Biomedical subjects

Jan Maurer

Publications and source records attributed to Jan Maurer.

12 recordsLinked to original sources

PubMed2005

Vascular endothelial growth factor expression, vascularization and proliferation in paragangliomas.

OBJECTIVE/HYPOTHESIS: Paragangliomas are heavily vascularized tumors, and the expression of VEGF (vascular endothelial growth factor) has been reported. The aim of our study was to extend the available database of VEGF expression in paraganglioma, to add correlated data concerning vessel density and proliferative activity, and to draw conclusions concerning the mechanisms resulting in tumor vascularization and growth. STUDY DESIGN: Semiquantitative histopathologic examination of paraganglioma specimens obtained from surgical cases. METHODS: Paraffin-embedded paragangliomas were analyzed by immunohistochemistry. Fourteen consecutive samples were hybridized with VEGF-, CD31- and Ki67-specific antibodies, and visualized by diaminobenzidine staining. Vessel density was determined by counting CD31-positive vessels and proliferation by quantification of Ki67-positive cells. RESULTS: Ten out of 14 samples were positive for VEGF. In this group, vessel density was up to 5 times as high and proliferative activity was about twice as high as in the VEGF-negative group. CONCLUSIONS: We observed higher CD31 and Ki67 counts in VEGF-positive tumors, but statistical significance could not be assessed due to low sample numbers. These data might suggest a contribution of VEGF secreted by paragangliomas to tumor vascularization and possibly proliferation. The clinical impact of VEGF expression analysis has to be proven in future studies.

Adult↗

PubMed2005

Steroid and vasoactive treatment for acute deafness after attempted hearing preservation acoustic neuroma surgery.

OBJECTIVE: To investigate whether intravenous steroid and vasoactive therapy in the acute postoperative period improves hearing outcome in patients who develop acute deafness after attempted hearing preservation surgery for acoustic neuroma (AN) through a retrosigmoid or a middle cranial fossa approach. STUDY DESIGN AND SETTING: Retrospective controlled study in a tertiary care center. Thirty-six patients who had developed acute deafness after hearing preservation surgery for treatment of an AN were reviewed. Preoperative AAOHNS hearing class was A in 2, B in 2 and D in 32 patients. Twenty-seven patients were treated with prednisolone, hydroxyethyl starch 3% and pentoxifylline intravenously for a period of at least 5 days. Nine patients (controls) did not receive any specific steroid or vasoactive therapy. RESULTS: All patients in both groups remained deaf. CONCLUSIONS: Intravenous therapy with prednisolone, hydroxyethyl starch 3% and pentoxifylline in the acute postoperative period does not improve hearing in patients who develop acute deafness after attempted hearing preservation surgery for AN.

Acute Disease↗

PubMed2005

DPOAE-grams in patients with acute tonal tinnitus.

OBJECTIVE: To investigate cochlear outer hair cell function in patients with acute tonal tinnitus and normal or near-normal hearing threshold. STUDY DESIGN AND SETTING: Prospective controlled study in an academic tertiary health center. Distortion products of otoacoustic emissions (DPOAE)-grams of 32 ears with acute tonal tinnitus and normal hearing or minimal hearing loss were compared with those of 17 healthy nontinnitus ears. RESULTS: Tinnitus ears exhibited relatively increased amplitudes of DPOAE at high frequencies (4-6.3 kHz) when compared with the group of healthy ears and relatively decreased DPOAE amplitudes at middle frequencies (1650-2400 Hz). Statistically significant ( P < 0.01) increased mean values of DPOAE amplitudes were observed only at a frequency of f2 equal to 4.9 kHz. CONCLUSIONS AND SIGNIFICANCE: These findings suggest an altered functional state of the outer hair cells at a selected high-frequency region of the cochlea in ears with acute tonal tinnitus and normal or near-normal hearing threshold.

Acoustic Stimulation↗

PubMed2005

Reliability of cochlear implants.

