Abstract: Objective　To observe the anatomical structure of the first denticulate ligament at the craniocervical junction and to discuss its clinical significance.    Methods    Eighteen cranial-neck specimens were dissected and were stripped to observe the structure of the first denticulate ligament. Its starting and finishing, adjacency, course and its morphology were observed.  The histological characteristics of the ligament was detected by HE staining.　Results　The first denticulate ligament were found in left and right side of all specimens (occurrence rate: 100%), with the membrane type in 9 cases (accounting for 50%); dense type in 4 cases (accounting for 22.2%); loose type in 5 cases (accounting for 27.8%). The first denticulate ligament was located laterally to the superior medulla oblongata, the fibers converged outwards and upward in a long triangle, crossing behind the vertebral artery and ending in the epidural and fusing with the dura mater. The attachment part on the spinal cord was located between the anterior root and posterior root of the spinal nerve, the distal part was integrated with the 2nd ~ 8th dentate ligament, and the proximal part reached the level of the medulla oblongata. Histological result showed that the denticulate ligament was composed of collagen fibers.   Conclusions　The first denticulate ligament plays an important role in maintaining the stability of the spinal cord. Subarachnoid space is divided into a front part and a back part by denticulate ligament. Cerebrospinal fluid pressure imbalance can lead to different stress on the anterior and posterior parts of the spinal cord. And the anterior spinal cord may be subjected to higher pressure stimulation to aggravate or induce the injury of the anterior horn cells of the spinal cord and the corticospinal tract, which may be one of the anatomical factors leading to amyotrophic lateral sclerosis (ALS).

Key words: Denticulate ligament, 　Amyotrophic lateral sclerosis;　Craniocervical junction