We evaluated the transport of Gadolinium-diethylenetriaminepentaacetate-bismethylamide (Gd-DTPA-BMA) through the round window (RW) membrane into the perilymphatic space with 4.7-T MRI in an animal study and 1.5-T MRI in humans. After administration of Gd-DTPA-BMA onto the intact RW membrane of guinea pig, Gd-DTPA-BMA uptake was observed in the basal turn and part of the second turn within 40 min. The scala tympani, scala vestibuli, the fibrous part of the spiral ligament and semicircular canal all showed uptake of Gd-DTPA-BMA. All turns of the cochlea were filled with Gd within 10 min in the perforated RW membrane administration group and within 30 min in the intravenous administration group. In patients who accepted middle ear injection of Gd-DTPA-BMA, uptake was observed within 2 h in the basal turn and semicircular canal. After 12 h the apex did still not show any uptake. Gd-DTPA-BMA is transported from the RW to the semicircular canal, the scala tympani and scala vestibuli without passing the helicotrema.

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The purpose of the study was to evaluate the effect of noise, age and confounders in noise-induced hearing loss (NIHL). Information about work exposure, the use of hearing protective devices, audiogram, environmental and biological factors was collected from 406 paper mill workers exposed to noise levels of 91-94 dB(A), 124 forest workers exposed to noise levels of 96-99 dB(A) and 176 shipyard workers exposed to noise levels 95-97 dB(A). In addition to noise exposure, we collected the following confounders: smoking habits, serum cholesterol, systolic or diastolic blood pressure and use of analgesics. Subjects were classified based on median values, into high- and low-risk groups. The confounders were a significant source of hearing loss (HL) in younger and elderly groups of subjects, serum cholesterol level being the most important. In risk analysis the confounders partly masked the effects of noise in the development of HL. For subjects with less than two confounders, occupational noise exposure determined the development of NIHL. As the number of confounders increased, the noise exposure was overruled by these factors in the development of HL. In analysis where the subjects were matched with pairs by age, exposure, blood pressure and serum cholesterol level, the elderly subjects were more susceptible to NIHL than younger subjects. Factors independently but causally related to age were important in the development of NIHL among workers exposed to noise levels below 98 dB(A).

We have investigated the feasibility to use posturography as a method to estimate sleep deprivation. This manuscript presents a proof-of-concept of this idea. Twenty-one healthy subjects aged 20-37 years participated in the study. The subjects were deprived of sleep for up to 36 h. Their postural stability was measured as a function of sleep deprivation time. As a reference the critical fusion frequency method for measuring sleepiness was used. The 163 posturographic parameters used for analyzing the posturographic data were found from the literature. Of these parameters, the fractal dimension of the sway path, the most common frequency of the sway, the time-interval for open-loop control of stance, and the most common amplitude of the sway showed the highest linear correlations with sleep deprivation time. Using these four parameters we were able to estimate the sleep deprivation time with an accuracy better than 5 h for 80% of the subjects.

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