The Study On The Microsurgical Anatomy Of Far Lateral Approach Of Posterior Cranial Fossa

Objective: The purpose of this study is to observe microsurgical anatomy of far lateral approach of posterior cranial fossa.Methods: 30(60 sides)adult dried skulls ,10(20 sides)adult cadaveric heads with connected neck fixed with 10% formalin,and another 15(30 sides) adult cadaveric heads were examined in this study .The important structures such as the foramen magnum,occipital condyle,hypoglossal canal were investigated on the dried skulls. The suboccipital segment of vertebral artery was dissected and measured on the cadaveric heads with connected neck according to the procedures of far lateral approach. The ventro-and ventrolateral brain stem was exposed after removing suboccipital skull and splitting dural.The relationship among the forth segment of the vertebral artery and the low cranial nerves was observed. The occipital condylewas drilled to the intracranial end of the hypoglossal canal from posterior lateral margin according to the procedures of far lateral approach under the surgical microscope(X4~10 magnification).Then the drilled length was measured . The skull was sawed off at the level of 6cm above the external occipital protuberance. The calvarium and cerebrum were removed. The brain stem and cerebella were reserved .Then the forth segment of the vertebral artery, the low cranial nerves and the structures of the ventro- marrow and the lower clival were observed and measured. Result:1. The occipital condyle was located at lateral side of the foramen magnum, the intracranial end of the hypoglossal canal was located above the junction of the posterior and middle one-third of the occipital condyle.The structures of ventro- foramen magnum region were exposed preferably when the occipital condyle was drilled to the the intracranial end of the hypoglossal canal. 2 The former branch of C2 nerve all crossed from the back of the suboccipital segment ofvertebral artery which was enclosed by either venous plexus or venous sinus and its length andcurve were various significantly.3.The encephalic segment of the vertebral artery tracked mostly in the front of the low cranialnerves.The posterior inferior cerebrellar artery send out from the vertebral artery and acrossedbetween the root of the low cranial nerves.4.Dural opened from front of the vertebral artery may avoid operation among the low cranialnerves and reduce the pull of brain stem.5. The olive had an intimacy relationship with the low cranial nerves.Conclusions:.The transverse process of the atlas was the important landmark foridentification of the vertebral artery.2.The cortex arounding the intracranial end of the hypoglossal canal can be seen as the landmarkfor arrival of the hypoglossal canal and estimate the resected extension of the occipital condyle.3.Study of microanatomy in the far lateral approach is helpful of resecting tumours of theventro- foramen magnum and the lower clival region and preserving important tissues.