Biomedical subjects

P Düwel

Publications and source records attributed to P Düwel.

7 recordsLinked to original sources

PubMed2005

[Towards a cellular pathophysiology of Meniere's disease].

BACKGROUND: A modest increase in the hydrostatic pressure within the endolymphatic space may induce an endolymphatic hydrops which in turn is typically associated with Meniere's disease. However, there is no convincing pathophysiological model that might explain, on a cellular level, how a pressure increases may cause disturbed functions of vestibular hair cells and vertigo attacks. METHODS: So far, models involve osmotic mechanisms leading to electrolyte imbalances in the endolymphatic space. Alternatively, impaired longitudinal flow in the endolymphatic space is considered important. RESULTS: Recently, a pressure-sensitive potassium current was identified and characterized in vestibular hair cells. CONCLUSIONS: This current may modify the frequency behavior of a cell and may be the "missing link" in a cellular pathophysiology of the hydrops. Ion currents in hair cells offer attractive targets for pharmacological interventions in Meniere's disease.

Calcium↗

PubMed2005

[Time-dependent vestibular function loss of semicircular canals and otolith organs in Menière's disease].

INTRODUCTION: Since Dohlmann's investigations the extremely variable interindividual natural course of Menière's disease has been documented. The description of sub-entities of Menière's disease shows, the localisation of dysfunction within the labyrinth is of considerable importance. The selective investigation of crista and macula sensor organs and its time-dependent progression even provides information for the disease's staging. METHODS: In the retrospective trial presented here, 126 patients suffering from vertigo were tested by the methods described above. 10 of these patients who showed a triad of symptoms including vertigo attacks, unilateral sudden hearing loss and tinnitus were selected for this study. All 10 patients were tested within 48 hours after the last acute vertigo attack by means of caloric irrigation and VEMPs. RESULTS: The function loss verified in saccular testing could be found in Menière's disease progression at an earlier stage than the utricular function loss. Most patients with a long history of vertigo attacks also suffered from a dysfunction of the semicircular canals. DISCUSSION: The differential testing of the otolith function is a valid tool for the recognition of early labyrinth dysfunction in Menière's disease and could lead to an earlier onset of specific therapy. It also provides the base for a differentiated staging prior to therapy planning.

Adolescent↗

PubMed2005

[Otolith function tests--a differentiated, quality-assured screening system].

INTRODUCTION: More than 30% of all otogenic vestibular disorders are related to isolated macular dysfunction. Videooculographic examination techniques for the otolith-ocular reflex, e. g. by means of eccentric rotation tests, are not widely used in clinical routine as these put a considerable strain on technical and staff resources. Thus, there is a considerable risk of "false negative" classification of vertigo disorders being labelled as "non-otogenic". By means of vestibular-evoked myogenic potentials (VEMPs) and caloric irrigation in prone and supine position, several examination techniques for a side-related investigation of macula-induced vestibulo-ocular reflexes are available. The objective of this study is to compare and evaluate these techniques as screening tests. METHODS: In 32 patients with vestibular disorders we performed investigations for VEMPs, eccentric rotation tests, as well as caloric irrigation for macular reaction in prone and supine position. In addition, we performed other audiologic and vestibular function tests which were complemented by the clinical course in order to differentiate each case between otogenic and non-otogenic vertigo with or without macular affection. RESULTS: The technical feasibility as well as patients' acceptance for VEMP testing is better than for eccentric rotation tests. The sensitivity index for VEMPs (89%) as well as for caloric irrigation in prone and supine position for macular examination (71%) is satisfactory. However, the specificity of VEMPs is inferior (53%) to eccentric rotation (100%). DISCUSSION: Both the examination for VEMPs as well as caloric macular testing in prone and supine position carry features which make them feasible for screening, even though these two procedures test for two different parts of the otolith system. However, to confirm a diagnosis and to set up a therapeutic concept for macular function disorders, eccentric rotation should be added.

Caloric Tests↗

PubMed2003

Potassium currents in vestibular type II hair cells activated by hydrostatic pressure.

