Contour Advance electrode-array in a human temporal bone model].

BACKGROUND: The development of intracochlear electrode arrays is aiming at a placement close to the modiolus with an insertion as atraumatic as possible. A new perimodiolar electrode model the Nucleus Contour Advance was to be evaluated regarding the possible intracochlear trauma. METHODS: The implantation of the Contour Advance electrode was performed in 11 frozen native temporal bones. Beneath a regular insertion in 5 temporal bones in 6 cases the insertion was carried out using the "advance-off-stylett" technique with a fixed stylett. The temporal bones were embedded in metacrylate based resin for histomorphological evaluation. The evaluation was performed regarding to the intracochlear placement close to the modiolus and the damage to intracochlear fine structures (basilar membrane, osseus spiral lamina). RESULTS: In 2 out of 11 cases we found a perforation from the scala tympani to the scala vestibuli independent of the insertion-technique. A severe intracochlear trauma was observed in one case with fracture of osseus spiral lamina using the AOS-technique. A close position to the modiolus could be achieved by insertion the scala tympani without perforation of the basilar membrane. CONCLUSIONS: The Nucleus Contour Advance electrode array showed minimal trauma in human temporal bones by using a standard insertion technique. By using the freehand AOS-technique a severe cochlear trauma is possible. Therefore further development in electrode design and the use of an insertion-tool is recommended.

Basilar Membrane↗
PubMed2004

Imaging procedures in cochlear implant patients--evaluation of different radiological techniques.

The purpose of this study was to evaluate the feasibility and usability of different radiologic methods (single-slice computed tomography (CT), multi-slice CT and rotational tomography (RT)) for assessment of the position of cochlear implant electrodes. Cochlear implants in an isolated human temporal bone and in a complete formalin-fixed cadaver head were examined and the electrode position was determined. Subsequently, the labyrinth bone was isolated out of the cadaver head and histologically examined to compare the results of histology with imaging. Single-slice CT reliably identifies the electrode inside the human cochlea; however, due to the technically based large electrode artifact its position inside the cochlear spaces (e.g. electrode position in scala tympani or scala vestibuli) cannot be detected. Multi-slice CT of the cadaver head also showed artifacts that complicate the assessment of electrode position. Using RT the electrode artifact is small and therefore the electrode position within the cochlear spaces, scala tympani versus scala vestibuli, can be assessed. This technique was also applicable in a complete cadaver head, which is in contrast with former studies. In conclusion, CT allows the identification of electrode arrays inside the human cochlea. Multi-slice CT permits a much more precise depiction of the electrode inside the cochlea. RT alone has minimized electrode artifacts to a high extent and permits the assessment of the electrode position within the scala tympani or scala vestibuli. As RT was performed successfully in a complete cadaver head, further studies for evaluation of the intracochlear electrode position can now be performed in patients.

Angiography, Digital Subtraction↗
PubMed2001

The Nucleus Contour electrode array: a radiological and histological study.

OBJECTIVES: To evaluate the handling and insertion trauma of the recently developed Nucleus perimodiolar Contour electrode array (Cochlear Ltd., Pty, Lane Cove, New South Wales, Australia) in human temporal bones compared with the Nucleus standard straight electrode array. STUDY DESIGN: E-perimental control group. METHODS: Twenty-nine fresh-frozen bones were implanted with different electrode arrays by an experienced cochlear implant surgeon, and evaluated both radiologically and histologically. RESULTS: Intracochlear insertion of the standard Nucleus straight electrode array was found to be atraumatic, confirming previous findings in the literature. Insertion of the Nucleus Contour electrode array resulted in instances of localized basilar membrane penetration causing the electrode array to move from the scala tympani into the scala vestibuli. However, this trauma did not result in any observable damage to the osseous spiral lamina or the modiolus. Basilar membrane penetration was observed in six of eight cochlear bones when a standard cochleostomy size (approximately 0.8 mm) and site (anterior and superior to the round window) were used. However, when the surgical technique was modified to use a slightly larger cochleostomy ( approximately 1.8 mm) situated closer to the round window and employ a partial stylet withdrawal technique during electrode insertion, the frequency of penetrations was restricted to two of seven bones. This trauma rate is comparable to that observed with other cochlear implants designs. CONCLUSIONS: Following our results, the design of the Nucleus Contour electrode appears to fulfill the safety requirements for an intracochlear electrode array, provided that the surgical insertion technique is modified in the manner outlined.

