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Biomedical subjects

K Schorn

Publications and source records attributed to K Schorn.

At least 19 recordsLinked to original sources
PubMed2000

Heparin-induced extracorporal low-density-lipoprotein precipitation (H.E.L.P.) to improve the recovery of hearing in patients with sudden idiopathic hearing loss.

The pathogenesis of sudden hearing loss (SHL) is still not well understood. Possible causes include increased blood viscosity, microthrombosis or altered blood flow. Hypercholesterolemia, hyperfibrinogenemia and increased platelet aggregation are frequently observed in patients with SHL. The aim of this study was to investigate whether drastic lowering of plasma cholesterol and fibrinogen by selective extracorporal apheresis could have a beneficial effect on hearing recovery in these patients. Seven patients with SHL were treated with an extracorporal procedure removing fibrinogen and cholesterol from plasma. Six of the seven patients showed an immediate improvement in auditory thresholds following a single treatment of heparin-induced low-density lipoprotein precipitation. These findings indicate for the first time that acute and drastic removal of plasma fibrinogen and low-density lipoproteins may be an effective clinical method for the treatment of patients with SHL.

Adult↗
PubMed2000

[Use of auditory field measurement in patients with otosclerosis].

BACKGROUND: Middle ear surgery sometimes leads to unpleasant auditory impressions such as distortion or hyperacusis that cannot be detected by conventional audiometric testing. METHOD: Sixty-one patients with conductive hearing loss caused by otosclerosis underwent audiological evaluation, which included a questionnaire followed by testing of the audiometric threshold, speech audiometry, and assessment and quantification of loudness perception with a commercial system (WESTRA). This investigation includes the postoperative measurement of hearing improvement and the patients' subjective impressions regarding hearing increase, distortion of speech, and hyperacusis. RESULTS: Hearing improved in 88% of the patients. A quantification of this hearing increase was possible with pure tone audiometry and the Freiburg speech discrimination test. Reduced hearing threshold and lack of improvement in speech discrimination was confirmed by conventional hearing measurements. However, the presence of hyperacusis and distortion of speech could be determined by conventional audiometry in only 50% of cases. It was interesting to note that the subjects who reported speech distortion and hyperacusis in the questionnaire were identified by their increased loudness perception using the categorical loudness scaling. CONCLUSION: Category loudness scaling appears to be a valuable additional clinical test to characterize postoperative phenomena as distortion of speech and hyperacusis in patients undergoing stapes surgery.

Adult↗
PubMed1999

Bacterial meningitis in adults: demonstration of inner ear involvement using high-resolution MRI.

OBJECTIVE: To visualize the sites involved in audiovestibular dysfunction during bacterial meningitis in adults and to relate these findings to the extent of hearing impairment and vestibular dysfunction. BACKGROUND: Hearing impairment is among the most frequent complications of bacterial meningitis. METHODS: High-resolution MRI (HR-MRI) of the inner ear was performed in seven adult patients with hearing loss as a complication of bacterial meningitis. RESULTS: Five patients had unilateral (n = 1) or bilateral (n = 4) contrast enhancement of vestibulocochlear structures. The structures most frequently involved were the cochlear nerve (n = 9), the first cochlear turn (n = 9), the vestibulum (n = 9), and the semicircular canals (n = 7). There was a significant correlation between clinical and MRI findings: all nine ears with cochlear enhancement were deaf (hearing loss >90 dB), whereas none of the five ears with normal MRI findings had hearing losses of more than 90 dB (range, 30 to 70 dB; p = 0.0005). Vestibular dysfunction as revealed clinically and by quantitative vestibular function testing was found in six of seven patients (11 of 14 ears). Five of these patients (nine ears) also demonstrated enhancement of the vestibular organ on high-resolution MRI of the inner ear. CONCLUSIONS: High-resolution MRI can visualize the involvement of vestibulocochlear structures in bacterial meningitis in both cooperative and consciously impaired patients. These findings suggest a correlation between abnormalities on MRI and the extent of cochlear dysfunction.

