[Morphometric characteristics of the asterion and the posterolateral surface of the skull: its relationship with dural venous sinuses and its neurosurgical importance].

BACKGROUND The knowledge of the location and morphometric of the lateral venous sinus (transverse and sigmoid), and their relationship with the asterion and other surface anatomical landmarks, it is imperative for posterolateral approaches to the posterior cranial fossa to avoid vascular structures injury and surgical complications. OBJECTIVE Determine an anatomical area security for a drill that allows entry into the posterior cranial fossa without damaging adjacent structures, and study the morphometric characteristics asterion, the lateral sinus and bony landmarks of the posterolateral surface of the skull. METHODS With a 1.3 mm drill drilled both sides of 88 dry skulls (176 hemicranias). The anatomical landmarks studied were the asterion, the apex of the mastoid process, spina suprameatal, the Frankfurt horizontal plane, the posterior root of the zygomatic arch, the external occipital protuberance and its relationship with the sinus transversus. RESULTS The asterion type I prevails in 74.4% of the pieces. In 82.4% of the skulls asterion level is, sinus transversus in less than 12.5% and above this at 5.1%. CONCLUSIONS With the data obtained from this and other research, the initial trephine should be placed below the 15 mm and 15 mm asterion post this to reduce the risk of injury from sinus transversus.