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Biomedical subjects

B Schwab

Publications and source records attributed to B Schwab.

At least 19 recordsLinked to original sources
PubMed2006

[Titanium oxide ceramic as an implantation material in otosurgery: animal experimental results and surgical technique].

BACKGROUND: For the experimental animal study to evaluate a new ossicular chain replacement prosthesis, we developed a new technique for surgical implantation into the middle ear of rabbits. The selection of the species was based on its similarity to human middle ear anatomy and the favored, standardized, microsurgical approach to the middle ear cavity. METHOD: For the study we included a total of 34 approximately 6-month-old female white rabbits (New Zealand) with a weight of 3.2 to 4.4 kg. The implants used were constructed of ceramic materials TiO(2) (titania) with different pore size. Directly before the implantation of the TORPs, as well as at 28, 84 and 300 days after implantation, electric response audiometry was used to determine the hearing thresholds of the animals (bone conduction click stimulus nHL). The Erbium Yag-Laser was used to cut out the originally ossicular chain. RESULTS: After implantation we could not detect any stenosis of the outer ear canal or perforation of the tympanic membrane. The conductive hearing threshold was in the range of 4.21 +/- 6.68 dB nHL (n = 131). The hearing level showed no significant difference before and after surgery (p > 0.05). CONCLUSIONS: The laser surgery is a very safe procedure for prosthesis implantation in the middle ear of rabbits..

Animals↗
PubMed2006

Intraoperative computed tomography in otorhinolaryngology.

CONCLUSIONS: Intraoperative CT surgery provides the surgeon with additional information about the altered surgical site in difficult anatomical situations. The skull base and lamina papyracea may be revealed by means of intraoperative CT, which may be beneficial in endonasal sinus surgery involving difficult surgical sites, although individual ethmoid cells cannot be assessed owing to blood artefacts. This provides the surgeon with valuable information that may facilitate the procedure considerably. In soft-tissue surgery it is advisable to apply a contrast agent in order to achieve good soft-tissue contrast, thus allowing the tumour to be adequately distinguished from benign tissue. The intraoperative application of CT is a fairly time-consuming procedure, partly owing to the preparation time (set-up of the appliance; 10-min warming-up phase) and partly due to the length of time required to calculate each image (15 s). OBJECTIVE: CT is a well-established imaging method for the assessment of osseous and soft-tissue structures in the head and neck region. Saving information and transferring it to the intraoperative site may, however, be problematic. Computer-assisted navigation systems are now able to assist difficult surgical procedures in the field of otolaryngology. To investigate the indications for intraoperative CT, we used it in various surgical procedures in the head and neck region. MATERIAL AND METHODS: Intraoperative CT was applied using the Tomoscan M in 46 cases in order to demonstrate the surgical benefit of the following procedures: endonasal surgical procedures on the paranasal sinuses (maxillary and ethmoidal sinusitis, anterior fracture of the sphenoidal sinus); tumour removal by means of laser surgery (carcinomas of the hypopharynx and larynx); and cochlear implantation (to verify the electrode position). After positioning the patient on the CT table, the workstation was set up in the operating theatre. If necessary, the gantry could be moved over the patient's head without repositioning the patient. RESULTS: Intraoperative CT was used to assist in the exposure of the skull base and lamina papyracea in endonasal surgery of the paranasal sinuses. Individual ethmoidal sinuses could not be evaluated owing to blood artefacts. Intraoperative imaging proved particularly helpful in revision surgery for chronic sinusitis in cases with missing anatomical landmarks owing to previous surgeries, where there is an increased risk of inflicting damage to the skull base or orbita. The resection margins can be determined in craniofacial resections. In soft-tissue procedures, such as tumour removal by means of laser surgery, it proved possible to visualize the resection borders of malignant tumours. Assessment of the electrode position in cochlear implantation is particularly useful in revision cases and in cases of cochlear obliteration.

