The Study On The Surgical Anatomy Of Far Lateral Approach Of Skull Base

Objective:The purpose of this anatomical study is to explore themorphological characteristics of tissues and structures in the suboccipital area associated with the far lateral approach.Methods: 30 adult dried skulls, 15 adult cadaveric heads fixedwith 10% formalin, and another 10 adult cadaveric heads with connected neck were used in this study. The relationship among the occipital condyle, the foramen magnum, hypoglossal canal and jugular tubercle was investigated on the dried skulls. Various anatomical structures were dissected . The distance between these structures and the underlying venous sinus was measured on the cadaveric heads. Using ×4.5 loupes magnification, the occipital condyle was dilled to the intracranial end of the hypoglossal canal from posterior laterior margin according to the procedures of far lateral approach, then the length of remainder was measured. The suboccipital segment of vertebral artery and related structures were dissected and measured on the cadaveric heads with connected neck under ×4.5 loupes magnification.Results: 1. The asterion wasn' t always located over the superficialsurface of the transverse-sigmoid sinus junction. The apex of the superior nuchal line was above the very proximal transverse sinusin most case, while the point of occipital insert of the musculus semispinalis capitus was below it. The point of occipital insert of the musculus splenius capitus posterior to the mastoid was located inferior and medial to the transverse-sigmoid sinus junction. The inion was located inferior to the torcular herophili.2. The intracranial end of the hypoglossal canal was located above the junction of the posterior and middle one-third of the occipital condyle. The distance between the occipital condyle and the extracranial end of jugular foramem on the right sides was shorter than the left sides.3. The suboccipital segment of vertebral artery was enclosed by either Venous plexus or venous sinus. Its length and curve were various significantly. Most of its branches were originated from its medial surface.4. The occipital artery coursed under the longissimus capitis muscle in 60% cases and superficially in 40% cases.5. The cervical nerves pierced their innervating muscles of suboccipital region near their attachments to the occipital bone laterally.Conclusions: 1. It is helpful of using the occipital inserts ofmusculus semispinalis capitus and splenius capitus as the superficial landmarks of the underlying venous sinuses to reduce potential damage during far lateral approach. 2. It is helpful of knowing the anatomical characteristics of tissues and structures in the suboccipital area to preserve the important structures duringfar lateral approach.