**3.1 Anatomical access landmarks**

Pterion is one of the key landmarks of the MPA and the area of the burr hole placement (**Figure 11**). It is localized in the region of the temporal fossa and is a point at the junction of the parietal bone, the squamous part of the temporal bone, the greater wing of the sphenoid bone and the frontal bone. These bones in the region of the pterion are connected with a sphenoparietal, coronary and squamous suture. Immediately below the pterion, the anterior Sylvian point is located. This landmark is the most common for entry and further dissection of the Sylvian fissure, since the cistern of the Sylvian fissure is usually dilated in this area.
