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T Lenarz

Publications and source records attributed to T Lenarz.

At least 19 recordsLinked to original sources
PubMed2006

[In vitro neurite outgrowth induced by BDNF and GDNF in combination with dexamethasone on cultured spiral ganglion cells].

BACKGROUND: The efficacy of cochlear implant performance depends, among many other factors, on the number of excitable spiral ganglion cells (SGCs) and the nerve-electrode interface. In earlier animal studies it has been demonstrated that neurotrophic factors are effective to improve SGC survival after experimentally induced deafness. With regard to their anti-inflammatoric and anti-proliferative effects, glucocorticoids (e. g. dexamethasone) are potentially interesting therapeutic agents to reduce connective tissue formation around the inserted electrode. The biological effects of a combined intervention of neurotrophic factors with steroids on SGCs are unknown. Therefore the objective of the study was to investigate possible trophic or even toxic effects of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and dexamethasone on neurite outgrowth of cultivated SGCs. METHODS: By using dissociated postnatal spiral ganglion cells (p3-5) for cultivation in the present study, the influence of the mentioned factors in various concentrations and combinations on neurite outgrowth of SGCs was analysed. RESULTS: Our results indicate significant trophic effects for BDNF (50 ng/ml) and a combination of BDNF with dexamethasone (100 ng/ml) on SGC neurite outgrowth. In contrast, single application of GDNF or dexamethasone in different concentrations caused no significant changes on neurite outgrowth when compared to the control condition. CONCLUSIONS: Neurite outgrowth induced by neurotrophic factors could not be observed to be reduced when dexamethasone is given at the same time. Therefore the demonstrated results provide a basis for further animal studies in this field of research.

Animals↗
PubMed2006

Normative auditory brainstem response data for hearing threshold in the rabbit.

In an experimental study, we determined the physiological hearing threshold of the rabbit in order to use these data as normative values for further experimental investigations. The aim was to use different acoustic stimuli (click and tone-pip stimuli) with different frequency spectra for air and bone conduction (BC) in order to obtain further information about the optimal form of stimulus when recording auditory evoked potentials in the rabbit. For the investigation, we used 46 female New Zealand rabbits weighing 3.2-4.4 kg and aged 6 months. The equipment used to record brainstem auditory evoked potentials was the Nicolet Viking IV P System (Nicolet Biomedical, Inc.). In accordance with the experimental set-up, the measurements took place under intubation anesthesia, with a total of four repeat measurements performed on each ear at different times. Tone-pip and click stimuli with varying intensities of stimulus, transmitted via air conduction and BC, were applied. The I-IV waves proved the most stable for both stimulus modalities. They were registrable in 98.7% of cases, whereas only 30.2% of the V waves could be recorded. Values averaged from all measurements made throughout the study yielded a potential threshold of 34.8 dB peak equivalent (p.e.) SPL for the click stimulus, 13.8 dB p.e. SPL for the tone-pip stimulus at 8 kHz and 34.2 dB p.e. SPL for the click stimulus transmitted via BC. With regard to latencies, the results indicated a good reproducibility through different stimuli with acceptable standard deviations. The values for physiological hearing threshold obtained here can serve as normative data in subsequent experimental animal studies.

Acoustic Stimulation↗
PubMed2006

[Parapharyngeal abscess and osteomyelitic destruction of the odontoid process].

We report the case of a 55 year old man with osteomyelitic destruction of the odontoid process and a parapharyngeal abscess. The patient was admitted with diagnosis of meningitis and degenerative cervical spine disease without compression of spinal cord or nerve roots but progressive impairment of cervical spine mobility. Inflammatory parameters in serum and cerebrospinal fluid were detected and antibiotic therapy was initiated resulting in subjective improvement of symptoms. When impairment of cervical spine motility persisted and gait disturbance developed, a parapharyngeal abscess and an osteomyelitic destruction of the odontoid process caused by infection with staphylococcus aureus was diagnosed. After cleavage of the abscess and four months of antibiotic therapy the gait disturbance disappeared and mild impairment of cervical spine motility persisted.

Anti-Bacterial Agents↗
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

[Neurotrophic factor expression in vestibular schwannoma. An overview].

The vestibular schwannoma is a benign, slow-growing neoplasm that originates from the neurolemmal sheath of the vestibular branch of the VIIIth cranial nerve. This tumor entity accounts for 6 % of all intracranial tumors and the annual incidence of newly diagnosed vestibular schwannoma is reported as 13 per million. The molecular pathogenesis of both sporadic vestibular schwannoma and those occurring in neurofibromatosis type II appears to be associated with an aberration of a tumor suppressor gene on chromosome 22q12. The biological background for the various growth patterns of vestibular schwannoma is, however, largely unknown. This differing clinical and biological behaviour of vestibular schwannoma may be explained by the presence of neurotrophic factors. The results of recent immunohistochemical studies demonstrate the co-expression of transforming growth factor (TGF)-beta 1 and glial cell line-derived neurotrophic factor (GDNF) in vestibular schwannoma and suggest a trophic synergism of both neurotrophic factors in this tumor. Moreover, expression of numerous different neurotrophic factors has been shown in studies of nerve growth factor (NGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), fibroblast growth factor (FGF), neuregulin (NRG) and erythropoietin (EPO) indicating a biological role in development, maintainance or growth of vestibular schwannoma. In this article, we summarize the findings on neurotrophic factor expression and discuss their characteristics and biological role in vestibular schwannoma.