Basilar Membrane↗
PubMed2001

Cochlear structures after implantation of a perimodiolar electrode array.

OBJECTIVE: A perimodiolar prototype electrode array has been evaluated on 12 human temporal bone specimens. To achieve modiolar proximity, a fine Teflon positioner is attached to the tip and base of a conventional Nucleus 22 electrode array. METHODS: Intracochlear electrode position was examined by macroscopic preparation and confirmed by a cochlear view x-ray after insertion into human temporal bones. The temporal bones were examined with light microscopy for intracochlear trauma after insertion, explantation, and re-implantation of the perimodiolar array. RESULTS: Macroscopic preparation and x-ray confirmed close proximity of the intracochlear electrodes to the modiolar wall. In some bones, electrode insertion and positioning was performed without significant damage to intracochlear structures, but explantation caused varying degrees of trauma depending on the explantation technique used. Re-implantation and repeat explantation appeared to destroy most of the intracochlear architecture. CONCLUSIONS: The perimodiolar electrode array prototype with Teflon positioner cannot be recommended for clinical use, especially in children in whom the possibility for re-implantation is high.

Child↗
PubMed2000

A new method for extracting wooden foreign bodies from the upper esophagus.

A foreign body impacted in the esophagus is an emergency case that requires immediate treatment. Often the foreign body can be removed easily using forceps or loops. Sometimes, however, safe grasping and extraction may become very difficult. A patient swallowed a chestnut which then stuck in the upper esophagus. The chestnut was removed with a gynecological instrument with a spiral tip used for myoma fixation. Thereafter this technique was applied to in vitro tests with various kinds of meat and wood. In the clinical case, the chestnut could be removed with the spiral tip of the instrument for myoma fixation, whereas in the in vitro tests it was impossible to grasp meat or cut it into pieces. The removal of foreign bodies, such as wood, with the spiral tip of the instrument for myoma fixation during rigid esophagoscopy is an alternative to extraction with forceps or loops. This method is ineffective for the removal of pieces of meat.

Esophagoscopy↗
PubMed1999

Cochlear implants and electrical brainstem stimulation in sensorineural hearing loss.

Cochlear implants and multichannel auditory brainstem implants enable patients with bilateral total or profound hearing loss to receive at least acoustic information. Both types of prosthesis are based on electrical stimulation of the auditory pathway. Different speech coding strategies and the number of electrodes used may influence the postoperative results. The preoperative evaluation of patients is of utmost importance. The cochlear implant is suitable for patients with hearing loss due to inner ear disorders, but who have functioning hearing nerve. Patients with a defect of the hearing nerve can be provided with an auditory brainstem implant.

Brain Stem↗
PubMed1998

Tinnitus in Cochlear Implant Users: The Freiburg Experience.

Cochlear implantation is a well-accepted method of aural rehabilitation in deaf or severely hearing-impaired adults and children. A majority of patients not only suffer from hearing impairment but from tinnitus. The high rate of preoperative tinnitus in adults (68.1%) stands in contrast to assumed lower rates in children. Unknown are such factors as how tinnitus develops in children, how they realize what tinnitus is, and whether the mechanism of development of tinnitus differs from that in adults, respectively. Electrical stimulation of the auditory pathway is followed by loss, or at least reduction, of tinnitus in most cases (75%). Also, the insertional trauma alone is able to stop tinnitus in some patients. Attention must be paid to the low risk of developing tinnitus postoperatively. No reports are available regarding tinnitus in children. Though younger children may not be able to report, some adolescent patients report preoperative or postoperative tinnitus (or both) that is reduced by electrical stimulation at the rates seen in adults. Further investigations are needed to define the mechanism of tinnitus development in children and to define optimal stimulation modes and rates for tinnitus reduction with best auditory performance.

