Anatomy of the optic chiasma and its surrounding structures in saddle area operation

Objective To provide morphological evidences for visual field defect caused by the compression of the saddle area tumors.Methods The shape and position of the optic chiasma and its surrounding saddle diaphragm,pituitary,internal carotid artery,and perforating arteries of optic chiasma were studied from 80 adult.Results Its maximum angle was 100° in anterior horn with prechiasmatic space, and minimum angle was 40° with postfixed optic chiasma.The area of optic chiasma averaged(1.32±0.04)cm2,the thickness of saddle diaphragm was 0.58 mm,and about 5% of saddie diaphragm did not exist.The foramen of saddle diaphragm pushed into the opposite side was 52.5%,and the maximum diameter was 7.8 mm×9.8 mm.The pituitary was found inferior to the saddle diaphragm foramen in 78%(62/80).In 76.3%(61/80) brains,the carotid artery touched chiasm opticum.Conclusions Visual field defect caused by compression from pituitary tumor and craniopharyngioma is directly related with the shape of the optic chiasma and its surrounding structures. Key words: Saddle area tumors; Optic chiasma