BACKGROUND: The long-term reliability of cochlear implants over time is an important issue for patients and cochlear implant teams. The calculation of cumulative survival rates including all hard failures of cochlear implants is suitable to report objectively about cochlear implant reliability. METHODS: This is a report of 192 cochlear implants from different manufacturers in adults (n = 58) and children (n = 134). RESULTS: The overall cumulative implant survival rate was 91.7% for a period of 11 years. The main reasons for hard failures were design errors of the products and direct or indirect trauma to the cochlea implant site (especially in children) with consecutive breaks of the implant body or electrodes. CONCLUSIONS: To improve our knowledge about reliability of cochlear implants more studies on cumulative long time survival of cochlear implants are needed, where functional failures and complications for whatever reason (design, mechanical, electronic, medical) are included. Cochlear implant reliability data should be considered during the choice of an implant for each individual patient.

Adult↗

PubMed2005

Epidural hematoma after cochlear implantation in a 2.5-year-old boy.

OBJECTIVE: Report a case of an epidural hematoma after cochlear implantation in a 2.5-year-old boy, the diagnostic and therapeutical emergency management, as well as the postinterventional course and rehabilitation of the child. STUDY DESIGN: Retrospective case review. PATIENT: Two and a half-year-old boy, suffering from early onset, profound sensorineural hearing loss had been diagnosed at an age of 1.5 years, which had been more severe on the right side initially, but had progressed to bilateral deafness. INTERVENTION AND COMPLICATION: Cochlear implantation on the left side, followed up by an extensive epidural hematoma, causing intracranial compression with a midline shift of 15 mm to the right side. This initial complication was followed up by arterial infarction not only of the middle but also the posterior as well as the anterior cerebral artery, most likely caused by incarceration through the tentorium. RESULTS: After immediate neurosurgical intervention and intensive care treatment including low-dose anticoagulation and high doses of corticosteroids, the child recuperated completely within 3 weeks without any remaining neurologic deficits. CONCLUSION: In cochlear implantation, especially if placement of the implant housing is associated with considerable bone work, epidural hematoma has to be considered as an extremely rare, but life-threatening, complication.

Child, Preschool↗

PubMed2004

Long-term results after interval therapy with intratympanic gentamicin for Menière's disease.

OBJECTIVES: The new single-shot and interval treatment for Menière's disease with gentamicin was designed to avoid cochlear damage during treatment with gentamicin. METHODS: To date, 90 patients were treated with the single-shot or interval gentamicin therapy. Fifty-seven cases of Menière's disease were followed up prospectively between 2 and 4 years. During one treatment series, a maximum of three intratympanic gentamicin injections within 15 days were applied, each consisting of 0.3 mL (12 mg) of gentamicin (days 1, 8, and 15). Thirty of these 57 patients (53%) needed only one injection to be controlled (single-shot treatment). RESULTS: Vertigo attacks were completely controlled in 95% and partially controlled in 5%, whereas hearing remained unchanged or even improved. Tinnitus as well as aural fullness were controlled in approximately 50% of the cases. CONCLUSION: Our results with this group of patients after interval-treatment or single-shot application of intratympanic gentamicin demonstrate the effectiveness of this treatment modality with very low side effects, and, although our experience is still limited, it allows for expanding the indication on early cases of Menière's disease before permanent hearing loss occurs. Even cases of bilateral Menière's disease can be treated successfully using this method. Cochleotoxic side effects can be prevented by treatment intervals of 7 days.

Anti-Bacterial Agents↗

PubMed2003

Evidence for a possible NOS back-up system in the organ of Corti of the guinea pig.