Cochlear Implantation↗
PubMed2006

Four years' experience with the minimally invasive surgical approach in cochlear implant surgery.

This is a prospective study on 808 profoundly or totally deaf patients who underwent either unilateral or bilateral cochlear implantation, involving a minimally invasive surgical approach, at the Medical University of Hannover's Department of Otolaryngology between May 2001 and May 2005. Advanced Bionics, Cochlear and MED-EL devices were used, the latter having been in use at our department since the beginning of 2003. The aim of our investigation was to determine the optimal surgical technique, evaluate safety aspects and gauge patient satisfaction with this minimally invasive surgical approach during cochlear implantation. Surgical technique is analysed. Complications such as skin flap problems did not occur. The use of this minimally invasive surgical technique did not increase the surgical risk. This procedure proved both cosmetically and psychologically beneficial for patients, especially for children and their parents.

Adult↗
PubMed2004

[Bone ablation using ultrashort laser pulses. A new technique for middle ear surgery].

OBJECTIVES: Laser applications within the tympanic cavity area are widely accepted. Commonly used systems are CO(2), argon, KTP and erbium devices. The disadvantages are heat development and/or acoustic load of the inner ear. A new laser with ultra short pulses was examined concerning its ablation characteristics and tested for possible applications in the tympanic cavity. METHODS: Investigations on human ossicles and porcine compacta were performed with a femtosecond laser in order to determine the ablation parameters. This included measurements of the dependency of the threshold energy on the pulse duration and the determination of the ablation ratio using different pulse energy levels. On the basis of histological slices the thermal damages of the bone were examined. Additionally, the processed samples were analyzed with an optical microscope and with a scanning electron microscope in order to evaluate the quality of the perforations. RESULTS: The measurements showed that the threshold energy has a lower level than the threshold energy of the conventional laser systems. At a pulse duration of 180 fs the smallest fluence, with which an erosion can be achieved, is below 1 J/cm(2). With increasing pulse duration the necessary threshold energy also rises. Due to the low energy level necessary for ablation and the extremely short pulse duration, less thermal damage is induced to the surrounding bone tissue as compared to conventional laser systems. The analysis of the scanning electron microscope demonstrates the extreme precision of this laser system. The achieved accuracy of the incisions and drillings ranges in the microm-area. CONCLUSIONS: The fs laser represents a new surgical tool for middle ear surgery. It works efficiently and in a touch-free procedure. Due to its high precision and the reduced side effects an advantage in the handling of bony structures is to be expected in relation to other laser systems. Apart from the perforation of the stapes footplate, in particular the handling and modelling of the incus, a further field of applications includes enhanced coupling, e. g. for implantable hearing aids and ossicular chain replacement prosthesis.

Animals↗
PubMed2004

[Use of the round window micro cath for inner ear therapy - results of a placebo-controlled, prospective study on chronic tinnitus].

BACKGROUND: The local therapy of inner ear diseases provides a means of directly applying pharmacological substances and delivering electrical stimulation to inner ear structures. Problems relating to dosage, systemic effects and the blood-cochlear barrier are thus avoided, which is not the case with systemic therapy. The preferred access point is the membrane of the round window. PATIENTS AND METHODS: An appropriately shaped catheter (DURECT Corporation, Cupertino, CA, USA), whose double-lumen passage system permits the variation of concentration and flow, is inserted into the round window niche. In a prospective, placebo-controlled clinical study, this application system was tested in 20 patients with chronic tinnitus. Following implantation the substances lidocaine, glutamate, glutamic acid and caroverine were applied via an attached external micropump. RESULTS: The values for tinnitus loudness, level of irritation caused by the tinnitus and subjective effectiveness of the therapy - measured by means of the visual analog scale (VAS) - showed no significant change, although the most marked improvement was indicated for caroverine. CONCLUSIONS: These results indicate that a positive effect was observable only in a proportion of the patients. Continuous therapy of tinnitus and inner ear diseases will only be possible once a totally implantable microdosage system has been developed.

