Use largest burr

Select the largest burr that will fit into the site easily. Use a sweeping action that is as long as possible. When completing landmarks see that it will be possible to execute a sweeping action along the length of the next structure to be identified. In this way you will detect any irregularities and its curvilinear nature.

Small areas of the dura may be exposed by this technique but the drill will not penetrate it. Gain the confidence that with this technique the position and depth of most the next structure will be apparent well before the structure itself is visible. In practice the dura is often exposed deliberately to determine the thickness of the cortical bone in the region. It is not acceptable to expose the skin of the bony ear canal, or the lateral semicircular canal.

The facial nerve should only be exposed when the dissection is prepared for this step.