Measurement of middle ear transfer function in temporal bones using electromagnetic excitation: Comparison to sound excitation and evaluation of influencing factors.

Hearing a sound produces vibrations of the ossicles in the middle ear, which can be measured in the micrometer to nanometer range. Destruction of middle ear structures results most commonly from chronic inflammatory diseases. In these cases, passive and active middle ear implants are used for reconstruction of the ossicular chain. The positioning of the implants depends primarily on the surgeon's experience. So far, no objective assessment has been conducted to affirm if the chosen positioning is the best in each specific case. We have established a new method, allowing us to measure the middle ear transfer function (METF) intraoperatively. Using the new method, a magnet is placed on the umbo of the malleus handle and is stimulated by a coil positioned underneath the head. The resulting vibration is measured on the stapes footplate using Laser Doppler vibrometry (LDV). Acoustic and electromagnetic excitation show comparable METF in lower frequencies, which differ up to 10 dB in frequencies over 1 kHz. The position of the coil does not play a relevant part in the METF, whereas the location of the magnet on the tympanic membrane highly impacts the METF. This technique demonstrates reproducible results. Electromagnetic excitation is comparable to sound excitation and is suited for measuring the METF. A stable positioning of the magnet on the umbo is essential in order to acquire valid data.

Trends in Incidence Rates during 1999-2008 and Prevalence in 2008 of Childhood Type 1 Diabetes Mellitus in Germany--Model-Based National Estimates.

AIMS: To estimate the national incidence rate and trend of type 1 diabetes (T1DM) in Germany from 1999 to 2008 and the national prevalence in 2008 in the age group 0-14 years. METHODS: Data were taken from a nationwide registry for incident cases of T1DM in the ages 0-4 years and 3 regional registries (North-Rhine-Westphalia, Baden-Wuerttemberg and Saxony) for incident cases of T1DM in the ages 0-14 years covering 41% of the child population in Germany. The degree of ascertainment was ≥ 97% in all registries. Incident and prevalent cases were grouped by region, sex, age (0-4, 5-9, 10-14 years), and, for incident data, additionally by two 5-year periods (1999-2003, 2004-2008). Poisson regression models were fitted to the data to derive national estimates of incidence rate trends and prevalence in the age groups 5-9, 10-14 and 0-14 years. We used direct age-standardization. RESULTS: The estimated national incidence rate in 0-14-year-olds increased significantly by 18.1% (95%CI: 11.6-25.0%, p<0.001) from 1999-2003 to 2004-2008, independent of sex, corresponding to an average annual increase of 3.4% (95%-CI: 2.2-4.6%). The overall incidence rate was estimated at 22.9 per 100,000 person-years and we identified a within-country west-east-gradient previously unknown. The national prevalence in the ages 0-14 years on 31/12/2008 was estimated to be 148.1 per 100,000 persons. CONCLUSIONS: The national incidence rate of childhood T1DM in Germany is higher than in many other countries around the world. Importantly, the estimated trend of the incidence rate confirms the international data of a global increase of T1DM incidences.