Journal Article↗
PubMed1997

[Early and long-term results of rehabilitation of cochlear implant patients]].

BACKGROUND: Cochlear implantation is nowadays a reliable and well-accepted method of auditory rehabilitation in selected adults and children. METHODS: We present rehabilitation data on 21 adult patients provided with the Nucleus CI22 M cochlear implant using the SPEAK strategy. RESULTS: Results of first tune-up show an open set speech understanding in approximately 50% of patients. Long-term results also reveal further improvement in patients who had no open set speech understanding. Our data seem to indicate similar results in comparison to other groups using the CIS strategy. CONCLUSIONS: In adults, open set speech understanding can be achieved even at the first tune-up. Results of early rehabilitation seem to be influenced by duration and etiology of deafness, experience with hearing aids, and other factors.

Adult↗
PubMed1997

Large vestibular aqueduct syndrome and its implication for cochlear implant surgery.

The large vestibular aqueduct syndrome (LVAS) is commonly found when presurgical computed tomography is performed in advance of cochlear implantation. We present data on two patients with LVAS, in whom computed tomography (CT) and magnetic resonance imaging (MRI) was performed. Cochlear implantation when these malformations are present may be complicated by an intraoperative gusher, but it appears to be safe and produces a favorable outcome.

Child, Preschool↗
PubMed1996

[Lermoyez syndrome--electrocochleographic studies].

BACKGROUND: Lermoyez's syndrome is usually regarded as a rare variant of Menière's disease with hearing improvement and reduction of tinnitus during vertiginous attacks. Electrocochleographic studies of this syndrome are restricted to one published case up to now. METHODS: In our ENT department we clinically and electrocochleographically examined three patients suffering from Lermoyez's syndrome. These results were compared to those typically found in Menière patients. RESULTS: Two of the three patients did not show an elevated summating potential or increased ratio of summating potential and compound action potential (SP/CAP ratio). There was no hearing improvement following oral glycerol administration, and the SP/CAP ratio did not change during a Lermoyez attack. On the other hand, we observed normal cochlear microphonics in ears affected by Lermoyez's syndrome, indicating good hair cell function. In one ear, the threshold of cochlear microphonics was even better than the pure tone threshold. CONCLUSIONS: Our observations suggest that endolymphatic hydrops may not be always the underlying pathologic correlate of Lermoyez's syndrome. Thus Lermoyez's syndrome should not be simply regarded as a variant of Menière's disease.

Action Potentials↗
PubMed1990

Marker haplotype association with growth in German cystic fibrosis patients.

In 84 families with 101 children with cystic fibrosis (CF) and 103 unaffected siblings, the haplotype of CF chromosomes was determined with six restriction fragment length polymorphism (RFLP) markers that span the CF gene locus. Patient groups with different genotypes in the more distant flanking marker loci MET D, MET H, and D7S8 differed significantly from each other with respect to percentile height and weight, and percentage of weight for height. Patients homozygous 1-1 in met D (TaqI) and met H (TaqI) were thin and tall when homozygous 1-1 in J3.11 (MspI), and small when homozygous 2-2 in J3.11. Heterozygosity in 3.11 and met H and homozygosity 1-1 in met D segregated with the most severe growth retardation. In contrast, growth was normal in patients who were heterozygous in met D and/or had an uncommon KM.19/XV-2c haplotype. Most patients with pancreatic sufficiency and/or borderline sweat test values were carrying rare haplotypes on their CF chromosomes. Adult patients clustered in genotype groups with normal height percentile distributions. This association between haplotype and clinical severity of CF in the German population provides evidence for genetic microheterogeneity of the CF locus, either because of the existence of multiple alleles of the CF gene itself and/or because of the existence of closely linked polymorphic genes that control growth and development and hence modulate the clinical course and prognosis of CF.

Adolescent↗