[Anterolateral extension of the lateral suboccipital approach: an anatomical study].

We studied the extensions of the lateral suboccipital approach (LSOA) in seven cadaver heads, in the microsurgical laboratory, in order to establish the extensions necessary to approach the anterolateral area of the foramen magnum and the jugular foramen. The extensions (bone resection) were accomplished in five progressive steps: 1) suboccipital retrossigmoid craniectomy (LSOA retrocondylar); 2) extending the craniectomy with removal of half the occipital condyle (LSOA partial transcondylar); 3) extending the drilling of the occipital condyle to open the hypoglossal foramen, followed by removal of the jugular tubercle and opening the jugular foramen (LSOA transcondylar-transjugular); 4) complete drilling of the occipital condyle (LSOA complete transcondylar); 5) LSOA complete transcondylar plus removal of the atlas lateral mass up to the odontoid process (ASOL transcondylar-transjugular). We concluded that the extensions of LSOA should be adapted to the topography of the lesion: the LSOA retrocondylar for the lateral area of the foramen magnum; the LSOA partial transcondylar for the anterolateral portion; the LSOA transcondylar-transjugular to reach the jugular foramen; the LSOA complete transcondylar for the anterior part, and the LSOA complete transcondylar/translateral mass of the atlas for extradural lesions anterior to the foramen magnum.