Adolescent↗
PubMed1999

[Improvement of hearing aid fitting with digital aids and new fitting strategies].

Hearing aids with digital signal processing demonstrate a large dynamic range with negligible distortion and no significant inherent noise. Furthermore, many acoustic parameters allow the compensation of even severe hearing loss, and the adjustment is extremely accurate. However, the new hearing aid generation not only requires computerized fitting, but also an experienced examination with new integrated fitting procedures. In addition to in situ measurement, the hearing aid fitting should include not only the Freiburg speech test, but also the Göttingen sentence test and the monosyllable rhyme test with different noises, for example the Fastl noise or the Döring babble noise. Loudness scaling with different methods is particularly important.

Analog-Digital Conversion↗
PubMed1999

Clinical utility of LDL-apheresis in the treatment of sudden hearing loss: a prospective, randomized study.

Although the pathogenesis of sudden hearing loss (SHL) is not as yet known, the clinical picture and the frequent association with vascular risk factors make an ischaemic event likely. This study aimed to assess the effect of an extracorporeal procedure (H.E.L.P.) in removing LDL-cholesterol, fibrinogen and lipoprotein (a) from the plasma, on the recovery of hearing SHL. This procedure using the HELP-system was compared with the usual standard treatment with prednisolone, dextranes and pentoxifyllin. We undertook a single centre, prospective, randomized study in which 18 patients were assigned to H.E.L.P.-apheresis and 9 patients were assigned to standard treatment (2:1 randomization). Audiometric and laboratory testing was performed at baseline, 24 h and 6 weeks after start of treatment. Primary endpoint was the improvement of the average pure-tone threshold between 0.125 and 8 kHz after 24 h. Twenty-four hours after H.E.L.P. treatment average pure-tone threshold recovered by 10.4 dB and by 26.4 dB after 6 weeks. The recovery of hearing of the standard treated patients was 5.8 dB and 16.8 dB after 24 h and 6 weeks respectively. LDL-cholesterol, fibrinogen and lipoprotein (a) were significantly reduced in the HELP treated patients compared with standard therapy, resulting in a significant improve in plasma viscosity, erythrocyte aggregation and resistance to oxidative stress of LDL particles. Our results suggest that the clinical outcome of SHL after a single extracorporeal LDL-apheresis is superior or at least equal to the more expensive standard treatment with prednisolone, dextranes and pentoxifyllin. Re-establishment of vascular endothelial function and improved blood rheology may be the underlying cause. These results must be confirmed in larger-scale trials.

Acute Disease↗
PubMed1999

Changes in serum osmolarity influence the function of outer hair cells.

Fast motility of outer hair cells (OHC) is thought to be based on a hydromechanic principle. In vitro, the function of OHCs can be disturbed by a change in the osmolarity of the culture medium. Whether changes in the serum osmolarity in vivo can also interfere with OHC motility has not been investigated as yet. Serum osmolarity of New Zealand White rabbits (n = 18) was elevated by a continuous infusion of glucose 40%, decreased by an infusion of aqua dest, or kept constant by an infusion of saline. OHC function was monitored using distortion products of otoacoustic emissions (DPOAE). Input output curves were established between 2 and 5 kHz (geometric mean of f2) with primaries of levels between 35 and 55 dB SPL. Cochlear perfusion was measured using a fluorescence microsphere method. Elevation of the serum osmolarity from 306 +/- 17 mosm/l to 365 +/- 23 induced a decrease of DPOAE between 3 and 12 dB SPL. Cochlear blood flow increased from 0.11 +/- 0.09 to 0.15 +/- 0.10 ml/min/g. When decreasing the serum osmolarity from 303 +/- 9 to 281 +/- 8 mosm/l, only slight changes of the DPOAE could be verified. As in the control group, cochlear perfusion was almost unchanged. In the control group, neither serum osmolarity nor DPOAE changed. Comparable to findings in vitro, increasing the serum osmolarity can lead to a disturbance of OHC function. In patients suffering from sudden hearing loss. dehydration due to physical or mental stress is often observed. This new and promising pathophysiological concept needs further clinical evaluation.

