Microsurgical anatomical landmarks concerning to suboccipital far lateral approach

Objective To observe microsurgical anatomy of anatomical landmarks concerning to suboccipital far lateral approach. Methods Totally 30 (60 sides) adult dried skulls, 10 (20 sides) adult cadaveric heads with connected neck fixed in 10% formalin, and another 15 (30 sides) adult cadaveric heads were collected. The important structures such as 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 occipital condyle was 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 (4-10). Then the drilled length was measured. Results ①The 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 intracranial end of the hypoglossal canal. ②The former branch of C2 nerve all crossed from the back of the suboccipital segment of vertebral artery which was enclosed by either venous plexus or venous sinus and its length and curve were various significantly. ③Dural opened from front of the vertebral artery may avoid operation among the low cranial nerves and reduce the pull of brain stem. Conclusion Study of microanatomy in the far lateral approach is helpful of resecting tumors of the ventro-foramen magnum and the lower clival region and preserving important tissues.