Figure 1: Screenshot of the surgical planning environment (specimen: human left temporal bone. software: iPlan ® ENT 2.5, BrainLAB, Feldkirchen, Germany, sagittal reformation). fn: facial nerve, ct: chorda tympani, sc: semicircular canal, hm: head of the malleus, ib: body of the incus. The pink circle in the middle of the upper picture signifies the axis of the trajectory.