Acoustic Stimulation↗
PubMed1997

Lipid mixing in dimyristoyl phosphatidylcholine-dimyristoyl glycerol dispersions: spin label ESR studies.

The lipid transfer and mixing properties in hydrated dispersions of dimyristoyl phosphatidylcholine (DMPC)/dimyristoyl glycerol (DMG) binary mixtures have been investigated by using electron spin resonance spectroscopy of the spin-labelled lipid components. The assay system is based on the reduction in spectral broadening from spin-spin interactions that takes place by dilution of the spin-labelled lipid on transfer to a 9-fold excess of dispersions that contain no spin label. Lipid dispersions with DMPC:DMG compositions of 70:30, 40:60 and 20:80 mol/mol, for which the fluid phases have lamellar, inverted hexagonal and isotropic structures, respectively, have been studied. Essentially no transfer of spin-labelled lipid takes place for any of the lipid mixtures in the lamellar gel phase, or in dispersions of DMPC alone at all temperatures studied. The greatest degrees of transfer are found in the fluid phase of the DMPC/DMG mixtures. In general, the extent of lipid transfer is greater for the diacylglycerol component than for the phosphatidylcholine component. The extent of transfer of phosphatidylcholine is very low in the fluid lamellar phase of the 70:30 mol/mol DMPC/DMG, as compared with that of diacylglycerol. Only in the case of the 40:60 mol/mol DMPC/DMG mixture, in the inverted hexagonal phase, are the extents of transfer comparable for both phosphatidylcholine and diacylglycerol components, indicating a bulk transfer of lipid within the dispersions. The largest extent of transfer is found for diacylglycerol in the 20:80 mol/mol DMPC/DMG mixture in the isotropic phase.

Diglycerides↗
PubMed1997

Risk factors for early degeneration of allografts in pulmonary circulation.

OBJECTIVE: The aim of this study was to define risk factors for early degeneration of allografts in pulmonary circulation and to recommend some guidelines to minimize them. METHODS: Between January 1988 and March 1995, 202 patients with various types of congenital heart disease received cryopreserved allograft conduits for reconstruction of their right ventricular outflow tract. We report on 63 patients receiving allografts ranging from 9-24 mm size within the first 2 years of life. RESULTS: Survivors have been followed for 4-67 months. Survival at 5 years, including hospital mortality, was 66%. Two patients died at reoperation. Of the patients 19.6% (9/46) had early structural deterioration (SD) of their vascular allografts at a mean of 15.2 months after implantation. Seven of these have already been reoperated with allograft exchange. Freedom of reoperation was 66% at 5 years. Infants showed 48% freedom of reoperation at 5 years compared to 90% in the 1-2 years age group, while freedom of SD was 59% in infants at 48 months compared to 87% in the 1-2 years age group. Of allografts with SD in the infant group 66% had an allograft size of < 14 mm. In aortic allografts freedom of SD was 62% compared to 93% in pulmonary allografts. Freedom of allograft wall calcification was 46% at 18 months in all patients. In the statistical analysis, only infant age (P = 0.03) and aortic allograft (P = 0.02) were shown to be significant risk factors for early SD. CONCLUSION: The use of pulmonary allografts, avoidance of relatively short and small conduits of < 14 mm in diameter, might improve the durability of allografts in infants and small children.

Bioprosthesis↗
PubMed1997

[Possibility for quantitative and frequency-specific assessment of auditory threshold with otoacoustic emissions].

