[Microsurgical anatomy of craniocervical junction region]

To study the shape and the structures in the craniocervical junction region (CCJR) and the safety of far lateral approach.

Ten cadaveric heads and 20 skull-base specimens were fixed with 10% formalin, and 4 of the 10 cadaveric heads were sectioned in different plane with the aid of operative microscope. The shape and relation of structures in the CCJR were observed.

The third segment of the vertebral artery(VA) was 21.6(15.3 31.9) mm. An incomplete bony canal was found to be 15% and complete bony canal surrounding the VA to be 5% on the VA groove. The distance of the left and right VA was 14.3a(c)(9.8 15.2) mm on the entry into the dura. The length of the occipital condyle was 26.8(25.1 28.2) mm, with the thickness of its anterior, middle and posterior one-third part was 9.9(9.6 10.6) mm, 11.2(9.2 13.1) mm and 8.6 (8.3 9.0) mm respectively. The distance between the posterior pole of the occipital condyle and the intracranial orifice of the hypoglossal canal was 9.9(8.6 11.4) mm, and between the posterior pole and the extracranial orifice was 16.1(13.5 17.1) mm. The transverse process of the atlas was the most important bony landmark for the approach.

Knowing the shape and relationship of the VA and occipital condyle in the CCJR is helpful in preserving the important structures in far lateral approach to target region.