Recently, the two Ca(2+)/calmodulin-regulated nitric oxide synthase isoforms, nNOS and eNOS, and NO itself have been identified in the cochlea of vertebrates using specific antibodies and a new fluorescence indicator. In order to acquire more information about the quantitative and spatial distribution of these two constitutively expressed NOS isoforms (cNOS) in the organ of Corti at the cellular and subcelluar levels, ultrathin sections of London resin (LR) White-embedded cochleae of the guinea pig were incubated with various concentrations of commercially available antibodies to nNOS and eNOS. The immunoreactivity was visualized by a gold-labeled secondary antibody and the amount of the immunoreactions/microm(2) was quantified for different cell types and subcellular regions. Both NOS isoforms were identified to varying degrees in the same cell types and subcellular regions. A prominent eNOS immunoreactivity was identified in nearly every cell type. In all analyzed animals the highest number of gold-coupled anti-eNOS antibodies was always seen in the cells of the reticular lamina, especially in the cuticular structures of outer and inner hair cells, pillar cells and apical Deiters' cells. Also the microtubuli-containing cytoplasmic regions of Deiters' cells were scattered with gold-coupled anti-eNOS antibodies. A clear eNOS immunoreaction was also found in the remaining cytoplasm of inner and outer hair cells and in the apical Deiters' cells. Numerous anti-nNOS antibodies were located in the outer hair cells and in the cuticular structures of the apical Deiters' cells. The amount of the gold-labeled anti-nNOS antibodies in the cuticular plates of the pillar cells and outer hair cells and in the cytoplasm of inner hair cells and apical Deiters' cells were clearly less but still above unspecific background labeling. The spatial co-localization of the two NOS isotypes in the same cell regions was proven in double-labeling experiments. The spatial distribution of the two cNOS isoforms confirmed recent findings of other authors who localized NO distribution and production sites. The cNOS co-expression with similar function in the same cell type and subcellular regions may represent a functional "back-up system" in which one NOS isoform can replace the other in case of pathophysiological malfunction.

Animals↗

PubMed2003

Expression of angiogenic growth factors in acoustic neurinoma.

OBJECTIVES: Acoustic neurinoma (AN) can grow to a large size, but the growth-promoting molecular pathways remain unknown. As angiogenesis has been described as being activated in many cancers, we undertook this study in order to examine the microvascular network of AN and the expression of angiogenic growth factors and their cognate receptors in AN. The aim was to draw conclusions regarding the underlying mechanisms and potential benefit of a pathway-specific anticancer therapy. MATERIAL AND METHODS: Surgical specimens from 34 patients with AN were analysed immunohistochemically for the expression of vascular endothelial growth factor (VEGF), VEGF-receptor 1 (VEGF-R1), VEGF-receptor 2 (VEGF-R2) and transforming growth factor-beta1 (TGF-beta1). The microvessel density (MVD) was defined using CD31 staining and macrophage infiltration using CD68 staining. MVD was correlated to tumour size, patient age and duration of symptoms. RESULTS: With 1 exception each for VEGF and VEGF-R1, none of the 34 tumours expressed either VEGF, TGF-beta1, VEGF-R1 or -R2. No tumour-infiltrating macrophages were detected. The MVDs determined were low and did not correlate with tumour size, duration of symptoms or patient age. CONCLUSION: These findings indicate that ANs either do not express or express very low levels of the analysed proangiogenic growth factors. We conclude that tumour angiogenesis is not likely to be a relevant mechanism of AN growth and might therefore not be a suitable anticancer therapy target.

Adult↗

PubMed2003

Localization of the two constitutively expressed nitric oxide synthase isoforms (nNOS and eNOS) in the same cell types in the saccule maculae of the frog Rana pipiens by immunoelectron microscopy: evidence for a back-up system?

There is growing evidence for a nitric oxide/cyclic GMP pathway of signal transduction in the vestibular system. Recently, two isoforms of nitric oxide (NO) synthase (nNOS and eNOS) and NO itself have been identified at the light microscopic level in the vestibulocochlear system of mice using specific antibodies and a new fluorescence indicator. In order to acquire more information about signal transduction and tissue modulation in this neuroepithelium at the cellular and subcellular levels, ultrathin sections of London Resin White-embedded saccule maculae of the frog Rana pipiens were incubated with various concentrations of commercially available antibodies to nNOS and eNOS. The immunoreactivity was visualized by a gold-labelled secondary antibody and the amount of the immunoreactions per microm2 was quantified for the different cell types and subcellular regions. Significant eNOS immunoreactivity was identified in the hair bundles, cuticular plates and the rest of the cytoplasm of the hair cells as well as in different subcellular regions of the supporting cells. Gold-labelled anti-nNOS antibodies stained mainly stereovilli and cuticular structures of hair cells and supporting cells, whereas the number of the immunoreactions in the remaining cytoplasm of both cell types was near the background level. The spatial co-localization of the two NOS isotypes in the same cell regions of hair cells and supporting cells was confirmed in double-labelling experiments. The immunocytochemical findings are suggestive of a redundant system in which one NOS isoform can (partially) replace the other. The different subcellular localization of the NOS isoforms may allow for isoform specific regulation of NOS activity by different Ca2+ currents at the subcellular level, underlining the importance of NO-regulated processes in neuroepithelia of the inner ear.