BACKGROUND: Otoacoustic emissions can be used to study cochlear function in a non-invasive manner. They are an effective clinical tool for infant hearing screening. The purpose of this study was to determine their utility for a frequency-specific and quantitative estimation of the hearing threshold. METHODS: Transiently evoked otoacoustic emissions (TEOAE) and distortion-product emissions (DPOAE) were recorded from 16 normal and 86 hearing impaired ears and correlated with their hearing threshold between 0.5 and 6.0 kHz. RESULTS: The correlations of TEOAE and the hearing threshold ranged from 0.53 (0.5 kHz) to 0.69 (6.0 kHz), of the DPOAE from 0.51 (0.5 kHz) to 0.83 (6.0 kHz). Based on the optimal correlating OAE frequency we tried to predict the hearing threshold. We obtained 95% prediction intervals for TEOA between 19 dB (1.0 kHz) and 39 dB (4.0 and 6.0 kHz), for DPOAE between 21 dB (1.0) and 34 dB (3.0 and 4.0 kHz). CONCLUSION: Despite their clinically irrelevant greater prediction intervals at the low frequencies, our results suggest that DPOAEs are generally more valuable for the frequency-specific estimation of the hearing threshold. Prediction intervals may improve the interpretation of OAEs.

Adolescent↗
PubMed1997

[Hypercholesteremia and hyperfibrinogenemia in sudden deafness].

BACKGROUND: The pathogenesis of sudden hearing loss has not been elucidated as yet. Insufficient perfusion of the cochlea due to an increased blood viscosity, microthrombosis, or altered vasomotion are assumed. Hypercholesterolemia and hyperfibrinogenemia are frequently observed in patients with sudden sensorineural hearing loss. The aim of this study was to investigate the incidence of hypercholesterolemia and hyperfibrinogenemia in patients suffering from sudden hearing loss compared to normal controls. In an intervention study the impact of drastic lowering of plasma cholesterol and fibrinogen by a selective extracorporal apheresis was studied. METHODS: In a case-control study of 23 patients suffering from sudden hearing loss, plasma cholesterol and fibrinogen levels as well as erythrocyte aggregation and plasma viscosity were determined. Seven sudden hearing loss patients from this group were treated with H.E.L.P. apheresis, an extracorporal procedure removing fibrinogen and idl-cholesterol from plasma. RESULTS: Plasma fibrinogen and cholesterol levels were higher in sudden hearing loss patients, leading to significantly elevated values of erythrocyte aggregation and plasmaviscosity. Six out of the seven patients treated with a single H.E.L.P. apheresis immediately showed an improvement of auditory thresholds. CONCLUSIONS: We conclude that hyperfibrinogenemia and hypercholesterolemia may contribute to the clinical event of sudden hearing loss. Our study shows for the first time that acute and drastic removal of plasma fibrinogen and low density lipoproteins can be an effective clinical tool in the treatment of patients with sudden hearing loss.

Adult↗
PubMed1997

[Reference curves for hearing surface scaling in clinical use].

METHODS: A commercially available system for the purpose of categorial loudness rating (WHF, WESTRA ELECTRONIC GmbH, Wertingen) was applied with 57 subjects with normal hearing to evaluate reference loudness level functions for 1/3-octave bandpass filtered noise and octave bandpass filtered environmental sounds. RESULTS: The procedure can be carried out with high reproducibility without effects of training due to repetition and only slight influence of subject sex, whereas the labeling of input device and temporal structure of the environmental sounds influence results, as does the center frequency. CONCLUSIONS: Our results showed deviations compared with the reference functions displayed in the WHF system.

Adolescent↗
PubMed1996

Lipid chain dynamics and molecular location of diacylglycerol in hydrated binary mixtures with phosphatidylcholine: spin label ESR studies.

