Endoscopic Anatomical Study Of Anterior Clinoid Process And Its Adjacent Structures

Objective: The anterior clinoid process is a bony structure protruding backward from the end of the wing of the sphenoid bone,downward covering the optic nerve and ophthalmic artery in the optic canal,and clinoid segment of the internal carotid artery.The membranous structure of the anterior clinoid process is connected with the posterior clinoid process through the interclinoid ligament.The regional anatomical relationship of the above structures is complex and fragile,which should be protected during the operation.At the same time,the anterior clinoid process,as a capsular bony structure at the junction of the anterior and middle skull base,is a common site of many tumors and lesions.Its bone affects the operating space during the operation,and the safe removal of the anterior clinoid process is of great significance to the protection of important structures during the operation.this study increases the understanding of this area from a new point of view through the layer-by-layer anatomy of the anterior clinoid process and its adjacent structures in neuroendoscopic surgery.It is expected to be used as the basis for guiding the operation.Methods: In this study,the anterior clinoid process and its adjacent structures of 6 fresh cadaver heads(12 sides)were observed and photographed by transsphenoidal approach and pterional approach under endoscope,and the anterior clinoid process was removed by endoscope,and then the related data of the bony structure and adjacent structure of the anterior clinoid process were measured by craniotomy.The measured data were calculated and processed by spss 21.0 statistical software,and the results were expressed as mean ±standard deviation.Results: The anterior clinoid process is a bony process extending inward and posterior from the wing of sphenoid bone.The length of the bony part of the anterior clinoid process is 9.02 ±0.46 mm,the width is 11.02 ±0.68 mm,and the thickness of the base is5.34 ± 0.34 mm.The endoscopic grinding of the anterior clinoid process is 7.78 ±1.56 mm,9.75 ± 1.86 mm and 6.12 ± 1.24 mm respectively.The depth of the bottom surface is 5.24 ± 1.03 mm,and the length of the end is 2.02 ± 0.89 mm.The exposure length of anterior optic nerve was 8.52 ± 0.20 mm before anterior clinoid grinding,and18.15 ± 0.36 mm after grinding.The exposed length of anterior internal carotid artery was 9.14 ±0.55 mm,and it turns to 15.63 ±0.87 mm after grinding,and the length of interclinoid ligament was 4.83 ±0.33 mm.Conclusion: Endoscopic observation shows that the anterior clinoid process is wrapped by membranous tissue and covers the clinoid process segment of the optic nerve,ophthalmic artery and internal carotid artery downward.The position of the anterior clinoid process is deep and its structure is complex and crowded,so attention should be paid to the protection during the operation.Endoscopic transnasal approach and pterional approach have the possibility of safe removal of anterior clinoid process,which provides a theoretical basis for surgical resection of anterior clinoid process tumors,clipping of aneurysms and optic canal decompression.Endoscopic observation of the adjacent area of the anterior clinoid process shows that the oculomotor nerve and cavernous sinus and other related structures are closely related to it.Attention should be paid to the grinding depth in the operation of anterior clinoid meningioma and ophthalmic aneurysm to prevent thermal injury.