Key points

• When drilling behind the semicircular canal, it is important to use long brush strokes and to keep an even depth. This keeps a widely open valley. Run around the edges of this valley, deepening slightly and taking away the outer layer of the cortical bone.

• Do not allow the dissection to become too deep in one particular place.

• Drill along the dura, using long strokes running from anterior to posterior, or the reverse, depending on the handedness of the surgeon. Appropriate techniques include using often shorter and sharper brush strokes to define the plane of interest.

• Leave a very thin layer of bone over the dura and the sigmoid sinus. If you inadvertently uncover the dura, this is not usually a big problem provided the area that is left uncovered is relatively small. The same can be said for the sigmoid but the risks are of causing a bleed if you enter the sigmoid.

• Adjust the degree of water escaping from the sucker/irrigator so that the operative field is moist at all times.