Acoustic Maculae↗

PubMed2003

Association of proliferative activity and size in acoustic neuroma: implications for timing of surgery.

OBJECT: Acoustic neuroma is the most frequent benign tumor of the cerebellopontine angle, and surgery is still the most common form of treatment. To gain better insight into the dysregulated mechanisms causing growth of acoustic neuroma, the authors studied the proliferative activity of 34 consecutive samples by analyzing immunohistochemical staining with Ki-67 and proliferating cell nuclear antigen (PCNA), and apoptosis based on the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. Data from these analyses were correlated with clinical parameters (that is, tumor size, duration of symptoms, and patient age). METHODS: Apoptotic cells were found in none of the tumors. Proliferation measured on staining with Ki-67 and PCNA correlated with tumor size, but not with patient age or duration of symptoms. The authors demonstrated that tumors 18 mm or smaller in diameter have lower proliferation indices and growth rates, compared with tumors larger than 18 mm with high proliferative indices and growth rates. Additionally, they observed that these more aggressive, larger tumors occur mostly in patients younger than 50 years of age. CONCLUSIONS: Patients with tumors larger than 18 mm in diameter and who are younger than 50 years of age sustain an enhanced risk for fast-growing tumors because of these lesions' enhanced proliferative activity. For these patients the authors recommend active therapy.

Adult↗

PubMed2002

Auditory late cortical response and speech recognition in Digisonic cochlear implant users.

OBJECTIVE: The purpose of the study was to test for differences in late electrically evoked auditory potentials between subjects exhibiting "good" versus "poor" speech recognition performances with their cochlear implants. METHODS: Late auditory evoked responses were measured in 30 subjects equipped with the Digisonic (MXM, Antibes, France) cochlear implant, 15 of whom had "good" speech recognition scores (i.e., more than 89% correct phoneme identification without lip reading). The 15 other subjects had poorer speech recognition scores (i.e., less than 85%). RESULTS: Differences in N1P2 amplitude, as well as P1, N1, and P2 latencies, and N1-P1 and N1-P2 latency intervals were tested. Wave P2 latency was found to be significantly different between the two groups (P =.016), being shorter in "good" than in "poor" performers. The strength of the statistical relationship between electrophysiological and speech recognition variables (r2 = 17%) was substantially smaller than that observed using electrically evoked auditory brainstem response (EABR) for the same implanted device (r2 = 49% for the EABR wave III-V latency interval). CONCLUSIONS: Some characteristics of late electrically evoked auditory potentials differ significantly among cochlear implant users depending on their speech recognition performance. However, the relationship between electrophysiological and speech recognition variables is more pronounced when early (brainstem) rather than late (cortical) evoked responses are considered.

Adult↗

PubMed2002

Vestibular function after acoustic neuroma removal with preservation of one branch of the vestibular nerve.

BACKGROUND: Vestibular compensation after acoustic neuroma surgery is affected by many parameters. Apart from surgical approach, age of the patient, and comorbidity, the use of rehabilitative vestibular training and the degree of preoperative vestibular compensation play their respective roles. OBJECTIVE: To examine whether and how surgical preservation of one branch of the vestibular nerve affects the compensation process in patients after acoustic neuroma removal. STUDY DESIGN: Prospective study involving 29 patients with acoustic neuromas. In 15 patients operated on by the middle fossa or retrosigmoid approach, one branch of the vestibular nerve could be preserved intraoperatively, and the course of the compensation process was followed (Group 1). Fourteen other patients with acoustic neuroma, who were operated on via a translabyrinthine approach, served as a control group (Group 2). MAIN OUTCOME MEASURE: The evaluation of vestibular compensation was accomplished clinically, by electronystagmography, and by dynamic posturography. RESULTS: An accelerated vestibular compensation was found in all examinations for Group 1, and 3 months after surgery 47% of the patients in this group were back to work without substantial restrictions, compared with 29% of Group 2. At the end of 6 months, however, there was no more significant difference between the two groups. CONCLUSION: The long-term results of vestibular compensation do not seem to be influenced by partial preservation of the vestibular nerve, whereas the compensation process seems to be accelerated when the nerve is partially preserved.

Electronystagmography↗