Introduction. To achieve a functional atraumatic cochlear implantation, intracochlear pressure changes during the procedure should be minimized. Postinsertional cable movements are assumed to induce intracochlear pressure changes. The aim of this study was to observe intracochlear pressure changes due to postinsertional cable movements. Materials and Methods. Intracochlear pressure changes were recorded in a cochlear model with a micro-pressure sensor positioned in the apical region of the cochlea model to follow the maximum amplitude and pressure gain velocity in intracochlear pressure. A temporal bone mastoid cavity was attached to the model to simulate cable positioning. The compared conditions were (1) touching the unsealed electrode, (2) touching the sealed electrode, (3) cable storage with an unfixed cable, and (4) cable storage with a fixed cable. Results. We found statistically significant differences in the occurrence of maximum amplitude and pressure gain velocity in intracochlear pressure changes under the compared conditions. Comparing the cable storage conditions, a cable fixed mode offers significantly lower maximum pressure amplitude and pressure gain velocity than the nonfixed mode. Conclusion. Postinsertional cable movement led to a significant pressure transfer into the cochlea. Before positioning the electrode cable in the mastoid cavity, fixation of the cable is recommended.

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A New Axial Centre of Gd3+ in Hexagonal CdS BY Sonderforschungsbereich Elektronische Eigenschaften fester Korper , W. URBAN, J. LUGER, R. MELCHERS, andG. mLLER-VOGT Various spectra of trivalent gadolinium in hexagonal CdS have been reported in the past (1, 2). Two spectra of axial symmetry have been assigned in a different way by Kemp and Schehl et al. (1, 2) to a substitutional and an interstitial lattice site. A centre of orthorhombic symmetry has also been found (1). Other trivalent Short Notes K115 with A = 104 MHz, B = 72 K as fitting parameters and 3 ( 0 ) = 11716 MHz.As f a r a s the determination of the site of the gadolinium centres is concerned, we can only say that it has axial symmetry and it might a s well be the %ubstitutional" site a s one of the others reported in (1, 2). On the other hand, the strong splittings (5) quoted before, occur for gadolinium-hydrogen pairs in CaF This suggests the possibility that the observed spectrum in CdS is also due to an ion associated with gadolinium. 2'