Biomedical subjects
Publications and source records attributed to T Lenarz.
A harpoon-shaped electrode was positioned to the nasopharynx through the nose for registration of BERA-potentials. The amplitudes of peak IV and V increase without changes of latencies. Potential IV is clearer for evaluation of the central conduction time in cases with a single IV/V-complex. Mechanisms of amplitude pattern changes are discussed.
We report on two patients with sudden hearing loss occurring immediately after registration of an acoustically elicited acoustic reflex with pure tones of 500, 1000, 2000, and 4000 cps and 125 dB HL. Aetiology and patho-physiology of this form of acute acoustic trauma are discussed. An obvious destruction of middle ear structures or the membrane of the round and oval window can be excluded. Assuming pre-existing disposition, e.g. distortion of microcirculation in the cochlea, the acoustic stimulus is merely the trigger for the imminent sudden hearing loss. Therefore, we suggest to limit the stimulus power to 105 dB HL. In every case one should keep in mind the possible danger of this examination and perform a benefit-risk calculation in every patient.
The present examination shows the action of the acoustic reflex on stimulation with a pure tone of 500 cps which lies 10 dB above the reflex threshold by impedance measurement. The duration of stimulation lasts 5 min. The test results of persons with normal hearing, persons with cochlear and retrocochlear lesions were measured according to the amount, the duration, the beginning, and the speed of reflex decay. The preliminary results permit the following conclusions: Persons with noise-induced hearing loss show no reflex decay for the entire duration of stimulation. Persons with normal hearing show a reflex decay after 2 min. After another 135 sec a constant reflex amplitude is attained. Subjects with cochlear lesions which are not caused by noise show similar reflex behavior. The amount of decay is larger, and the decay begins earlier. Persons with retrocochlear lesions show heterogeneous results, but the average amplitudinal decay is rapid and exceeds 50 per cent. The underlying mechanisms are discussed. In our opinion muscle fatigue plays an important role, which is absent in noise-induced hearing loss due to a permanent muscle training caused by the chronic noise exposure. The main result for audiology lies in the possibility to distinguish clearly between noise-induced hearing loss and other forms of cochlear lesions.
In 22 patients with acute myocardial infarction, intracoronary infusion of streptokinase was begun 3.2 +/- 1.4 hours after the onset of symptoms. In 71% of patients recanalization of a completely occluded artery could be achieved. In 12 successfully treated patients left ventricular hemodynamics (left ventricular diastolic compliance and regional wall motion) were compared before and 4 weeks after recanalization. 4 weeks after intracoronary fibrinolysis left ventricular end-diastolic pressure had fallen (from 20 to 15 mm Hg, p less than 0.05), diastolic compliance had improved (p less than 0.05) and infarct size was reduced (p less than 0.05) compared to the acute stage of myocardial infarction. Left ventricular hemodynamics of 16 patients without heart disease (group A) and 22 patients with chronic myocardial infarction treated medically (group B) were compared to the findings of patients with acute myocardial infarction (group C). Group B and C showed reduced diastolic compliance as compared to group A (p less than 0.001). When group B and c were compared with identical size of akinesis (as measured by the number of asynergic hemiaxes), there was no significant difference of diastolic compliance. Reduction of diastolic compliance correlated linearly with infarct size (r = 0.73, r = 0.78). The results indicate that successful early reperfusion of acute myocardial infarction leads to a reduction of infarct size.
The objective of this study was to develop a method of cement microapplication using glass-ionomeric cement. The results of an experimental study to design a microapplication method of glass-ionomeric cement (Ionocem) are presented. Typical middle ear implant materials, as well as human temporal bones and middle ear ossicles, were used to test the efficiency of this application method. Two different versions of Ionocem, low and normal viscosity, were tested under different temperatures and with several application tools. Sufficient processing time could be achieved by cooling the cement down to 4 degrees C. A subcutaneous insulin syringe with a milled-off tip proved to be cost-effective, efficient and versatile. Using this instrument, durable and secure cementation between the parts tested could be achieved. This method may be of significant importance in otologic research and microsurgical routine. In part 2, experimental animal results will follow, as the method portrayed was used to secure parts of a totally implantable middle ear hearing device.
An experimentally developed technique for microapplication of low-viscosity glass-ionomeric cement (see part 1) was tested in animals over a 6-month period. The cement was used to firmly connect gold with titanium and gold with middle ear ossicles in 22 adult foxhounds. After a 6-month period of acoustic stimulation via parts of an implantable hearing aid, the finely applied glass-ionomeric cement was integrated in situ, stable and caused no adverse reactions. The microapplication technique used proved to be easy, effective and provided long-term stability.
A retrospective analysis of diagnostic procedures and clinical outcome of patients with neurogenic tumours of the head and neck region was performed. There were 25 patients - 16 with neurinoma, 5 with neurofibroma and 4 with neurogenic sarcoma - who presented with a mass in the head and neck area. In 13 patients, the neurinoma originated from the facial nerve, 2 of them were located in the middle ear and mastoid and showed facial palsy. Four patients presented with neurofibromatosis type 1. Twenty-three patients were operated on to remove the tumorous masses. Eighteen tumours were assigned intraoperatively to a cranial nerve main trunk, whereas 7 tumours originated from small branches or showed diffuse growth in neurofibromatosis. All benign neurogenic tumours were removed totally without relapse. One of 2 auricular nerve autografts in middle-ear facial nerve neurinoma resulted in a sufficient muscle tonus of the face. Three patients with malignancies died within 12-24 months showing local recurrencies (n = 1) and/or pulmonary metastasis (n = 2). As expected, neurogenic tumours are unusual neoplasms of the head and neck regions. On the other hand, neurogenic malignancies exhibit diagnostic problems as well as uncertain chances for long-term survival. Tumour staging, determined by extension and critical for treatment decisions, is well evaluated by CT scan and MRI. A multimodal therapy regimen with operation and radiation is recommended for neurogenic sarcoma also when developing in neurofibromatosis. However, in main trunk neurinomas, nerve autografting with interposition is the therapy of choice with a good chance of functional recuperation.