The lipid chain motions in hydrated binary mixtures of dimyristoylglycerol (DMG) with dimyristoylphosphatidylcholine (DMPC) have been studied by using ESR spectroscopy of analogues of both components that are spin-labeled at one of eight different positions along the sn-2 chain. The phase diagram of the binary mixtures divides into three separate regions along the composition axis, corresponding to the formation of isothermally melting compounds, with DMPC/DMG stoichiometries of approximately 1:1 and 1:2 mol/mol in the gel phase [Heimburg, T., Wurz, U., & Marsh, D. (1992) Biophys. J. 63, 1369-1378]. In the first region (up to 50 mol % DMG), comparison of the chain flexibility profiles, and the chain profiles of the polarity-dependent isotropic hyperfine coupling constant, of the two different spin-labeled components indicates that DMG is incorporated in the fluid lipid bilayer in a manner similar to that of the host DMPC but is situated approximately two CH2 groups deeper into the hydrophobic interior. At lower contents of DMG, the chain packing is increased by the addition of DMG, whereas at higher DMG contents the lipid chain order decreases rapidly, on reaching the inverted hexagonal phase of the second region of the phase diagram. In the second region of the phase diagram (50-67 mol % DMG), the DMG fits better into the fluid inverted hexagonal phase than into the fluid lamellar phase of the first region and is located only approximately one CH2 group deeper than the corresponding DMPC. In these first two regions of the phase diagram, the ESR spectra of both spin-labeled components display an axial anisotropy that evidences the increasing angular amplitude of motion with position down the chain that is characteristic of liquid crystalline fluid phases. In the third region of the phase diagram (above 67 mol % DMG), the fluid phase consists of isotropically tumbling DMG molecules in which the DMPC molecules are incorporated as inverted micelles as indicated by the residual anisotropic motion of the spin-labeled phosphatidylcholine analogues.

Anisotropy↗
PubMed1996

Dynamic chain conformations in dimyristoyl glycerol-dimyristoyl phosphatidylcholine mixtures. 2H-NMR studies.

The dynamic molecular lipid chain conformations in fully hydrated dimyristoyl phosphatidylcholine (DMPC)-dimyristoyl glycerol (DMG) mixtures have been investigated by 2H-NMR spectroscopy of the individual lipid components, the sn-2 chains of which were perdeuterated or, in the case of DMG, specifically deuterated at the C-2 position. Mixtures of compositions corresponding to the three different regions of the binary phase diagram in which the fluid phase is lamellar (DMPC:DMG 70:30 mol/mol), inverted hexagonal (DMPC:DMG 45:55 and 40:60 mol/mol), or isotropic (DMPC:DMG 20:80 mol/mol) were investigated. The gel phase in all three regions of the phase diagram has a lamellar structure, with the lipid chains rotating about the molecular long axis but executing only limited angular excursions. In the fluid lamellar phase of the 70:30 mol/mol DMPC-DMG mixture the profile of segmental chain flexibility is similar to that in single-component phospholipid bilayers and is characterized by an order parameter plateau for both lipid components. The chain order of the DMPC component is greater than in bilayers of DMPC alone and is also greater than that of the DMG component. In the inverted hexagonal phase of the 45:55 mol/mol DMPC-DMG mixture the chain flexibility profile is characterized by more widely spaced segmental order parameters off the plateau region. The intrinsic degree of chain order in the inverted hexagonal phase is less than in the lamellar phase of the 70:30 mol/mol mixture, and the difference in chain order between the DMPC and DMG components is reduced relative to that in the lamellar phase. The unique conformational features at the C-2 position of the sn-2 chain that characterize bilayers of diacyl phospholipids are found also for the diacylglycerol molecules in the fluid lamellar phase and most probably also in the inverted hexagonal phase. The DMG molecules are therefore integrated in the membrane (or nonlamellar lipid phase) in a configuration that is similar to that of the phospholipids and different from the crystal structure of diacylglycerols.

Deuterium↗
PubMed1996

Evaluation of TEOAE and DPOAE measurements for the assessment of auditory thresholds in sensorineural hearing loss.