Administration, Topical↗
PubMed2004

[3D-Visualisation of the middle ear by computer-assisted post-processing of helical multi-slice CT data].

Post-processing of CT-data allows non-invasive 3D-Visualisation of the middle ear for diagnosis and surgical planning. In this study different post-processing techniques and the clinical application of a 3D-postprocessing algorithm in a large number of patients are presented. 20 normal patients, 6 dissected temporal bones and 213 patients with suspected middle ear pathology were examined using a low-dosage Multi-Slice CT protocol. Virtual endoscopic views of the middle ear and 3D-images of the ossicles were generated using a standardised algorithm. Evaluation of the image quality was performed. The virtual views of the dissected temporal bones were compared to real views. In 32 patients high-quality 3D-models of the individual anatomical structures were generated and displayed using different visualisation techniques. The standardised and evaluated method enabled visualisation of the normal middle ear anatomy. Assessment of different pathologies, especially malformation, trauma, implants and postoperative alterations, was facilitated. The high-quality 3D-models allowed precise imaging of the anatomical structures. 3D-Visualisation of the middle ear using CT-data is beneficial for radiological diagnosis and surgical planning in cases of complex middle ear pathology as a complementary examination technique.

Adolescent↗
PubMed2004

[The value of dynamic posturography (Equitest) in preparing an expert's report].

BACKGROUND: Expert appraisals of vestibular disorders and their effects on daily life are essentially based on an evaluation of the patient's subjectively described symptoms. The aim of the present study was to ascertain the extent to which dynamic posturography is able to assist in the preparation of expert's reports. MATERIAL AND METHODS: 60 patients underwent a survey of their balance impairment. Both a nystagmus analysis, with its objective criteria, and dynamic posturography were carried out. The investigation into reduction of fitness for work (MdE) made reference to the criteria specified in the table by STOLL. The data obtained were subjected to both correlation and variance analysis. RESULTS: Although the results of this analysis revealed no direct statistical dependency, they indicated a tendency for the composite values to be correlated with the nystagmus scores and/or the MdE values (when the nystagmus score and/or the MdE increases, the composite value decreases). CONCLUSIONS: The Equitest is, according to the available data, not able to replace the currently valid MdE scores. Nevertheless, it represents a means of providing objective data about the vestibulo-spinal reflex. The test also reveals any tendencies towards simulation and aggravation. In the context of a specific nystagmus analysis, the Equitest offers an additional means of providing an objective background to back up the more subjective assessment of MdE.

Adolescent↗
PubMed2003

Regulation of cell expansion by the DISTORTED genes in Arabidopsis thaliana: actin controls the spatial organization of microtubules.

The control of the directionality of cell expansion was investigated using a class of eight genes, the so-called DISTORTED (DIS) genes, that are required for proper expansion of leaf trichomes in Arabidopsis thaliana. By tracing the separation of latex beads placed on the trichome surface, we demonstrate that trichomes grow by diffuse rather than tip growth, and that in dis mutants deviations from the normal orientation of growth can occur in all possible directions. We could not detect any differences in intracellular organization between wild-type and dis-group mutants by electron microscopy. The analysis of double mutants showed that although the expression of the dis phenotype is generally independent of branching and endoreduplication, dis mutations act synthetically in combination lesions in the ZWI gene, which encodes a kinesin motor protein. Using a MAP4:GFP marker line, we show that the organization of cortical microtubules is affected in dis-group mutants. The finding that most dis-group mutants have actin defects suggested to us that actin is involved in organizing the orientation of microtubules. By analyzing the microtubule organization in plants treated with drugs that bind to actin, we verified that actin is involved in the positioning of cortical microtubules and thereby in plant cell expansion.

Actins↗
PubMed2001

Prenatal diagnosis of congenital heart disease and neonatal outcome--a six years experience.