Adult↗
PubMed2006

[Neurotrophic factors of the GDNF family and their receptors are detectable in spiral ganglion cells of normal hearing as well as of deafened rats].

BACKGROUND: Recent studies have shown that neurotrophic factors like BDNF, NT-3 and GDNF induce protective effects on spiral ganglion cells after noise- or drug-induced hearing loss. According to these studies it is suggested that deafness leads to a lack of neurotrophic factor or relating receptor expression in spiral ganglion cells, that has to be compensated by local cochlear application of these factors. METHODS: In the present study we examined the expression pattern of members of the GDNF family (GDNF, Neurturin, Artemin, Persephin) and their relating receptors (Ret, GFRalpha1 - 3) as well as BDNF and trkB on spiral ganglion cells of normal hearing and experimentally deafened rats (10 % neomycine). Indirect immunofluorescence was carried out to determine protein expression of these factors and their receptors 26 days following deafening. RESULTS: Our results demonstrate neurotrophic factor and receptor expression on spiral ganglion cells of normal hearing as well as experimentally deafened animals. CONCLUSIONS: Our data indicate that within a period of 26 days after deafening no detectable reduction of the GDNF-family member expression and their receptors was ascertainable on spiral ganglion cells by immunohistochemistry. Thus, a lack of neurotrophic factor expression is unlikely to be the only cause of spiral ganglion cell loss following deafening.

Animals↗
PubMed2006

[Paediatric cochlear implantation in the first year of life: preliminary results].

BACKGROUND: The success of cochlear implants in children was followed by a stepwise reduction in age at time of surgery. As a result of newborn hearing-screening (NHS) and the reliable audiologic diagnostic procedure, the question is raised as to whether an implantation before the age of 1 year is effective and safe in terms of surgery and rehabilitation. METHOD AND PATIENTS: This retrospective study included 27 children implanted before the age of 1 year (Gr. 1) and 89 children implanted between the age of 1 and 2 years (Gr. 2). Patient related data were analysed for individual history, surgery, rehabilitation and speech understanding. RESULTS: The incidence of complications was not increased in Gr. 1. The fitting of a speech processor was effective and uneventful in all children. The development of hearing and speech understanding showed better results after 2 years in Gr. 1. This development is more obvious for absolute age and not to rehabilitation time. CONCLUSION: In order to achieve an optimal timing for the development of speech understanding, cochlear implantation should be performed before the age of 2 years. This study revealed no additional risks for children in Gr. 1, but the development of speech understanding was better. As a consequence, cochlear implantation should be considered for very young children with an identified bilateral profound hearing loss.

Cochlear Implantation↗
PubMed2006

[Diagnosis and therapy of auditory synaptopathy/neuropathy].

Pathological auditory brainstem responses (lack of responses, elevated thresholds and perturbed waveforms) in combination with present otoacoustic emissions are typical audiometric findings in patients with a hearing impairment that particularly affects speech comprehension or complete deafness. This heterogenous group of disorders first described as "auditory neuropathy" includes dysfunction of peripheral synaptic coding of sound by inner hair cells (synaptopathy) and/or of the generation and propagation of action potentials in the auditory nerve (neuropathy). This joint statement provides prevailing background information as well as recommendations on diagnosis and treatment. The statement focuses on the handling in the german language area but also refers to current international statements.

Brain Stem↗
PubMed2006

[Embryonal rhabdomyosarcoma of the orbita].

A 2(1/2) year old girl was presented with an acute, painless orbital swelling without signs of local or systemic inflammation. CT and MRT scanning revealed a tumor which by open biopsy disclosed embryonal rhabdomyosarcoma. By means of this case we present the current diagnostic and therapeutic approaches for childhood soft tissue sarcomas. At present our patient receives a poly-chemotherapy which has already shown a good response. For local tumor control, a complete surgical resection as well as radiotherapy may be indicated and have to be considered carefully with respect to the possible late effects. This case demonstrates that in a child with a unilateral, progressive orbital tumor, the differential diagnosis of a soft tissue sarcoma has to be ruled out.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2006

[Expansion of an ceruminous adenoma into the middle ear].

A 37-year-old female presented for surgery with central perforation of the eardrum with granulation. Mastoidectomy had been performed 18 years ago following chronic mastoiditis. As the clinical picture now suggested a suspected cholesteatoma, radiological imaging was performed. The CT scan revealed specification of the mastoid and the tympanic cavity. In addition, MRI scan showed signal enhancement in the same areas. However, the suspected cholesteatoma could not be confirmed intraoperatively. Pathohistology revealed a ceruminal gland adenoma. They are a rare phenomenon and should be distinguished from middle ear adenomas, pleomorph ceruminal gland adenomas, ceruminal gland adenocarcinomas and cylindromas of the ceruminal glands. Owing to a high recurrence rate, complete surgical removal is necessary. Despite its rare occurrence, a ceruminal gland adenoma must be taken into consideration in the differential diagnosis of individual cholesteatoma cases.

