AMONG OTHERS, Schlöndorff et al¹ introduced 3-dimensional (3-D) navigation to otolaryngology in 1987 with a position-sensitive articulated arm. A successor thereof was the ISG Viewing Wand, which was for sometime considered the criterion standard in 3-D navigation. After initial scepticism of otolaryngologists, 3-D navigation emerged as an accepted and useful technique in nasal, paranasal, and skull base surgery. Minimally invasive surgery has gained enormous popularity because delicate structures at risk can be identified safely even when reliable landmarks are missing (tumors, revision, bleeding, etc).^1-5 We have gained experience with different 3-D navigation systems in approximately 250 operations mainly at the paranasal sinuses and the frontal and lateral skull bases. We report some aspects of our work with 3-D navigation systems, emphasizing those that are crucial to obtaining optimal intraoperative results.

Summary: The combination of osmium tetroxide staining and high‐resolution tomographic imaging using monochromatic X rays allows visualizing cellular structures of the human inner ear, that is, the organ of Corti, the stria vascularis and further soft tissues of the membranous labyrinth, in three‐dimensional space with isotropic micrometre resolution. This approach permits to follow the course of nerve fibre bundles in a major part of the specimen and reveals the detailed three‐dimensional arrangement of individual ganglion cells with distinct nuclei by means of X‐ray tomography for the first time. The non‐destructive neuron cell counting in a selected volume of 125 μm × 800 μm × 600 μm = 0.06 mm³ gives rise to the estimate that 2000 ganglion cells are present along 1 mm organ of Corti.