An elevated hydrostatic pressure in the endolymphatic space of the inner ear is discussed as pathophysiological factor in hydrops-related diseases of the inner ear. An increase in pressure by fractions of 1 cm H(2)O is sufficient to induce vertigo-like symptoms in animal models. To establish a link between hydrostatic pressure and the function of vestibular hair cells, we studied potassium currents in isolated vestibular type II hair cells from guinea-pig utricles when the hydrostatic pressure was increased by raising the height of the bath from 0.2-0.5, 0.7 or 1.0 cm. Elevated pressure enhanced K(+) currents significantly; a rise in pressure from 0.2-0.5 cm H(2)O increased the total K(+) current at +40 mV by 22+/-14% (+/-S.D.). The pressure-sensitive current I(K,p) was non-inactivating during depolarizing pulses. It was maintained when the pressure was kept elevated for several minutes and receded promptly after return to a pressure of 0.2 cm H(2)O. Voltage-gated Ca(2+) currents, in contrast, were not altered by hydrostatic pressure. A pharmacological characterization of I(K,p) revealed that tetraetylammonium (100 mM) abolished all outward currents including I(K,p). I(K,p) was partly and reversibly inhibited by 4-aminopyridine. Dihydrostreptomycin, a blocker of the transduction channel, left I(K,p) unaffected. Charybdotoxin (100 nM), a blocker of Ca(2+)-dependent K(+) channels, completely yet reversibly abolished I(K,p). We conclude that small elevations in hydrostatic pressure evoke a charybdotoxin-sensitive, probably Ca(2+)-dependent K(+) current in vestibular hair cells. This is likely to alter their frequency response and may be a relevant mechanism how hydrostatic pressure disturbs transduction.

Animals↗

PubMed2003

[Testing of the macula induced vestibuloocular reflex--possibilities and problems in the clinical routine].

INTRODUCTION: During the last years, an increasing number of papers is presented dealing with diseases and diagnostic procedures of the macula function. On the other hand, there are just a few distinct test setups for this purpose. In clinical routine, this kind of test system has to be efficient and effective to diagnostic and therapeutic findings. METHODS: The presented test setup includes examination of the semicircular canals by means of harmonic acceleration pendular rotation test and the bilateral, bithermal test as well as otolith function tests i. e. off vertical axis rotation (OVAR) and eccentric rotation. From March 1999 to May 2000 522 patients with dizziness were examined. RESULTS: Otolith tests results could be assessed in a range between 87 % to 95 % of the cases. The quality failure rate was significantly higher than in findings of semicircular canals examination procedures. The major caused technical problem were artifacts. Looking for the diagnostic relevance of the method, 37 % of the patients. Suffering from dizziness and who have normal findings in cupula VOR testing procedures revealed isolated macular dysfunctions. DISCUSSION: The relevance for diagnostic is demonstrated. Otolith function tests can be applied in clinical routine and give relevant information for diagnosis and treatment. Macula test procedures are still sophisticated. Technical development of VOG-recording is necessary for their general application in otology.

Acoustic Maculae↗

PubMed2002

[Vestibular diagnostics in childhood - methods and assessment].

BACKGROUND: Children with vertigo are thought to be difficult to examine. Vestibular test batteries are used less frequently for children than in adult patients. METHODS: Within the context of a retrospective study 136 patients in age between 0 and 15 years, who were examined by Frenzel's glasses, ENG and VOG between 1996 and 1999 were evaluated. Caloric test and frequency selective rotation chair tests were performed. RESULTS: Workability of VOG examination (91 %) was higher than Frenzel glasses (86 %) and ENG (78 %). Videooculography is the method of choice in childhood. Comparing diagnosis after vestibular testing and discharge diagnosis a sensitivity of 68 %, a specificity of 88 %, an accuracy of aim of 79 % and a positive predictive value of 92,9 % was calculated. CONCLUSION: Thus restriction of vestibular functional diagnostics in childhood is not justified.

Adolescent↗

PubMed2001

[Magnetic resonance tomography imaging of the inner ear of patients with sensorineural hearing loss or vertigo].

BACKGROUND: Progress in surgical techniques in the temporal bone has lead to the demand of exact delineation of this complex anatomical region for preoperative planning. The aim of this study was to assess the potential of a three-dimensional T2 weighted turbo-spin-echo-sequence to depict anatomical details and pathological changes of the inner ear. METHODS: Twenty-five patients presenting with sensori-neural hearing loss and/or vertigo were included in this study. A T2 weighted turbo-spin-echo-sequence was carried out on a 1.5 T imager, employing a surface coil with a diameter of 8 cm. The scan parameters were set as follows: TR 2000, TE 500, scan matrix 128 x 128, field of view 90 mm, slice thickness 0.66 mm, NSA 4. In addition, 3D maximum-intensity-projections (MIP) were created, using these data as source images. RESULTS: Image quality was excellent in all 25 cases. The 2.5 cochlear windings, modiolus, vestibule with saccule and utricle all three semicircular canals, crus commune and the facial nerve and vestibulocochlear nerve in the inner auditory canal were clearly delineated in all patients. The cochlear aqueduct was seen in 32% (8 cases), while the vestibular aqueduct was delineated in 16% (4 cases) in this series. In MIP, the entire labyrinth was shown in a single view. In 22 patients regular morphology was found, while in three cases pathological changes were detected (an enlarged vestibular aqueduct and saccus in one patient, partial fibrous obliteration of the labyrinth in two patients). CONCLUSIONS: The introduced TSE sequence can be used to delineate the anatomy of the inner ear as well as pathological changes. The technique appears to be useful for preoperative planning.

Adolescent↗