Adenoma↗
PubMed2006

[Peripheral facial palsy as the first symptom of a metastatic bronchogenic carcinoma].

BACKGROUND: We present a case of a facial palsy as the initial symptom of a bronchogenic carcinoma. METHODS: Case-report. A 56-year-old patient presented with a peripheral facial palsy. The clinical picture as well as the temporal bone CT were without pathological findings. A 10-day rheologic therapy as well as anti-viral medication were not successful. Five days after rheological therapy had been completed, the patient presented a swelling of the neck. In the computer tomography we found a bilateral thrombosis of the internal jugular vein. In addition, the clinical picture of a left-sided glossopharyngeal palsy appeared. The following thorax CT as well as the diagnostic extirpation of an enlarged cervical lymph node lead to the diagnosis of a metastasized smallcell neuro-endocrine bronchogenic carcinoma with a compression of the right primary bronchus and the vena cava superior as well as an upper inflow congestion. In the cMRT we furthermore found a metastasis in the area of the foramen stylomastoideum. The patient underwent emergency radiation and chemotherapy. RESULTS: According to the present findings, this metastasis lead to the facial palsy as the initial symptom of the bronchogenic carcinoma. CONCLUSION: Therefore, therapy resistant facial palsy should be further diagnosed in detail, especially examined by imaging procedures.

Brain Neoplasms↗
PubMed2006

[Exostosis of the internal auditory canal in a patient with myotonic dystrophy].

A 53-year-old patient with myotonic dystrophy presented to our clinic with progressive bilateral hearing loss. The ENT status and particularly the otological examination were without pathological signs. Pure tone audiograms showed a bilateral moderate to severe sensorineural hearing loss. Routinely performed computed tomography of the temporal bones revealed the rare picture of exostosis of the internal auditory canals and the medial surface of the petrous bones. To our knowledge, this is the first report describing exostosis of the internal auditory canal in a patient with myotonic dystrophy, although at present it remains unclear in how far there is a causal connection between these two pathologies.

Audiometry, Pure-Tone↗
PubMed2006

In vitro measurement conditions for optical coherence tomography (OCT).

CONCLUSION: Tissue marking with soot-covered fine needles enables the optical coherence tomography (OCT) scanning plane to be localized within the histological specimen to an accuracy of approximately 50 microm. Tissue water content is an especially important parameter for in vitro measurements. Dehydration tends to produce an increase in surface reflections and a reduction in imaging depth. OBJECTIVES: The aim of this in vitro study was to evaluate parameters relevant to the visualization and conservation process to allow optimal images to be generated for later differentiation between healthy and degenerated tissue in vivo. MATERIALS AND METHODS: Various methods of marking samples were applied in vitro to achieve accurate overlaps of the OCT scanning plane and the corresponding section of the histological specimen. The influence of temperature and tissue water content was investigated using both porcine and human tissue. Samples were marked using fine needles, ablation craters generated by laser application, and colour markers introduced into the tissue. RESULTS: It was demonstrated that the water content of tissue exerts a direct influence on OCT imaging, whereas above 15 degrees C temperature had no effect on image quality. With regard to the marking of samples, the best results were obtained using sooted fine needles.

Adipose Tissue↗
PubMed2005

Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5-0.6.

Action Potentials↗
PubMed2005

[Malignant transformation of a juvenile papilloma in a 11 year old boy].

BACKGROUND: The juvenile laryngeal papilloma is the most common benign neoplasm in children. Often the entity shows an elongated recurrent course of disease with an expansion into the tracheo-bronchial system. Sporadic malignant transformation in adults with a papilloma was reported after treatment with radiotherapy alone or in combination with the intake of additional toxins (e. g. nicotine). Similar reports of a malignant transformation of juvenile papillomas without additional risk factors is very rarely reported. CASE REPORT: We report about an 11 year old boy, who suffered from a juvenile laryngeal papilloma. The multiple laser surgical procedures and a therapy with interferon resulted in a short-term remissions. A tracheotomy was inevitable. Seven months after the first diagnosis of the papilloma a regional metastatic squamous cell carcinoma was found. In spite of combined radiotherapy and chemotherapy the boy died 11 months later. CONCLUSIONS: The spontaneous malignant transformation of a juvenile papilloma in a squamous cell carcinoma is extremely rare. The surgical intervention as well the radiotherapy and chemotherapy using interferon was unsuccessful due to the high grade of malignancy. In view of the very short time interval between first diagnosis of juvenile papilloma and the subsequent malignant transformation, one must consider either the potential presence of a very aggressive form of papilloma or alternative two coincident independent diseases.

Antineoplastic Agents↗