Transiently evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) can be quantified concerning their amplitude and frequency. They are known to be diminished or absent in sensorineural hearing loss. It is therefore of interest how TEOAE and DPOAE correlate with the auditory threshold and whether the auditory threshold can be predicted by these variables. In a cross sectional study of 61 patients (102 ears) with sensorineural hearing loss, auditory threshold, tympanometry, stapedius reflexes, TEOAE and DPOAE were measured. Correlation coefficients of the hearing loss (0.5-6 kHz) and the amplitude of the distortion product 2f1-f2 (0.46 4 kHz) respectively TEOAE amplitude (1-4 kHz) were computed. TEOAE showed lower correlation coefficients and less frequency specificity than DPOAE. In order to increase the correlations with the auditory threshold we fitted a multivariate linear regression model with TEOAE and DPOAE simultaneously as predictors for the auditory threshold gaining 95% prediction intervals of 19-39 dB depending on the frequency investigated. By restricting the hearing loss to a maximum of 70 dB HL the 95% prediction interval of the auditory threshold could be decreased to 18-26 dB. Further improvements can be expected if the high inter- and intraindividual variability of TEOAE and particularly DPOAE measurements can be reduced. The results allow us to use TEOAE and DPOAE in addition to click-evoked brainstem audiometry in order to provide more frequency specific information about the hearing loss in newborns, which is of the utmost importance for an ideal fitting of hearing aids.

Acoustic Impedance Tests↗
PubMed1995

Accelerated degeneration of allografts in the first two years of life.

Between January 1988 and May 1994, 53 of 159 patients have received cryopreserved aortic and pulmonary allografts for reconstruction of the pulmonary circuit in the first 2 years of life with body weight ranging from 2.2 to 18 kg (mean, 8.2 +/- 3.4 kg). The implanted allografts ranged in internal diameter from 9 to 23 mm (mean, 16.3 +/- 3.5 mm). Of the 38 survivors who regularly had postoperative echocardiographic examinations 15 (39.5%) underwent cardiac catheterization 1 to 31 months after operation. Allograft dysfunction (gradient > or = 50 mm Hg with or without pulmonary insufficiency) was confirmed in 9 patients leading to reoperation in 5 and valvulo-angioplasty in 4. At 48 months actuarial survival was 64%. In the aortic and pulmonary allografts freedom from wall calcification at 20 months was 19% and 100%, respectively. Freedom from valve dysfunction in patients with aortic and pulmonary allografts was 53% and 88%, respectively; it was 49% in allografts with an internal diameter of 17 mm or smaller. Freedom from reoperation in all patients was 78%. In conclusion, young age, antigenicity (ABO compatibility), and type of allograft seemed to be independent risk factors for early allograft conduit degeneration and late valve dysfunction. Pulmonary allografts seemed to be more resistant to early wall calcification and valve dysfunction than aortic allografts.

Actuarial Analysis↗
PubMed1995

[Screening program for selection of hearing loss in newborn infants instituted by the European Community].

Early identification of hearing impairment in children poses a major problem for clinical research and development. In the last two years we determined the hearing sensitivity of 1202 newborns, small infants and children. 52.4% of the children exhibited risk factors for hearing impairment in their medical history. The majority of children was referred to our department by pediatricians (52%), who first suspected hearing impairment, 40% by parents, 3.5% by otolaryngologists, 3% by educators, and 1.5% by general practitioners. The following examinations were performed: transiently evoked otoacoustic emissions (TEOAE), impedance audiometry, auropalpebralreflex, behavioral observation audiometry, and, if necessary, auditory brain stem response (ABR) with air and bone-conducted clicks as well as frequency-following responses at 500 Hz tone burst. In 378 children TEOAE were recorded on both sides, in 151 at least on one side. These results were confirmed by the other techniques. Only three children presented false negative results of TEOAE on one side. Two of these children had a middle ear effusion and a threshold of 35 dB, one had retrocochlear hearing loss. The absence of TEOAE in both ears in 155 children as well as in one ear in 16 children was detected by ABR. Seventy-seven patients showed no response on both sides, 25 on one side, although a hearing impairment more than 25 dB could not be verified by ABR. This high number of false positive results is explained in 77 cases (76%) by a middle ear dysfunction during the recording of TEOAE, when ABR was performed following adenotomy and paracentesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