BACKGROUND: Prenatal diagnosis of congenital heart disease (CHD) is important for proper perinatal and neonatal management, as CHD occurs in approximately eight of 1000 live births. Antenatal detection of cardiac malformations is crucial as altered obstetric and neonatal management may be required and the neonate will benefit from delivery at a tertiary care center. METHODS: A retrospective comparison between pre- and postnatal diagnoses was accomplished. All fetal echocardiographic scans performed and CHD's detected postnatally between January 1994 and December 1999 by the department of obstetrics and gynecology and pediatric cardiology - Grosshadern, Munich University Hospital were reviewed. RESULTS: The incidence of CHD was 1.5% (116/ 7913). CHD was suspected by prenatal ultrasound in 57 fetuses. Postnatally, 116 congenital cardiac anomalies were diagnosed. Overall, the intrauterine detection rate was 38% (44/116). 72% (84) of the diagnosed anomalies were Septal Defects, 16% (19) disorders of the Atrioventricular Valves and 11% (13) Anomalies of the Great Vessels. In 10% (11) of fetuses chromosomal abnormalities were found. 8% (9) newborns suffered from congenital syndromes. In 55% (64) children were delivered preterm (<37 weeks of gestation). 5% (6) of the neonates required surgery within their first year of life. 28% (33) of children with CHD did not survive the first year of life. CONCLUSION: As the prenatal diagnosis is important for pre-, peri- and postnatal management, diagnostic accuracy is essential. Nevertheless, the accuracy of postnatal pediatric echo still exceeds that of the prenatal scan.

Adolescent↗
PubMed2001

Navigation with the StealthStationtrade mark in Skull Base Surgery: An Otolaryngological Perspective.

The introduction of computer-assisted navigation systems has played a significant role in assuring the integration and consistent intraoperative use of radiological information. We used a frameless stereotactic navigation system to treat 62 patients with a variety of skull base pathologies. The optoelectric appliance uses digital imaging information to locate surgical instruments in the operative area. The aim of this study was to evaluate the clinical accuracy, practicality, and impact of this navigation system on otolaryngological procedures. In conjunction with rigid head fixation and bone-anchored registration markers, the precision of registration was 0.8 mm and the accuracy of clinical measurements was less than 2 mm. With conventional fiducials and flexible head positioning, deviations were as large as 4.5 mm. The additional use of surface registration increased the precision of registration. Preoperative preparations took 15 to 35 minutes, depending on the complexity of the planning. Intraoperative computer support is an important aid to a surgeon's orientation, especially when a patient's anatomy is atypical. Navigation systems will likely improve the quality of surgery and facilitate training.

Journal Article↗
PubMed2001

Effects of cytochalasin D and latrunculin B on mechanical properties of cells.

Actin microfilaments transmit traction and contraction forces generated within a cell to the extracellular matrix during embryonic development, wound healing and cell motility, and to maintain tissue structure and tone. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and tissues. Cytochalasin D and Latrunculin are commonly used reagents that, by different mechanisms, alter the state of actin polymerization or the organization of actin filaments. We have investigated the effect of a wide range of Cytochalasin D and Latrunculin B concentrations (from 40 pM to 10 microM) on the mechanical properties of the cells within fibroblast populated collagen matrices. Contractile force and dynamic stiffness were measured by uniaxial stress-strain testing. The range of effective concentrations of Cytochalasin D (200 pM-2 microM) was broader than that of Latrunculin B (20 nM-200 nM). Activating the cells by serum did not change the effective range of Cytochalasin D concentrations but shifted that of Latrunculin B upward by tenfold. Simple mathematical binding models based on the presumed mechanisms of action of Cytochalasin D and Latrunculin B simulated the concentration-dependent mechanical changes reasonably well. This study shows a strong dependence of the mechanical properties of cells and tissues on the organization and degree of polymerization of actin filaments.

Actins↗